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  21 <title>Chapter 6. BIND 9 Configuration Reference</title>
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  31 <tr><th colspan="3" align="center">Chapter 6. <acronym class="acronym">BIND</acronym> 9 Configuration Reference</th></tr>
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  42 <div class="chapter" lang="en">
  43 <div class="titlepage"><div><div><h2 class="title">
  44 <a name="Bv9ARM.ch06"></a>Chapter 6. <acronym class="acronym">BIND</acronym> 9 Configuration Reference</h2></div></div></div>
  45 <div class="toc">
  46 <p><b>Table of Contents</b></p>
  47 <dl>
  48 <dt><span class="sect1"><a href="Bv9ARM.ch06.html#configuration_file_elements">Configuration File Elements</a></span></dt>
  49 <dd><dl>
  50 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#address_match_lists">Address Match Lists</a></span></dt>
  51 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2573945">Comment Syntax</a></span></dt>
  52 </dl></dd>
  53 <dt><span class="sect1"><a href="Bv9ARM.ch06.html#Configuration_File_Grammar">Configuration File Grammar</a></span></dt>
  54 <dd><dl>
  55 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574531"><span><strong class="command">acl</strong></span> Statement Grammar</a></span></dt>
  56 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#acl"><span><strong class="command">acl</strong></span> Statement Definition and
  57           Usage</a></span></dt>
  58 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574789"><span><strong class="command">controls</strong></span> Statement Grammar</a></span></dt>
  59 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage"><span><strong class="command">controls</strong></span> Statement Definition and
  60           Usage</a></span></dt>
  61 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575148"><span><strong class="command">include</strong></span> Statement Grammar</a></span></dt>
  62 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575165"><span><strong class="command">include</strong></span> Statement Definition and
  63           Usage</a></span></dt>
  64 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575189"><span><strong class="command">key</strong></span> Statement Grammar</a></span></dt>
  65 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575212"><span><strong class="command">key</strong></span> Statement Definition and Usage</a></span></dt>
  66 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575303"><span><strong class="command">logging</strong></span> Statement Grammar</a></span></dt>
  67 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575429"><span><strong class="command">logging</strong></span> Statement Definition and
  68           Usage</a></span></dt>
  69 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577496"><span><strong class="command">lwres</strong></span> Statement Grammar</a></span></dt>
  70 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577570"><span><strong class="command">lwres</strong></span> Statement Definition and Usage</a></span></dt>
  71 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577702"><span><strong class="command">masters</strong></span> Statement Grammar</a></span></dt>
  72 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577746"><span><strong class="command">masters</strong></span> Statement Definition and
  73           Usage</a></span></dt>
  74 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577761"><span><strong class="command">options</strong></span> Statement Grammar</a></span></dt>
  75 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#options"><span><strong class="command">options</strong></span> Statement Definition and
  76           Usage</a></span></dt>
  77 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#server_statement_grammar"><span><strong class="command">server</strong></span> Statement Grammar</a></span></dt>
  78 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#server_statement_definition_and_usage"><span><strong class="command">server</strong></span> Statement Definition and
  79             Usage</a></span></dt>
  80 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#statschannels"><span><strong class="command">statistics-channels</strong></span> Statement Grammar</a></span></dt>
  81 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2588166"><span><strong class="command">statistics-channels</strong></span> Statement Definition and
  82             Usage</a></span></dt>
  83 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#trusted-keys"><span><strong class="command">trusted-keys</strong></span> Statement Grammar</a></span></dt>
  84 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2588374"><span><strong class="command">trusted-keys</strong></span> Statement Definition
  85             and Usage</a></span></dt>
  86 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2588421"><span><strong class="command">managed-keys</strong></span> Statement Grammar</a></span></dt>
  87 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#managed-keys"><span><strong class="command">managed-keys</strong></span> Statement Definition
  88             and Usage</a></span></dt>
  89 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#view_statement_grammar"><span><strong class="command">view</strong></span> Statement Grammar</a></span></dt>
  90 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2588915"><span><strong class="command">view</strong></span> Statement Definition and Usage</a></span></dt>
  91 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#zone_statement_grammar"><span><strong class="command">zone</strong></span>
  92             Statement Grammar</a></span></dt>
  93 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2590556"><span><strong class="command">zone</strong></span> Statement Definition and Usage</a></span></dt>
  94 </dl></dd>
  95 <dt><span class="sect1"><a href="Bv9ARM.ch06.html#id2593224">Zone File</a></span></dt>
  96 <dd><dl>
  97 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#types_of_resource_records_and_when_to_use_them">Types of Resource Records and When to Use Them</a></span></dt>
  98 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2595454">Discussion of MX Records</a></span></dt>
  99 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#Setting_TTLs">Setting TTLs</a></span></dt>
 100 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2596070">Inverse Mapping in IPv4</a></span></dt>
 101 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2596197">Other Zone File Directives</a></span></dt>
 102 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2596470"><acronym class="acronym">BIND</acronym> Master File Extension: the  <span><strong class="command">$GENERATE</strong></span> Directive</a></span></dt>
 103 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#zonefile_format">Additional File Formats</a></span></dt>
 104 </dl></dd>
 105 <dt><span class="sect1"><a href="Bv9ARM.ch06.html#statistics">BIND9 Statistics</a></span></dt>
 106 <dd><dl><dt><span class="sect2"><a href="Bv9ARM.ch06.html#statistics_counters">Statistics Counters</a></span></dt></dl></dd>
 107 </dl>
 108 </div>
 109 <p>
 110       <acronym class="acronym">BIND</acronym> 9 configuration is broadly similar
 111       to <acronym class="acronym">BIND</acronym> 8; however, there are a few new
 112       areas
 113       of configuration, such as views. <acronym class="acronym">BIND</acronym>
 114       8 configuration files should work with few alterations in <acronym class="acronym">BIND</acronym>
 115       9, although more complex configurations should be reviewed to check
 116       if they can be more efficiently implemented using the new features
 117       found in <acronym class="acronym">BIND</acronym> 9.
 118     </p>
 119 <p>
 120       <acronym class="acronym">BIND</acronym> 4 configuration files can be
 121       converted to the new format
 122       using the shell script
 123       <code class="filename">contrib/named-bootconf/named-bootconf.sh</code>.
 124     </p>
 125 <div class="sect1" lang="en">
 126 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
 127 <a name="configuration_file_elements"></a>Configuration File Elements</h2></div></div></div>
 128 <p>
 129         Following is a list of elements used throughout the <acronym class="acronym">BIND</acronym> configuration
 130         file documentation:
 131       </p>
 132 <div class="informaltable"><table border="1">
 133 <colgroup>
 134 <col>
 135 <col>
 136 </colgroup>
 137 <tbody>
 138 <tr>
 139 <td>
 140                 <p>
 141                   <code class="varname">acl_name</code>
 142                 </p>
 143               </td>
 144 <td>
 145                 <p>
 146                   The name of an <code class="varname">address_match_list</code> as
 147                   defined by the <span><strong class="command">acl</strong></span> statement.
 148                 </p>
 149               </td>
 150 </tr>
 151 <tr>
 152 <td>
 153                 <p>
 154                   <code class="varname">address_match_list</code>
 155                 </p>
 156               </td>
 157 <td>
 158                 <p>
 159                   A list of one or more
 160                   <code class="varname">ip_addr</code>,
 161                   <code class="varname">ip_prefix</code>, <code class="varname">key_id</code>,
 162                   or <code class="varname">acl_name</code> elements, see
 163                   <a href="Bv9ARM.ch06.html#address_match_lists" title="Address Match Lists">the section called &#8220;Address Match Lists&#8221;</a>.
 164                 </p>
 165               </td>
 166 </tr>
 167 <tr>
 168 <td>
 169                 <p>
 170                   <code class="varname">masters_list</code>
 171                 </p>
 172               </td>
 173 <td>
 174                 <p>
 175                   A named list of one or more <code class="varname">ip_addr</code>
 176                   with optional <code class="varname">key_id</code> and/or
 177                   <code class="varname">ip_port</code>.
 178                   A <code class="varname">masters_list</code> may include other
 179                   <code class="varname">masters_lists</code>.
 180                 </p>
 181               </td>
 182 </tr>
 183 <tr>
 184 <td>
 185                 <p>
 186                   <code class="varname">domain_name</code>
 187                 </p>
 188               </td>
 189 <td>
 190                 <p>
 191                   A quoted string which will be used as
 192                   a DNS name, for example "<code class="literal">my.test.domain</code>".
 193                 </p>
 194               </td>
 195 </tr>
 196 <tr>
 197 <td>
 198                 <p>
 199                   <code class="varname">namelist</code>
 200                 </p>
 201               </td>
 202 <td>
 203                 <p>
 204                   A list of one or more <code class="varname">domain_name</code>
 205                   elements.
 206                 </p>
 207               </td>
 208 </tr>
 209 <tr>
 210 <td>
 211                 <p>
 212                   <code class="varname">dotted_decimal</code>
 213                 </p>
 214               </td>
 215 <td>
 216                 <p>
 217                   One to four integers valued 0 through
 218                   255 separated by dots (`.'), such as <span><strong class="command">123</strong></span>,
 219                   <span><strong class="command">45.67</strong></span> or <span><strong class="command">89.123.45.67</strong></span>.
 220                 </p>
 221               </td>
 222 </tr>
 223 <tr>
 224 <td>
 225                 <p>
 226                   <code class="varname">ip4_addr</code>
 227                 </p>
 228               </td>
 229 <td>
 230                 <p>
 231                   An IPv4 address with exactly four elements
 232                   in <code class="varname">dotted_decimal</code> notation.
 233                 </p>
 234               </td>
 235 </tr>
 236 <tr>
 237 <td>
 238                 <p>
 239                   <code class="varname">ip6_addr</code>
 240                 </p>
 241               </td>
 242 <td>
 243                 <p>
 244                   An IPv6 address, such as <span><strong class="command">2001:db8::1234</strong></span>.
 245                   IPv6 scoped addresses that have ambiguity on their
 246                   scope zones must be disambiguated by an appropriate
 247                   zone ID with the percent character (`%') as
 248                   delimiter.  It is strongly recommended to use
 249                   string zone names rather than numeric identifiers,
 250                   in order to be robust against system configuration
 251                   changes.  However, since there is no standard
 252                   mapping for such names and identifier values,
 253                   currently only interface names as link identifiers
 254                   are supported, assuming one-to-one mapping between
 255                   interfaces and links.  For example, a link-local
 256                   address <span><strong class="command">fe80::1</strong></span> on the link
 257                   attached to the interface <span><strong class="command">ne0</strong></span>
 258                   can be specified as <span><strong class="command">fe80::1%ne0</strong></span>.
 259                   Note that on most systems link-local addresses
 260                   always have the ambiguity, and need to be
 261                   disambiguated.
 262                 </p>
 263               </td>
 264 </tr>
 265 <tr>
 266 <td>
 267                 <p>
 268                   <code class="varname">ip_addr</code>
 269                 </p>
 270               </td>
 271 <td>
 272                 <p>
 273                   An <code class="varname">ip4_addr</code> or <code class="varname">ip6_addr</code>.
 274                 </p>
 275               </td>
 276 </tr>
 277 <tr>
 278 <td>
 279                 <p>
 280                   <code class="varname">ip_port</code>
 281                 </p>
 282               </td>
 283 <td>
 284                 <p>
 285                   An IP port <code class="varname">number</code>.
 286                   The <code class="varname">number</code> is limited to 0
 287                   through 65535, with values
 288                   below 1024 typically restricted to use by processes running
 289                   as root.
 290                   In some cases, an asterisk (`*') character can be used as a
 291                   placeholder to
 292                   select a random high-numbered port.
 293                 </p>
 294               </td>
 295 </tr>
 296 <tr>
 297 <td>
 298                 <p>
 299                   <code class="varname">ip_prefix</code>
 300                 </p>
 301               </td>
 302 <td>
 303                 <p>
 304                   An IP network specified as an <code class="varname">ip_addr</code>,
 305                   followed by a slash (`/') and then the number of bits in the
 306                   netmask.
 307                   Trailing zeros in a <code class="varname">ip_addr</code>
 308                   may omitted.
 309                   For example, <span><strong class="command">127/8</strong></span> is the
 310                   network <span><strong class="command">127.0.0.0</strong></span> with
 311                   netmask <span><strong class="command">255.0.0.0</strong></span> and <span><strong class="command">1.2.3.0/28</strong></span> is
 312                   network <span><strong class="command">1.2.3.0</strong></span> with netmask <span><strong class="command">255.255.255.240</strong></span>.
 313                 </p>
 314                 <p>
 315                   When specifying a prefix involving a IPv6 scoped address
 316                   the scope may be omitted.  In that case the prefix will
 317                   match packets from any scope.
 318                 </p>
 319               </td>
 320 </tr>
 321 <tr>
 322 <td>
 323                 <p>
 324                   <code class="varname">key_id</code>
 325                 </p>
 326               </td>
 327 <td>
 328                 <p>
 329                   A <code class="varname">domain_name</code> representing
 330                   the name of a shared key, to be used for transaction
 331                   security.
 332                 </p>
 333               </td>
 334 </tr>
 335 <tr>
 336 <td>
 337                 <p>
 338                   <code class="varname">key_list</code>
 339                 </p>
 340               </td>
 341 <td>
 342                 <p>
 343                   A list of one or more
 344                   <code class="varname">key_id</code>s,
 345                   separated by semicolons and ending with a semicolon.
 346                 </p>
 347               </td>
 348 </tr>
 349 <tr>
 350 <td>
 351                 <p>
 352                   <code class="varname">number</code>
 353                 </p>
 354               </td>
 355 <td>
 356                 <p>
 357                   A non-negative 32-bit integer
 358                   (i.e., a number between 0 and 4294967295, inclusive).
 359                   Its acceptable value might further
 360                   be limited by the context in which it is used.
 361                 </p>
 362               </td>
 363 </tr>
 364 <tr>
 365 <td>
 366                 <p>
 367                   <code class="varname">path_name</code>
 368                 </p>
 369               </td>
 370 <td>
 371                 <p>
 372                   A quoted string which will be used as
 373                   a pathname, such as <code class="filename">zones/master/my.test.domain</code>.
 374                 </p>
 375               </td>
 376 </tr>
 377 <tr>
 378 <td>
 379                 <p>
 380                   <code class="varname">port_list</code>
 381                 </p>
 382               </td>
 383 <td>
 384                 <p>
 385                   A list of an <code class="varname">ip_port</code> or a port
 386                   range.
 387                   A port range is specified in the form of
 388                   <strong class="userinput"><code>range</code></strong> followed by
 389                   two <code class="varname">ip_port</code>s,
 390                   <code class="varname">port_low</code> and
 391                   <code class="varname">port_high</code>, which represents
 392                   port numbers from <code class="varname">port_low</code> through
 393                   <code class="varname">port_high</code>, inclusive.
 394                   <code class="varname">port_low</code> must not be larger than
 395                   <code class="varname">port_high</code>.
 396                   For example,
 397                   <strong class="userinput"><code>range 1024 65535</code></strong> represents
 398                   ports from 1024 through 65535.
 399                   In either case an asterisk (`*') character is not
 400                   allowed as a valid <code class="varname">ip_port</code>.
 401                 </p>
 402               </td>
 403 </tr>
 404 <tr>
 405 <td>
 406                 <p>
 407                   <code class="varname">size_spec</code>
 408                 </p>
 409               </td>
 410 <td>
 411                 <p>
 412                   A number, the word <strong class="userinput"><code>unlimited</code></strong>,
 413                   or the word <strong class="userinput"><code>default</code></strong>.
 414                 </p>
 415                 <p>
 416                   An <code class="varname">unlimited</code> <code class="varname">size_spec</code> requests unlimited
 417                   use, or the maximum available amount. A <code class="varname">default size_spec</code> uses
 418                   the limit that was in force when the server was started.
 419                 </p>
 420                 <p>
 421                   A <code class="varname">number</code> can optionally be
 422                   followed by a scaling factor:
 423                   <strong class="userinput"><code>K</code></strong> or <strong class="userinput"><code>k</code></strong>
 424                   for kilobytes,
 425                   <strong class="userinput"><code>M</code></strong> or <strong class="userinput"><code>m</code></strong>
 426                   for megabytes, and
 427                   <strong class="userinput"><code>G</code></strong> or <strong class="userinput"><code>g</code></strong> for gigabytes,
 428                   which scale by 1024, 1024*1024, and 1024*1024*1024
 429                   respectively.
 430                 </p>
 431                 <p>
 432                   The value must be representable as a 64-bit unsigned integer
 433                   (0 to 18446744073709551615, inclusive).
 434                   Using <code class="varname">unlimited</code> is the best
 435                   way
 436                   to safely set a really large number.
 437                 </p>
 438               </td>
 439 </tr>
 440 <tr>
 441 <td>
 442                 <p>
 443                   <code class="varname">yes_or_no</code>
 444                 </p>
 445               </td>
 446 <td>
 447                 <p>
 448                   Either <strong class="userinput"><code>yes</code></strong> or <strong class="userinput"><code>no</code></strong>.
 449                   The words <strong class="userinput"><code>true</code></strong> and <strong class="userinput"><code>false</code></strong> are
 450                   also accepted, as are the numbers <strong class="userinput"><code>1</code></strong>
 451                   and <strong class="userinput"><code>0</code></strong>.
 452                 </p>
 453               </td>
 454 </tr>
 455 <tr>
 456 <td>
 457                 <p>
 458                   <code class="varname">dialup_option</code>
 459                 </p>
 460               </td>
 461 <td>
 462                 <p>
 463                   One of <strong class="userinput"><code>yes</code></strong>,
 464                   <strong class="userinput"><code>no</code></strong>, <strong class="userinput"><code>notify</code></strong>,
 465                   <strong class="userinput"><code>notify-passive</code></strong>, <strong class="userinput"><code>refresh</code></strong> or
 466                   <strong class="userinput"><code>passive</code></strong>.
 467                   When used in a zone, <strong class="userinput"><code>notify-passive</code></strong>,
 468                   <strong class="userinput"><code>refresh</code></strong>, and <strong class="userinput"><code>passive</code></strong>
 469                   are restricted to slave and stub zones.
 470                 </p>
 471               </td>
 472 </tr>
 473 </tbody>
 474 </table></div>
 475 <div class="sect2" lang="en">
 476 <div class="titlepage"><div><div><h3 class="title">
 477 <a name="address_match_lists"></a>Address Match Lists</h3></div></div></div>
 478 <div class="sect3" lang="en">
 479 <div class="titlepage"><div><div><h4 class="title">
 480 <a name="id2573643"></a>Syntax</h4></div></div></div>
 481 <pre class="programlisting"><code class="varname">address_match_list</code> = address_match_list_element ;
 482   [<span class="optional"> address_match_list_element; ... </span>]
 483 <code class="varname">address_match_list_element</code> = [<span class="optional"> ! </span>] (ip_address [<span class="optional">/length</span>] |
 484    key key_id | acl_name | { address_match_list } )
 485 </pre>
 486 </div>
 487 <div class="sect3" lang="en">
 488 <div class="titlepage"><div><div><h4 class="title">
 489 <a name="id2573671"></a>Definition and Usage</h4></div></div></div>
 490 <p>
 491             Address match lists are primarily used to determine access
 492             control for various server operations. They are also used in
 493             the <span><strong class="command">listen-on</strong></span> and <span><strong class="command">sortlist</strong></span>
 494             statements. The elements which constitute an address match
 495             list can be any of the following:
 496           </p>
 497 <div class="itemizedlist"><ul type="disc">
 498 <li>an IP address (IPv4 or IPv6)</li>
 499 <li>an IP prefix (in `/' notation)</li>
 500 <li>
 501                 a key ID, as defined by the <span><strong class="command">key</strong></span>
 502                 statement
 503               </li>
 504 <li>the name of an address match list defined with
 505                 the <span><strong class="command">acl</strong></span> statement
 506               </li>
 507 <li>a nested address match list enclosed in braces</li>
 508 </ul></div>
 509 <p>
 510             Elements can be negated with a leading exclamation mark (`!'),
 511             and the match list names "any", "none", "localhost", and
 512             "localnets" are predefined. More information on those names
 513             can be found in the description of the acl statement.
 514           </p>
 515 <p>
 516             The addition of the key clause made the name of this syntactic
 517             element something of a misnomer, since security keys can be used
 518             to validate access without regard to a host or network address.
 519             Nonetheless, the term "address match list" is still used
 520             throughout the documentation.
 521           </p>
 522 <p>
 523             When a given IP address or prefix is compared to an address
 524             match list, the comparison takes place in approximately O(1)
 525             time.  However, key comparisons require that the list of keys
 526             be traversed until a matching key is found, and therefore may
 527             be somewhat slower.
 528           </p>
 529 <p>
 530             The interpretation of a match depends on whether the list is being
 531             used for access control, defining <span><strong class="command">listen-on</strong></span> ports, or in a
 532             <span><strong class="command">sortlist</strong></span>, and whether the element was negated.
 533           </p>
 534 <p>
 535             When used as an access control list, a non-negated match
 536             allows access and a negated match denies access. If
 537             there is no match, access is denied. The clauses
 538             <span><strong class="command">allow-notify</strong></span>,
 539             <span><strong class="command">allow-recursion</strong></span>,
 540             <span><strong class="command">allow-recursion-on</strong></span>,
 541             <span><strong class="command">allow-query</strong></span>,
 542             <span><strong class="command">allow-query-on</strong></span>,
 543             <span><strong class="command">allow-query-cache</strong></span>,
 544             <span><strong class="command">allow-query-cache-on</strong></span>,
 545             <span><strong class="command">allow-transfer</strong></span>,
 546             <span><strong class="command">allow-update</strong></span>,
 547             <span><strong class="command">allow-update-forwarding</strong></span>, and
 548             <span><strong class="command">blackhole</strong></span> all use address match
 549             lists.  Similarly, the <span><strong class="command">listen-on</strong></span> option will cause the
 550             server to refuse queries on any of the machine's
 551             addresses which do not match the list.
 552           </p>
 553 <p>
 554             Order of insertion is significant.  If more than one element
 555             in an ACL is found to match a given IP address or prefix,
 556             preference will be given to the one that came
 557             <span class="emphasis"><em>first</em></span> in the ACL definition.
 558             Because of this first-match behavior, an element that
 559             defines a subset of another element in the list should
 560             come before the broader element, regardless of whether
 561             either is negated. For example, in
 562             <span><strong class="command">1.2.3/24; ! 1.2.3.13;</strong></span>
 563             the 1.2.3.13 element is completely useless because the
 564             algorithm will match any lookup for 1.2.3.13 to the 1.2.3/24
 565             element.  Using <span><strong class="command">! 1.2.3.13; 1.2.3/24</strong></span> fixes
 566             that problem by having 1.2.3.13 blocked by the negation, but
 567             all other 1.2.3.* hosts fall through.
 568           </p>
 569 </div>
 570 </div>
 571 <div class="sect2" lang="en">
 572 <div class="titlepage"><div><div><h3 class="title">
 573 <a name="id2573945"></a>Comment Syntax</h3></div></div></div>
 574 <p>
 575           The <acronym class="acronym">BIND</acronym> 9 comment syntax allows for
 576           comments to appear
 577           anywhere that whitespace may appear in a <acronym class="acronym">BIND</acronym> configuration
 578           file. To appeal to programmers of all kinds, they can be written
 579           in the C, C++, or shell/perl style.
 580         </p>
 581 <div class="sect3" lang="en">
 582 <div class="titlepage"><div><div><h4 class="title">
 583 <a name="id2573960"></a>Syntax</h4></div></div></div>
 584 <p>
 585             </p>
 586 <pre class="programlisting">/* This is a <acronym class="acronym">BIND</acronym> comment as in C */</pre>
 587 <p>
 588             </p>
 589 <pre class="programlisting">// This is a <acronym class="acronym">BIND</acronym> comment as in C++</pre>
 590 <p>
 591             </p>
 592 <pre class="programlisting"># This is a <acronym class="acronym">BIND</acronym> comment as in common UNIX shells
 593 # and perl</pre>
 594 <p>
 595           </p>
 596 </div>
 597 <div class="sect3" lang="en">
 598 <div class="titlepage"><div><div><h4 class="title">
 599 <a name="id2573990"></a>Definition and Usage</h4></div></div></div>
 600 <p>
 601             Comments may appear anywhere that whitespace may appear in
 602             a <acronym class="acronym">BIND</acronym> configuration file.
 603           </p>
 604 <p>
 605             C-style comments start with the two characters /* (slash,
 606             star) and end with */ (star, slash). Because they are completely
 607             delimited with these characters, they can be used to comment only
 608             a portion of a line or to span multiple lines.
 609           </p>
 610 <p>
 611             C-style comments cannot be nested. For example, the following
 612             is not valid because the entire comment ends with the first */:
 613           </p>
 614 <p>
 615
 616 </p>
 617 <pre class="programlisting">/* This is the start of a comment.
 618    This is still part of the comment.
 619 /* This is an incorrect attempt at nesting a comment. */
 620    This is no longer in any comment. */
 621 </pre>
 622 <p>
 623
 624           </p>
 625 <p>
 626             C++-style comments start with the two characters // (slash,
 627             slash) and continue to the end of the physical line. They cannot
 628             be continued across multiple physical lines; to have one logical
 629             comment span multiple lines, each line must use the // pair.
 630             For example:
 631           </p>
 632 <p>
 633
 634 </p>
 635 <pre class="programlisting">// This is the start of a comment.  The next line
 636 // is a new comment, even though it is logically
 637 // part of the previous comment.
 638 </pre>
 639 <p>
 640
 641           </p>
 642 <p>
 643             Shell-style (or perl-style, if you prefer) comments start
 644             with the character <code class="literal">#</code> (number sign)
 645             and continue to the end of the
 646             physical line, as in C++ comments.
 647             For example:
 648           </p>
 649 <p>
 650
 651 </p>
 652 <pre class="programlisting"># This is the start of a comment.  The next line
 653 # is a new comment, even though it is logically
 654 # part of the previous comment.
 655 </pre>
 656 <p>
 657
 658           </p>
 659 <div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
 660 <h3 class="title">Warning</h3>
 661 <p>
 662               You cannot use the semicolon (`;') character
 663               to start a comment such as you would in a zone file. The
 664               semicolon indicates the end of a configuration
 665               statement.
 666             </p>
 667 </div>
 668 </div>
 669 </div>
 670 </div>
 671 <div class="sect1" lang="en">
 672 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
 673 <a name="Configuration_File_Grammar"></a>Configuration File Grammar</h2></div></div></div>
 674 <p>
 675         A <acronym class="acronym">BIND</acronym> 9 configuration consists of
 676         statements and comments.
 677         Statements end with a semicolon. Statements and comments are the
 678         only elements that can appear without enclosing braces. Many
 679         statements contain a block of sub-statements, which are also
 680         terminated with a semicolon.
 681       </p>
 682 <p>
 683         The following statements are supported:
 684       </p>
 685 <div class="informaltable"><table border="1">
 686 <colgroup>
 687 <col>
 688 <col>
 689 </colgroup>
 690 <tbody>
 691 <tr>
 692 <td>
 693                 <p><span><strong class="command">acl</strong></span></p>
 694               </td>
 695 <td>
 696                 <p>
 697                   defines a named IP address
 698                   matching list, for access control and other uses.
 699                 </p>
 700               </td>
 701 </tr>
 702 <tr>
 703 <td>
 704                 <p><span><strong class="command">controls</strong></span></p>
 705               </td>
 706 <td>
 707                 <p>
 708                   declares control channels to be used
 709                   by the <span><strong class="command">rndc</strong></span> utility.
 710                 </p>
 711               </td>
 712 </tr>
 713 <tr>
 714 <td>
 715                 <p><span><strong class="command">include</strong></span></p>
 716               </td>
 717 <td>
 718                 <p>
 719                   includes a file.
 720                 </p>
 721               </td>
 722 </tr>
 723 <tr>
 724 <td>
 725                 <p><span><strong class="command">key</strong></span></p>
 726               </td>
 727 <td>
 728                 <p>
 729                   specifies key information for use in
 730                   authentication and authorization using TSIG.
 731                 </p>
 732               </td>
 733 </tr>
 734 <tr>
 735 <td>
 736                 <p><span><strong class="command">logging</strong></span></p>
 737               </td>
 738 <td>
 739                 <p>
 740                   specifies what the server logs, and where
 741                   the log messages are sent.
 742                 </p>
 743               </td>
 744 </tr>
 745 <tr>
 746 <td>
 747                 <p><span><strong class="command">lwres</strong></span></p>
 748               </td>
 749 <td>
 750                 <p>
 751                   configures <span><strong class="command">named</strong></span> to
 752                   also act as a light-weight resolver daemon (<span><strong class="command">lwresd</strong></span>).
 753                 </p>
 754               </td>
 755 </tr>
 756 <tr>
 757 <td>
 758                 <p><span><strong class="command">masters</strong></span></p>
 759               </td>
 760 <td>
 761                 <p>
 762                   defines a named masters list for
 763                   inclusion in stub and slave zone masters clauses.
 764                 </p>
 765               </td>
 766 </tr>
 767 <tr>
 768 <td>
 769                 <p><span><strong class="command">options</strong></span></p>
 770               </td>
 771 <td>
 772                 <p>
 773                   controls global server configuration
 774                   options and sets defaults for other statements.
 775                 </p>
 776               </td>
 777 </tr>
 778 <tr>
 779 <td>
 780                 <p><span><strong class="command">server</strong></span></p>
 781               </td>
 782 <td>
 783                 <p>
 784                   sets certain configuration options on
 785                   a per-server basis.
 786                 </p>
 787               </td>
 788 </tr>
 789 <tr>
 790 <td>
 791                 <p><span><strong class="command">statistics-channels</strong></span></p>
 792               </td>
 793 <td>
 794                 <p>
 795                   declares communication channels to get access to
 796                   <span><strong class="command">named</strong></span> statistics.
 797                 </p>
 798               </td>
 799 </tr>
 800 <tr>
 801 <td>
 802                 <p><span><strong class="command">trusted-keys</strong></span></p>
 803               </td>
 804 <td>
 805                 <p>
 806                   defines trusted DNSSEC keys.
 807                 </p>
 808               </td>
 809 </tr>
 810 <tr>
 811 <td>
 812                 <p><span><strong class="command">managed-keys</strong></span></p>
 813               </td>
 814 <td>
 815                 <p>
 816                   lists DNSSEC keys to be kept up to date
 817                   using RFC 5011 trust anchor maintenance.
 818                 </p>
 819               </td>
 820 </tr>
 821 <tr>
 822 <td>
 823                 <p><span><strong class="command">view</strong></span></p>
 824               </td>
 825 <td>
 826                 <p>
 827                   defines a view.
 828                 </p>
 829               </td>
 830 </tr>
 831 <tr>
 832 <td>
 833                 <p><span><strong class="command">zone</strong></span></p>
 834               </td>
 835 <td>
 836                 <p>
 837                   defines a zone.
 838                 </p>
 839               </td>
 840 </tr>
 841 </tbody>
 842 </table></div>
 843 <p>
 844         The <span><strong class="command">logging</strong></span> and
 845         <span><strong class="command">options</strong></span> statements may only occur once
 846         per
 847         configuration.
 848       </p>
 849 <div class="sect2" lang="en">
 850 <div class="titlepage"><div><div><h3 class="title">
 851 <a name="id2574531"></a><span><strong class="command">acl</strong></span> Statement Grammar</h3></div></div></div>
 852 <pre class="programlisting"><span><strong class="command">acl</strong></span> acl-name {
 853     address_match_list
 854 };
 855 </pre>
 856 </div>
 857 <div class="sect2" lang="en">
 858 <div class="titlepage"><div><div><h3 class="title">
 859 <a name="acl"></a><span><strong class="command">acl</strong></span> Statement Definition and
 860           Usage</h3></div></div></div>
 861 <p>
 862           The <span><strong class="command">acl</strong></span> statement assigns a symbolic
 863           name to an address match list. It gets its name from a primary
 864           use of address match lists: Access Control Lists (ACLs).
 865         </p>
 866 <p>
 867           Note that an address match list's name must be defined
 868           with <span><strong class="command">acl</strong></span> before it can be used
 869           elsewhere; no forward references are allowed.
 870         </p>
 871 <p>
 872           The following ACLs are built-in:
 873         </p>
 874 <div class="informaltable"><table border="1">
 875 <colgroup>
 876 <col>
 877 <col>
 878 </colgroup>
 879 <tbody>
 880 <tr>
 881 <td>
 882                   <p><span><strong class="command">any</strong></span></p>
 883                 </td>
 884 <td>
 885                   <p>
 886                     Matches all hosts.
 887                   </p>
 888                 </td>
 889 </tr>
 890 <tr>
 891 <td>
 892                   <p><span><strong class="command">none</strong></span></p>
 893                 </td>
 894 <td>
 895                   <p>
 896                     Matches no hosts.
 897                   </p>
 898                 </td>
 899 </tr>
 900 <tr>
 901 <td>
 902                   <p><span><strong class="command">localhost</strong></span></p>
 903                 </td>
 904 <td>
 905                   <p>
 906                     Matches the IPv4 and IPv6 addresses of all network
 907                     interfaces on the system.
 908                   </p>
 909                 </td>
 910 </tr>
 911 <tr>
 912 <td>
 913                   <p><span><strong class="command">localnets</strong></span></p>
 914                 </td>
 915 <td>
 916                   <p>
 917                     Matches any host on an IPv4 or IPv6 network
 918                     for which the system has an interface.
 919                     Some systems do not provide a way to determine the prefix
 920                     lengths of
 921                     local IPv6 addresses.
 922                     In such a case, <span><strong class="command">localnets</strong></span>
 923                     only matches the local
 924                     IPv6 addresses, just like <span><strong class="command">localhost</strong></span>.
 925                   </p>
 926                 </td>
 927 </tr>
 928 </tbody>
 929 </table></div>
 930 </div>
 931 <div class="sect2" lang="en">
 932 <div class="titlepage"><div><div><h3 class="title">
 933 <a name="id2574789"></a><span><strong class="command">controls</strong></span> Statement Grammar</h3></div></div></div>
 934 <pre class="programlisting"><span><strong class="command">controls</strong></span> {
 935    [ inet ( ip_addr | * ) [ port ip_port ]
 936                 allow { <em class="replaceable"><code> address_match_list </code></em> }
 937                 keys { <em class="replaceable"><code>key_list</code></em> }; ]
 938    [ inet ...; ]
 939    [ unix <em class="replaceable"><code>path</code></em> perm <em class="replaceable"><code>number</code></em> owner <em class="replaceable"><code>number</code></em> group <em class="replaceable"><code>number</code></em>
 940      keys { <em class="replaceable"><code>key_list</code></em> }; ]
 941    [ unix ...; ]
 942 };
 943 </pre>
 944 </div>
 945 <div class="sect2" lang="en">
 946 <div class="titlepage"><div><div><h3 class="title">
 947 <a name="controls_statement_definition_and_usage"></a><span><strong class="command">controls</strong></span> Statement Definition and
 948           Usage</h3></div></div></div>
 949 <p>
 950           The <span><strong class="command">controls</strong></span> statement declares control
 951           channels to be used by system administrators to control the
 952           operation of the name server. These control channels are
 953           used by the <span><strong class="command">rndc</strong></span> utility to send
 954           commands to and retrieve non-DNS results from a name server.
 955         </p>
 956 <p>
 957           An <span><strong class="command">inet</strong></span> control channel is a TCP socket
 958           listening at the specified <span><strong class="command">ip_port</strong></span> on the
 959           specified <span><strong class="command">ip_addr</strong></span>, which can be an IPv4 or IPv6
 960           address.  An <span><strong class="command">ip_addr</strong></span> of <code class="literal">*</code> (asterisk) is
 961           interpreted as the IPv4 wildcard address; connections will be
 962           accepted on any of the system's IPv4 addresses.
 963           To listen on the IPv6 wildcard address,
 964           use an <span><strong class="command">ip_addr</strong></span> of <code class="literal">::</code>.
 965           If you will only use <span><strong class="command">rndc</strong></span> on the local host,
 966           using the loopback address (<code class="literal">127.0.0.1</code>
 967           or <code class="literal">::1</code>) is recommended for maximum security.
 968         </p>
 969 <p>
 970           If no port is specified, port 953 is used. The asterisk
 971           "<code class="literal">*</code>" cannot be used for <span><strong class="command">ip_port</strong></span>.
 972         </p>
 973 <p>
 974           The ability to issue commands over the control channel is
 975           restricted by the <span><strong class="command">allow</strong></span> and
 976           <span><strong class="command">keys</strong></span> clauses.
 977           Connections to the control channel are permitted based on the
 978           <span><strong class="command">address_match_list</strong></span>.  This is for simple
 979           IP address based filtering only; any <span><strong class="command">key_id</strong></span>
 980           elements of the <span><strong class="command">address_match_list</strong></span>
 981           are ignored.
 982         </p>
 983 <p>
 984           A <span><strong class="command">unix</strong></span> control channel is a UNIX domain
 985           socket listening at the specified path in the file system.
 986           Access to the socket is specified by the <span><strong class="command">perm</strong></span>,
 987           <span><strong class="command">owner</strong></span> and <span><strong class="command">group</strong></span> clauses.
 988           Note on some platforms (SunOS and Solaris) the permissions
 989           (<span><strong class="command">perm</strong></span>) are applied to the parent directory
 990           as the permissions on the socket itself are ignored.
 991         </p>
 992 <p>
 993           The primary authorization mechanism of the command
 994           channel is the <span><strong class="command">key_list</strong></span>, which
 995           contains a list of <span><strong class="command">key_id</strong></span>s.
 996           Each <span><strong class="command">key_id</strong></span> in the <span><strong class="command">key_list</strong></span>
 997           is authorized to execute commands over the control channel.
 998           See <a href="Bv9ARM.ch03.html#rndc">Remote Name Daemon Control application</a> in <a href="Bv9ARM.ch03.html#admin_tools" title="Administrative Tools">the section called &#8220;Administrative Tools&#8221;</a>)
 999           for information about configuring keys in <span><strong class="command">rndc</strong></span>.
1000         </p>
1001 <p>
1002           If no <span><strong class="command">controls</strong></span> statement is present,
1003           <span><strong class="command">named</strong></span> will set up a default
1004           control channel listening on the loopback address 127.0.0.1
1005           and its IPv6 counterpart ::1.
1006           In this case, and also when the <span><strong class="command">controls</strong></span> statement
1007           is present but does not have a <span><strong class="command">keys</strong></span> clause,
1008           <span><strong class="command">named</strong></span> will attempt to load the command channel key
1009           from the file <code class="filename">rndc.key</code> in
1010           <code class="filename">/etc</code> (or whatever <code class="varname">sysconfdir</code>
1011           was specified as when <acronym class="acronym">BIND</acronym> was built).
1012           To create a <code class="filename">rndc.key</code> file, run
1013           <strong class="userinput"><code>rndc-confgen -a</code></strong>.
1014         </p>
1015 <p>
1016           The <code class="filename">rndc.key</code> feature was created to
1017           ease the transition of systems from <acronym class="acronym">BIND</acronym> 8,
1018           which did not have digital signatures on its command channel
1019           messages and thus did not have a <span><strong class="command">keys</strong></span> clause.
1020
1021           It makes it possible to use an existing <acronym class="acronym">BIND</acronym> 8
1022           configuration file in <acronym class="acronym">BIND</acronym> 9 unchanged,
1023           and still have <span><strong class="command">rndc</strong></span> work the same way
1024           <span><strong class="command">ndc</strong></span> worked in BIND 8, simply by executing the
1025           command <strong class="userinput"><code>rndc-confgen -a</code></strong> after BIND 9 is
1026           installed.
1027         </p>
1028 <p>
1029           Since the <code class="filename">rndc.key</code> feature
1030           is only intended to allow the backward-compatible usage of
1031           <acronym class="acronym">BIND</acronym> 8 configuration files, this
1032           feature does not
1033           have a high degree of configurability.  You cannot easily change
1034           the key name or the size of the secret, so you should make a
1035           <code class="filename">rndc.conf</code> with your own key if you
1036           wish to change
1037           those things.  The <code class="filename">rndc.key</code> file
1038           also has its
1039           permissions set such that only the owner of the file (the user that
1040           <span><strong class="command">named</strong></span> is running as) can access it.
1041           If you
1042           desire greater flexibility in allowing other users to access
1043           <span><strong class="command">rndc</strong></span> commands, then you need to create
1044           a
1045           <code class="filename">rndc.conf</code> file and make it group
1046           readable by a group
1047           that contains the users who should have access.
1048         </p>
1049 <p>
1050           To disable the command channel, use an empty
1051           <span><strong class="command">controls</strong></span> statement:
1052           <span><strong class="command">controls { };</strong></span>.
1053         </p>
1054 </div>
1055 <div class="sect2" lang="en">
1056 <div class="titlepage"><div><div><h3 class="title">
1057 <a name="id2575148"></a><span><strong class="command">include</strong></span> Statement Grammar</h3></div></div></div>
1058 <pre class="programlisting"><span><strong class="command">include</strong></span> <em class="replaceable"><code>filename</code></em>;</pre>
1059 </div>
1060 <div class="sect2" lang="en">
1061 <div class="titlepage"><div><div><h3 class="title">
1062 <a name="id2575165"></a><span><strong class="command">include</strong></span> Statement Definition and
1063           Usage</h3></div></div></div>
1064 <p>
1065           The <span><strong class="command">include</strong></span> statement inserts the
1066           specified file at the point where the <span><strong class="command">include</strong></span>
1067           statement is encountered. The <span><strong class="command">include</strong></span>
1068                 statement facilitates the administration of configuration
1069           files
1070           by permitting the reading or writing of some things but not
1071           others. For example, the statement could include private keys
1072           that are readable only by the name server.
1073         </p>
1074 </div>
1075 <div class="sect2" lang="en">
1076 <div class="titlepage"><div><div><h3 class="title">
1077 <a name="id2575189"></a><span><strong class="command">key</strong></span> Statement Grammar</h3></div></div></div>
1078 <pre class="programlisting"><span><strong class="command">key</strong></span> <em class="replaceable"><code>key_id</code></em> {
1079     algorithm <em class="replaceable"><code>string</code></em>;
1080     secret <em class="replaceable"><code>string</code></em>;
1081 };
1082 </pre>
1083 </div>
1084 <div class="sect2" lang="en">
1085 <div class="titlepage"><div><div><h3 class="title">
1086 <a name="id2575212"></a><span><strong class="command">key</strong></span> Statement Definition and Usage</h3></div></div></div>
1087 <p>
1088           The <span><strong class="command">key</strong></span> statement defines a shared
1089           secret key for use with TSIG (see <a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
1090           or the command channel
1091           (see <a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and
1092           Usage">the section called &#8220;<span><strong class="command">controls</strong></span> Statement Definition and
1093           Usage&#8221;</a>).
1094         </p>
1095 <p>
1096           The <span><strong class="command">key</strong></span> statement can occur at the
1097           top level
1098           of the configuration file or inside a <span><strong class="command">view</strong></span>
1099           statement.  Keys defined in top-level <span><strong class="command">key</strong></span>
1100           statements can be used in all views.  Keys intended for use in
1101           a <span><strong class="command">controls</strong></span> statement
1102           (see <a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and
1103           Usage">the section called &#8220;<span><strong class="command">controls</strong></span> Statement Definition and
1104           Usage&#8221;</a>)
1105           must be defined at the top level.
1106         </p>
1107 <p>
1108           The <em class="replaceable"><code>key_id</code></em>, also known as the
1109           key name, is a domain name uniquely identifying the key. It can
1110           be used in a <span><strong class="command">server</strong></span>
1111           statement to cause requests sent to that
1112           server to be signed with this key, or in address match lists to
1113           verify that incoming requests have been signed with a key
1114           matching this name, algorithm, and secret.
1115         </p>
1116 <p>
1117           The <em class="replaceable"><code>algorithm_id</code></em> is a string
1118           that specifies a security/authentication algorithm.  Named
1119           supports <code class="literal">hmac-md5</code>,
1120           <code class="literal">hmac-sha1</code>, <code class="literal">hmac-sha224</code>,
1121           <code class="literal">hmac-sha256</code>, <code class="literal">hmac-sha384</code>
1122           and <code class="literal">hmac-sha512</code> TSIG authentication.
1123           Truncated hashes are supported by appending the minimum
1124           number of required bits preceded by a dash, e.g.
1125           <code class="literal">hmac-sha1-80</code>.  The
1126           <em class="replaceable"><code>secret_string</code></em> is the secret
1127           to be used by the algorithm, and is treated as a base-64
1128           encoded string.
1129         </p>
1130 </div>
1131 <div class="sect2" lang="en">
1132 <div class="titlepage"><div><div><h3 class="title">
1133 <a name="id2575303"></a><span><strong class="command">logging</strong></span> Statement Grammar</h3></div></div></div>
1134 <pre class="programlisting"><span><strong class="command">logging</strong></span> {
1135    [ <span><strong class="command">channel</strong></span> <em class="replaceable"><code>channel_name</code></em> {
1136      ( <span><strong class="command">file</strong></span> <em class="replaceable"><code>path_name</code></em>
1137          [ <span><strong class="command">versions</strong></span> ( <em class="replaceable"><code>number</code></em> | <span><strong class="command">unlimited</strong></span> ) ]
1138          [ <span><strong class="command">size</strong></span> <em class="replaceable"><code>size spec</code></em> ]
1139        | <span><strong class="command">syslog</strong></span> <em class="replaceable"><code>syslog_facility</code></em>
1140        | <span><strong class="command">stderr</strong></span>
1141        | <span><strong class="command">null</strong></span> );
1142      [ <span><strong class="command">severity</strong></span> (<code class="option">critical</code> | <code class="option">error</code> | <code class="option">warning</code> | <code class="option">notice</code> |
1143                  <code class="option">info</code> | <code class="option">debug</code> [ <em class="replaceable"><code>level</code></em> ] | <code class="option">dynamic</code> ); ]
1144      [ <span><strong class="command">print-category</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1145      [ <span><strong class="command">print-severity</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1146      [ <span><strong class="command">print-time</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1147    }; ]
1148    [ <span><strong class="command">category</strong></span> <em class="replaceable"><code>category_name</code></em> {
1149      <em class="replaceable"><code>channel_name</code></em> ; [ <em class="replaceable"><code>channel_name</code></em> ; ... ]
1150    }; ]
1151    ...
1152 };
1153 </pre>
1154 </div>
1155 <div class="sect2" lang="en">
1156 <div class="titlepage"><div><div><h3 class="title">
1157 <a name="id2575429"></a><span><strong class="command">logging</strong></span> Statement Definition and
1158           Usage</h3></div></div></div>
1159 <p>
1160           The <span><strong class="command">logging</strong></span> statement configures a
1161           wide
1162           variety of logging options for the name server. Its <span><strong class="command">channel</strong></span> phrase
1163           associates output methods, format options and severity levels with
1164           a name that can then be used with the <span><strong class="command">category</strong></span> phrase
1165           to select how various classes of messages are logged.
1166         </p>
1167 <p>
1168           Only one <span><strong class="command">logging</strong></span> statement is used to
1169           define
1170           as many channels and categories as are wanted. If there is no <span><strong class="command">logging</strong></span> statement,
1171           the logging configuration will be:
1172         </p>
1173 <pre class="programlisting">logging {
1174      category default { default_syslog; default_debug; };
1175      category unmatched { null; };
1176 };
1177 </pre>
1178 <p>
1179           In <acronym class="acronym">BIND</acronym> 9, the logging configuration
1180           is only established when
1181           the entire configuration file has been parsed.  In <acronym class="acronym">BIND</acronym> 8, it was
1182           established as soon as the <span><strong class="command">logging</strong></span>
1183           statement
1184           was parsed. When the server is starting up, all logging messages
1185           regarding syntax errors in the configuration file go to the default
1186           channels, or to standard error if the "<code class="option">-g</code>" option
1187           was specified.
1188         </p>
1189 <div class="sect3" lang="en">
1190 <div class="titlepage"><div><div><h4 class="title">
1191 <a name="id2575481"></a>The <span><strong class="command">channel</strong></span> Phrase</h4></div></div></div>
1192 <p>
1193             All log output goes to one or more <span class="emphasis"><em>channels</em></span>;
1194             you can make as many of them as you want.
1195           </p>
1196 <p>
1197             Every channel definition must include a destination clause that
1198             says whether messages selected for the channel go to a file, to a
1199             particular syslog facility, to the standard error stream, or are
1200             discarded. It can optionally also limit the message severity level
1201             that will be accepted by the channel (the default is
1202             <span><strong class="command">info</strong></span>), and whether to include a
1203             <span><strong class="command">named</strong></span>-generated time stamp, the
1204             category name
1205             and/or severity level (the default is not to include any).
1206           </p>
1207 <p>
1208             The <span><strong class="command">null</strong></span> destination clause
1209             causes all messages sent to the channel to be discarded;
1210             in that case, other options for the channel are meaningless.
1211           </p>
1212 <p>
1213             The <span><strong class="command">file</strong></span> destination clause directs
1214             the channel
1215             to a disk file.  It can include limitations
1216             both on how large the file is allowed to become, and how many
1217             versions
1218             of the file will be saved each time the file is opened.
1219           </p>
1220 <p>
1221             If you use the <span><strong class="command">versions</strong></span> log file
1222             option, then
1223             <span><strong class="command">named</strong></span> will retain that many backup
1224             versions of the file by
1225             renaming them when opening.  For example, if you choose to keep
1226             three old versions
1227             of the file <code class="filename">lamers.log</code>, then just
1228             before it is opened
1229             <code class="filename">lamers.log.1</code> is renamed to
1230             <code class="filename">lamers.log.2</code>, <code class="filename">lamers.log.0</code> is renamed
1231             to <code class="filename">lamers.log.1</code>, and <code class="filename">lamers.log</code> is
1232             renamed to <code class="filename">lamers.log.0</code>.
1233             You can say <span><strong class="command">versions unlimited</strong></span> to
1234             not limit
1235             the number of versions.
1236             If a <span><strong class="command">size</strong></span> option is associated with
1237             the log file,
1238             then renaming is only done when the file being opened exceeds the
1239             indicated size.  No backup versions are kept by default; any
1240             existing
1241             log file is simply appended.
1242           </p>
1243 <p>
1244             The <span><strong class="command">size</strong></span> option for files is used
1245             to limit log
1246             growth. If the file ever exceeds the size, then <span><strong class="command">named</strong></span> will
1247             stop writing to the file unless it has a <span><strong class="command">versions</strong></span> option
1248             associated with it.  If backup versions are kept, the files are
1249             rolled as
1250             described above and a new one begun.  If there is no
1251             <span><strong class="command">versions</strong></span> option, no more data will
1252             be written to the log
1253             until some out-of-band mechanism removes or truncates the log to
1254             less than the
1255             maximum size.  The default behavior is not to limit the size of
1256             the
1257             file.
1258           </p>
1259 <p>
1260             Example usage of the <span><strong class="command">size</strong></span> and
1261             <span><strong class="command">versions</strong></span> options:
1262           </p>
1263 <pre class="programlisting">channel an_example_channel {
1264     file "example.log" versions 3 size 20m;
1265     print-time yes;
1266     print-category yes;
1267 };
1268 </pre>
1269 <p>
1270             The <span><strong class="command">syslog</strong></span> destination clause
1271             directs the
1272             channel to the system log.  Its argument is a
1273             syslog facility as described in the <span><strong class="command">syslog</strong></span> man
1274             page. Known facilities are <span><strong class="command">kern</strong></span>, <span><strong class="command">user</strong></span>,
1275             <span><strong class="command">mail</strong></span>, <span><strong class="command">daemon</strong></span>, <span><strong class="command">auth</strong></span>,
1276             <span><strong class="command">syslog</strong></span>, <span><strong class="command">lpr</strong></span>, <span><strong class="command">news</strong></span>,
1277             <span><strong class="command">uucp</strong></span>, <span><strong class="command">cron</strong></span>, <span><strong class="command">authpriv</strong></span>,
1278             <span><strong class="command">ftp</strong></span>, <span><strong class="command">local0</strong></span>, <span><strong class="command">local1</strong></span>,
1279             <span><strong class="command">local2</strong></span>, <span><strong class="command">local3</strong></span>, <span><strong class="command">local4</strong></span>,
1280             <span><strong class="command">local5</strong></span>, <span><strong class="command">local6</strong></span> and
1281             <span><strong class="command">local7</strong></span>, however not all facilities
1282             are supported on
1283             all operating systems.
1284             How <span><strong class="command">syslog</strong></span> will handle messages
1285             sent to
1286             this facility is described in the <span><strong class="command">syslog.conf</strong></span> man
1287             page. If you have a system which uses a very old version of <span><strong class="command">syslog</strong></span> that
1288             only uses two arguments to the <span><strong class="command">openlog()</strong></span> function,
1289             then this clause is silently ignored.
1290           </p>
1291 <p>
1292             The <span><strong class="command">severity</strong></span> clause works like <span><strong class="command">syslog</strong></span>'s
1293             "priorities", except that they can also be used if you are writing
1294             straight to a file rather than using <span><strong class="command">syslog</strong></span>.
1295             Messages which are not at least of the severity level given will
1296             not be selected for the channel; messages of higher severity
1297             levels
1298             will be accepted.
1299           </p>
1300 <p>
1301             If you are using <span><strong class="command">syslog</strong></span>, then the <span><strong class="command">syslog.conf</strong></span> priorities
1302             will also determine what eventually passes through. For example,
1303             defining a channel facility and severity as <span><strong class="command">daemon</strong></span> and <span><strong class="command">debug</strong></span> but
1304             only logging <span><strong class="command">daemon.warning</strong></span> via <span><strong class="command">syslog.conf</strong></span> will
1305             cause messages of severity <span><strong class="command">info</strong></span> and
1306             <span><strong class="command">notice</strong></span> to
1307             be dropped. If the situation were reversed, with <span><strong class="command">named</strong></span> writing
1308             messages of only <span><strong class="command">warning</strong></span> or higher,
1309             then <span><strong class="command">syslogd</strong></span> would
1310             print all messages it received from the channel.
1311           </p>
1312 <p>
1313             The <span><strong class="command">stderr</strong></span> destination clause
1314             directs the
1315             channel to the server's standard error stream.  This is intended
1316             for
1317             use when the server is running as a foreground process, for
1318             example
1319             when debugging a configuration.
1320           </p>
1321 <p>
1322             The server can supply extensive debugging information when
1323             it is in debugging mode. If the server's global debug level is
1324             greater
1325             than zero, then debugging mode will be active. The global debug
1326             level is set either by starting the <span><strong class="command">named</strong></span> server
1327             with the <code class="option">-d</code> flag followed by a positive integer,
1328             or by running <span><strong class="command">rndc trace</strong></span>.
1329             The global debug level
1330             can be set to zero, and debugging mode turned off, by running <span><strong class="command">rndc
1331 notrace</strong></span>. All debugging messages in the server have a debug
1332             level, and higher debug levels give more detailed output. Channels
1333             that specify a specific debug severity, for example:
1334           </p>
1335 <pre class="programlisting">channel specific_debug_level {
1336     file "foo";
1337     severity debug 3;
1338 };
1339 </pre>
1340 <p>
1341             will get debugging output of level 3 or less any time the
1342             server is in debugging mode, regardless of the global debugging
1343             level. Channels with <span><strong class="command">dynamic</strong></span>
1344             severity use the
1345             server's global debug level to determine what messages to print.
1346           </p>
1347 <p>
1348             If <span><strong class="command">print-time</strong></span> has been turned on,
1349             then
1350             the date and time will be logged. <span><strong class="command">print-time</strong></span> may
1351             be specified for a <span><strong class="command">syslog</strong></span> channel,
1352             but is usually
1353             pointless since <span><strong class="command">syslog</strong></span> also logs
1354             the date and
1355             time. If <span><strong class="command">print-category</strong></span> is
1356             requested, then the
1357             category of the message will be logged as well. Finally, if <span><strong class="command">print-severity</strong></span> is
1358             on, then the severity level of the message will be logged. The <span><strong class="command">print-</strong></span> options may
1359             be used in any combination, and will always be printed in the
1360             following
1361             order: time, category, severity. Here is an example where all
1362             three <span><strong class="command">print-</strong></span> options
1363             are on:
1364           </p>
1365 <p>
1366             <code class="computeroutput">28-Feb-2000 15:05:32.863 general: notice: running</code>
1367           </p>
1368 <p>
1369             There are four predefined channels that are used for
1370             <span><strong class="command">named</strong></span>'s default logging as follows.
1371             How they are
1372             used is described in <a href="Bv9ARM.ch06.html#the_category_phrase" title="The category Phrase">the section called &#8220;The <span><strong class="command">category</strong></span> Phrase&#8221;</a>.
1373           </p>
1374 <pre class="programlisting">channel default_syslog {
1375     // send to syslog's daemon facility
1376     syslog daemon;
1377     // only send priority info and higher
1378     severity info;
1379
1380 channel default_debug {
1381     // write to named.run in the working directory
1382     // Note: stderr is used instead of "named.run" if
1383     // the server is started with the '-f' option.
1384     file "named.run";
1385     // log at the server's current debug level
1386     severity dynamic;
1387 };
1388
1389 channel default_stderr {
1390     // writes to stderr
1391     stderr;
1392     // only send priority info and higher
1393     severity info;
1394 };
1395
1396 channel null {
1397    // toss anything sent to this channel
1398    null;
1399 };
1400 </pre>
1401 <p>
1402             The <span><strong class="command">default_debug</strong></span> channel has the
1403             special
1404             property that it only produces output when the server's debug
1405             level is
1406             nonzero.  It normally writes to a file called <code class="filename">named.run</code>
1407             in the server's working directory.
1408           </p>
1409 <p>
1410             For security reasons, when the "<code class="option">-u</code>"
1411             command line option is used, the <code class="filename">named.run</code> file
1412             is created only after <span><strong class="command">named</strong></span> has
1413             changed to the
1414             new UID, and any debug output generated while <span><strong class="command">named</strong></span> is
1415             starting up and still running as root is discarded.  If you need
1416             to capture this output, you must run the server with the "<code class="option">-g</code>"
1417             option and redirect standard error to a file.
1418           </p>
1419 <p>
1420             Once a channel is defined, it cannot be redefined. Thus you
1421             cannot alter the built-in channels directly, but you can modify
1422             the default logging by pointing categories at channels you have
1423             defined.
1424           </p>
1425 </div>
1426 <div class="sect3" lang="en">
1427 <div class="titlepage"><div><div><h4 class="title">
1428 <a name="the_category_phrase"></a>The <span><strong class="command">category</strong></span> Phrase</h4></div></div></div>
1429 <p>
1430             There are many categories, so you can send the logs you want
1431             to see wherever you want, without seeing logs you don't want. If
1432             you don't specify a list of channels for a category, then log
1433             messages
1434             in that category will be sent to the <span><strong class="command">default</strong></span> category
1435             instead. If you don't specify a default category, the following
1436             "default default" is used:
1437           </p>
1438 <pre class="programlisting">category default { default_syslog; default_debug; };
1439 </pre>
1440 <p>
1441             As an example, let's say you want to log security events to
1442             a file, but you also want keep the default logging behavior. You'd
1443             specify the following:
1444           </p>
1445 <pre class="programlisting">channel my_security_channel {
1446     file "my_security_file";
1447     severity info;
1448 };
1449 category security {
1450     my_security_channel;
1451     default_syslog;
1452     default_debug;
1453 };</pre>
1454 <p>
1455             To discard all messages in a category, specify the <span><strong class="command">null</strong></span> channel:
1456           </p>
1457 <pre class="programlisting">category xfer-out { null; };
1458 category notify { null; };
1459 </pre>
1460 <p>
1461             Following are the available categories and brief descriptions
1462             of the types of log information they contain. More
1463             categories may be added in future <acronym class="acronym">BIND</acronym> releases.
1464           </p>
1465 <div class="informaltable"><table border="1">
1466 <colgroup>
1467 <col>
1468 <col>
1469 </colgroup>
1470 <tbody>
1471 <tr>
1472 <td>
1473                     <p><span><strong class="command">default</strong></span></p>
1474                   </td>
1475 <td>
1476                     <p>
1477                       The default category defines the logging
1478                       options for those categories where no specific
1479                       configuration has been
1480                       defined.
1481                     </p>
1482                   </td>
1483 </tr>
1484 <tr>
1485 <td>
1486                     <p><span><strong class="command">general</strong></span></p>
1487                   </td>
1488 <td>
1489                     <p>
1490                       The catch-all. Many things still aren't
1491                       classified into categories, and they all end up here.
1492                     </p>
1493                   </td>
1494 </tr>
1495 <tr>
1496 <td>
1497                     <p><span><strong class="command">database</strong></span></p>
1498                   </td>
1499 <td>
1500                     <p>
1501                       Messages relating to the databases used
1502                       internally by the name server to store zone and cache
1503                       data.
1504                     </p>
1505                   </td>
1506 </tr>
1507 <tr>
1508 <td>
1509                     <p><span><strong class="command">security</strong></span></p>
1510                   </td>
1511 <td>
1512                     <p>
1513                       Approval and denial of requests.
1514                     </p>
1515                   </td>
1516 </tr>
1517 <tr>
1518 <td>
1519                     <p><span><strong class="command">config</strong></span></p>
1520                   </td>
1521 <td>
1522                     <p>
1523                       Configuration file parsing and processing.
1524                     </p>
1525                   </td>
1526 </tr>
1527 <tr>
1528 <td>
1529                     <p><span><strong class="command">resolver</strong></span></p>
1530                   </td>
1531 <td>
1532                     <p>
1533                       DNS resolution, such as the recursive
1534                       lookups performed on behalf of clients by a caching name
1535                       server.
1536                     </p>
1537                   </td>
1538 </tr>
1539 <tr>
1540 <td>
1541                     <p><span><strong class="command">xfer-in</strong></span></p>
1542                   </td>
1543 <td>
1544                     <p>
1545                       Zone transfers the server is receiving.
1546                     </p>
1547                   </td>
1548 </tr>
1549 <tr>
1550 <td>
1551                     <p><span><strong class="command">xfer-out</strong></span></p>
1552                   </td>
1553 <td>
1554                     <p>
1555                       Zone transfers the server is sending.
1556                     </p>
1557                   </td>
1558 </tr>
1559 <tr>
1560 <td>
1561                     <p><span><strong class="command">notify</strong></span></p>
1562                   </td>
1563 <td>
1564                     <p>
1565                       The NOTIFY protocol.
1566                     </p>
1567                   </td>
1568 </tr>
1569 <tr>
1570 <td>
1571                     <p><span><strong class="command">client</strong></span></p>
1572                   </td>
1573 <td>
1574                     <p>
1575                       Processing of client requests.
1576                     </p>
1577                   </td>
1578 </tr>
1579 <tr>
1580 <td>
1581                     <p><span><strong class="command">unmatched</strong></span></p>
1582                   </td>
1583 <td>
1584                     <p>
1585                       Messages that <span><strong class="command">named</strong></span> was unable to determine the
1586                       class of or for which there was no matching <span><strong class="command">view</strong></span>.
1587                       A one line summary is also logged to the <span><strong class="command">client</strong></span> category.
1588                       This category is best sent to a file or stderr, by
1589                       default it is sent to
1590                       the <span><strong class="command">null</strong></span> channel.
1591                     </p>
1592                   </td>
1593 </tr>
1594 <tr>
1595 <td>
1596                     <p><span><strong class="command">network</strong></span></p>
1597                   </td>
1598 <td>
1599                     <p>
1600                       Network operations.
1601                     </p>
1602                   </td>
1603 </tr>
1604 <tr>
1605 <td>
1606                     <p><span><strong class="command">update</strong></span></p>
1607                   </td>
1608 <td>
1609                     <p>
1610                       Dynamic updates.
1611                     </p>
1612                   </td>
1613 </tr>
1614 <tr>
1615 <td>
1616                     <p><span><strong class="command">update-security</strong></span></p>
1617                   </td>
1618 <td>
1619                     <p>
1620                       Approval and denial of update requests.
1621                     </p>
1622                   </td>
1623 </tr>
1624 <tr>
1625 <td>
1626                     <p><span><strong class="command">queries</strong></span></p>
1627                   </td>
1628 <td>
1629                     <p>
1630                       Specify where queries should be logged to.
1631                     </p>
1632                     <p>
1633                       At startup, specifying the category <span><strong class="command">queries</strong></span> will also
1634                       enable query logging unless <span><strong class="command">querylog</strong></span> option has been
1635                       specified.
1636                     </p>
1637
1638                     <p>
1639                       The query log entry reports the client's IP
1640                       address and port number, and the query name,
1641                       class and type.  Next it reports whether the
1642                       Recursion Desired flag was set (+ if set, -
1643                       if not set), if the query was signed (S),
1644                       EDNS was in use (E), if TCP was used (T), if
1645                       DO (DNSSEC Ok) was set (D), or if CD (Checking
1646                       Disabled) was set (C).  After this the
1647                       destination address the query was sent to is
1648                       reported.
1649                     </p>
1650
1651                     <p>
1652                       <code class="computeroutput">client 127.0.0.1#62536: query: www.example.com IN AAAA +SE</code>
1653                     </p>
1654                     <p>
1655                       <code class="computeroutput">client ::1#62537: query: www.example.net IN AAAA -SE</code>
1656                     </p>
1657                   </td>
1658 </tr>
1659 <tr>
1660 <td>
1661                     <p><span><strong class="command">query-errors</strong></span></p>
1662                   </td>
1663 <td>
1664                     <p>
1665                       Information about queries that resulted in some
1666                       failure.
1667                     </p>
1668                   </td>
1669 </tr>
1670 <tr>
1671 <td>
1672                     <p><span><strong class="command">dispatch</strong></span></p>
1673                   </td>
1674 <td>
1675                     <p>
1676                       Dispatching of incoming packets to the
1677                       server modules where they are to be processed.
1678                     </p>
1679                   </td>
1680 </tr>
1681 <tr>
1682 <td>
1683                     <p><span><strong class="command">dnssec</strong></span></p>
1684                   </td>
1685 <td>
1686                     <p>
1687                       DNSSEC and TSIG protocol processing.
1688                     </p>
1689                   </td>
1690 </tr>
1691 <tr>
1692 <td>
1693                     <p><span><strong class="command">lame-servers</strong></span></p>
1694                   </td>
1695 <td>
1696                     <p>
1697                       Lame servers.  These are misconfigurations
1698                       in remote servers, discovered by BIND 9 when trying to
1699                       query those servers during resolution.
1700                     </p>
1701                   </td>
1702 </tr>
1703 <tr>
1704 <td>
1705                     <p><span><strong class="command">delegation-only</strong></span></p>
1706                   </td>
1707 <td>
1708                     <p>
1709                       Delegation only.  Logs queries that have been
1710                       forced to NXDOMAIN as the result of a
1711                       delegation-only zone or a
1712                       <span><strong class="command">delegation-only</strong></span> in a hint
1713                       or stub zone declaration.
1714                     </p>
1715                   </td>
1716 </tr>
1717 <tr>
1718 <td>
1719                     <p><span><strong class="command">edns-disabled</strong></span></p>
1720                   </td>
1721 <td>
1722                     <p>
1723                       Log queries that have been forced to use plain
1724                       DNS due to timeouts.  This is often due to
1725                       the remote servers not being RFC 1034 compliant
1726                       (not always returning FORMERR or similar to
1727                       EDNS queries and other extensions to the DNS
1728                       when they are not understood).  In other words, this is
1729                       targeted at servers that fail to respond to
1730                       DNS queries that they don't understand.
1731                     </p>
1732                     <p>
1733                       Note: the log message can also be due to
1734                       packet loss.  Before reporting servers for
1735                       non-RFC 1034 compliance they should be re-tested
1736                       to determine the nature of the non-compliance.
1737                       This testing should prevent or reduce the
1738                       number of false-positive reports.
1739                     </p>
1740                     <p>
1741                       Note: eventually <span><strong class="command">named</strong></span> will have to stop
1742                       treating such timeouts as due to RFC 1034 non
1743                       compliance and start treating it as plain
1744                       packet loss.  Falsely classifying packet
1745                       loss as due to RFC 1034 non compliance impacts
1746                       on DNSSEC validation which requires EDNS for
1747                       the DNSSEC records to be returned.
1748                     </p>
1749                   </td>
1750 </tr>
1751 </tbody>
1752 </table></div>
1753 </div>
1754 <div class="sect3" lang="en">
1755 <div class="titlepage"><div><div><h4 class="title">
1756 <a name="id2576977"></a>The <span><strong class="command">query-errors</strong></span> Category</h4></div></div></div>
1757 <p>
1758             The <span><strong class="command">query-errors</strong></span> category is
1759             specifically intended for debugging purposes: To identify
1760             why and how specific queries result in responses which
1761             indicate an error.
1762             Messages of this category are therefore only logged
1763             with <span><strong class="command">debug</strong></span> levels.
1764           </p>
1765 <p>
1766             At the debug levels of 1 or higher, each response with the
1767             rcode of SERVFAIL is logged as follows:
1768           </p>
1769 <p>
1770             <code class="computeroutput">client 127.0.0.1#61502: query failed (SERVFAIL) for www.example.com/IN/AAAA at query.c:3880</code>
1771           </p>
1772 <p>
1773             This means an error resulting in SERVFAIL was
1774             detected at line 3880 of source file
1775             <code class="filename">query.c</code>.
1776             Log messages of this level will particularly
1777             help identify the cause of SERVFAIL for an
1778             authoritative server.
1779           </p>
1780 <p>
1781             At the debug levels of 2 or higher, detailed context
1782             information of recursive resolutions that resulted in
1783             SERVFAIL is logged.
1784             The log message will look like as follows:
1785           </p>
1786 <p>
1787
1788             </p>
1789 <pre class="programlisting">
1790 fetch completed at resolver.c:2970 for www.example.com/A
1791 in 30.000183: timed out/success [domain:example.com,
1792 referral:2,restart:7,qrysent:8,timeout:5,lame:0,neterr:0,
1793 badresp:1,adberr:0,findfail:0,valfail:0]
1794             </pre>
1795 <p>
1796           </p>
1797 <p>
1798             The first part before the colon shows that a recursive
1799             resolution for AAAA records of www.example.com completed
1800             in 30.000183 seconds and the final result that led to the
1801             SERVFAIL was determined at line 2970 of source file
1802             <code class="filename">resolver.c</code>.
1803           </p>
1804 <p>
1805             The following part shows the detected final result and the
1806             latest result of DNSSEC validation.
1807             The latter is always success when no validation attempt
1808             is made.
1809             In this example, this query resulted in SERVFAIL probably
1810             because all name servers are down or unreachable, leading
1811             to a timeout in 30 seconds.
1812             DNSSEC validation was probably not attempted.
1813           </p>
1814 <p>
1815             The last part enclosed in square brackets shows statistics
1816             information collected for this particular resolution
1817             attempt.
1818             The <code class="varname">domain</code> field shows the deepest zone
1819             that the resolver reached;
1820             it is the zone where the error was finally detected.
1821             The meaning of the other fields is summarized in the
1822             following table.
1823           </p>
1824 <div class="informaltable"><table border="1">
1825 <colgroup>
1826 <col>
1827 <col>
1828 </colgroup>
1829 <tbody>
1830 <tr>
1831 <td>
1832                     <p><code class="varname">referral</code></p>
1833                   </td>
1834 <td>
1835                     <p>
1836                       The number of referrals the resolver received
1837                       throughout the resolution process.
1838                       In the above example this is 2, which are most
1839                       likely com and example.com.
1840                     </p>
1841                   </td>
1842 </tr>
1843 <tr>
1844 <td>
1845                     <p><code class="varname">restart</code></p>
1846                   </td>
1847 <td>
1848                     <p>
1849                       The number of cycles that the resolver tried
1850                       remote servers at the <code class="varname">domain</code>
1851                       zone.
1852                       In each cycle the resolver sends one query
1853                       (possibly resending it, depending on the response)
1854                       to each known name server of
1855                       the <code class="varname">domain</code> zone.
1856                     </p>
1857                   </td>
1858 </tr>
1859 <tr>
1860 <td>
1861                     <p><code class="varname">qrysent</code></p>
1862                   </td>
1863 <td>
1864                     <p>
1865                       The number of queries the resolver sent at the
1866                       <code class="varname">domain</code> zone.
1867                     </p>
1868                   </td>
1869 </tr>
1870 <tr>
1871 <td>
1872                     <p><code class="varname">timeout</code></p>
1873                   </td>
1874 <td>
1875                     <p>
1876                       The number of timeouts since the resolver
1877                       received the last response.
1878                     </p>
1879                   </td>
1880 </tr>
1881 <tr>
1882 <td>
1883                     <p><code class="varname">lame</code></p>
1884                   </td>
1885 <td>
1886                     <p>
1887                       The number of lame servers the resolver detected
1888                       at the <code class="varname">domain</code> zone.
1889                       A server is detected to be lame either by an
1890                       invalid response or as a result of lookup in
1891                       BIND9's address database (ADB), where lame
1892                       servers are cached.
1893                     </p>
1894                   </td>
1895 </tr>
1896 <tr>
1897 <td>
1898                     <p><code class="varname">neterr</code></p>
1899                   </td>
1900 <td>
1901                     <p>
1902                       The number of erroneous results that the
1903                       resolver encountered in sending queries
1904                       at the <code class="varname">domain</code> zone.
1905                       One common case is the remote server is
1906                       unreachable and the resolver receives an ICMP
1907                       unreachable error message.
1908                     </p>
1909                   </td>
1910 </tr>
1911 <tr>
1912 <td>
1913                     <p><code class="varname">badresp</code></p>
1914                   </td>
1915 <td>
1916                     <p>
1917                       The number of unexpected responses (other than
1918                       <code class="varname">lame</code>) to queries sent by the
1919                       resolver at the <code class="varname">domain</code> zone.
1920                     </p>
1921                   </td>
1922 </tr>
1923 <tr>
1924 <td>
1925                     <p><code class="varname">adberr</code></p>
1926                   </td>
1927 <td>
1928                     <p>
1929                       Failures in finding remote server addresses
1930                       of the <code class="varname">domain</code> zone in the ADB.
1931                       One common case of this is that the remote
1932                       server's name does not have any address records.
1933                     </p>
1934                   </td>
1935 </tr>
1936 <tr>
1937 <td>
1938                     <p><code class="varname">findfail</code></p>
1939                   </td>
1940 <td>
1941                     <p>
1942                       Failures of resolving remote server addresses.
1943                       This is a total number of failures throughout
1944                       the resolution process.
1945                     </p>
1946                   </td>
1947 </tr>
1948 <tr>
1949 <td>
1950                     <p><code class="varname">valfail</code></p>
1951                   </td>
1952 <td>
1953                     <p>
1954                       Failures of DNSSEC validation.
1955                       Validation failures are counted throughout
1956                       the resolution process (not limited to
1957                       the <code class="varname">domain</code> zone), but should
1958                       only happen in <code class="varname">domain</code>.
1959                     </p>
1960                   </td>
1961 </tr>
1962 </tbody>
1963 </table></div>
1964 <p>
1965             At the debug levels of 3 or higher, the same messages
1966             as those at the debug 1 level are logged for other errors
1967             than SERVFAIL.
1968             Note that negative responses such as NXDOMAIN are not
1969             regarded as errors here.
1970           </p>
1971 <p>
1972             At the debug levels of 4 or higher, the same messages
1973             as those at the debug 2 level are logged for other errors
1974             than SERVFAIL.
1975             Unlike the above case of level 3, messages are logged for
1976             negative responses.
1977             This is because any unexpected results can be difficult to
1978             debug in the recursion case.
1979           </p>
1980 </div>
1981 </div>
1982 <div class="sect2" lang="en">
1983 <div class="titlepage"><div><div><h3 class="title">
1984 <a name="id2577496"></a><span><strong class="command">lwres</strong></span> Statement Grammar</h3></div></div></div>
1985 <p>
1986            This is the grammar of the <span><strong class="command">lwres</strong></span>
1987           statement in the <code class="filename">named.conf</code> file:
1988         </p>
1989 <pre class="programlisting"><span><strong class="command">lwres</strong></span> {
1990     [<span class="optional"> listen-on { <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ;
1991                 [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; ... </span>] }; </span>]
1992     [<span class="optional"> view <em class="replaceable"><code>view_name</code></em>; </span>]
1993     [<span class="optional"> search { <em class="replaceable"><code>domain_name</code></em> ; [<span class="optional"> <em class="replaceable"><code>domain_name</code></em> ; ... </span>] }; </span>]
1994     [<span class="optional"> ndots <em class="replaceable"><code>number</code></em>; </span>]
1995 };
1996 </pre>
1997 </div>
1998 <div class="sect2" lang="en">
1999 <div class="titlepage"><div><div><h3 class="title">
2000 <a name="id2577570"></a><span><strong class="command">lwres</strong></span> Statement Definition and Usage</h3></div></div></div>
2001 <p>
2002           The <span><strong class="command">lwres</strong></span> statement configures the
2003           name
2004           server to also act as a lightweight resolver server. (See
2005           <a href="Bv9ARM.ch05.html#lwresd" title="Running a Resolver Daemon">the section called &#8220;Running a Resolver Daemon&#8221;</a>.)  There may be multiple
2006           <span><strong class="command">lwres</strong></span> statements configuring
2007           lightweight resolver servers with different properties.
2008         </p>
2009 <p>
2010           The <span><strong class="command">listen-on</strong></span> statement specifies a
2011           list of
2012           addresses (and ports) that this instance of a lightweight resolver
2013           daemon
2014           should accept requests on.  If no port is specified, port 921 is
2015           used.
2016           If this statement is omitted, requests will be accepted on
2017           127.0.0.1,
2018           port 921.
2019         </p>
2020 <p>
2021           The <span><strong class="command">view</strong></span> statement binds this
2022           instance of a
2023           lightweight resolver daemon to a view in the DNS namespace, so that
2024           the
2025           response will be constructed in the same manner as a normal DNS
2026           query
2027           matching this view.  If this statement is omitted, the default view
2028           is
2029           used, and if there is no default view, an error is triggered.
2030         </p>
2031 <p>
2032           The <span><strong class="command">search</strong></span> statement is equivalent to
2033           the
2034           <span><strong class="command">search</strong></span> statement in
2035           <code class="filename">/etc/resolv.conf</code>.  It provides a
2036           list of domains
2037           which are appended to relative names in queries.
2038         </p>
2039 <p>
2040           The <span><strong class="command">ndots</strong></span> statement is equivalent to
2041           the
2042           <span><strong class="command">ndots</strong></span> statement in
2043           <code class="filename">/etc/resolv.conf</code>.  It indicates the
2044           minimum
2045           number of dots in a relative domain name that should result in an
2046           exact match lookup before search path elements are appended.
2047         </p>
2048 </div>
2049 <div class="sect2" lang="en">
2050 <div class="titlepage"><div><div><h3 class="title">
2051 <a name="id2577702"></a><span><strong class="command">masters</strong></span> Statement Grammar</h3></div></div></div>
2052 <pre class="programlisting">
2053 <span><strong class="command">masters</strong></span> <em class="replaceable"><code>name</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] { ( <em class="replaceable"><code>masters_list</code></em> |
2054       <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] };
2055 </pre>
2056 </div>
2057 <div class="sect2" lang="en">
2058 <div class="titlepage"><div><div><h3 class="title">
2059 <a name="id2577746"></a><span><strong class="command">masters</strong></span> Statement Definition and
2060           Usage</h3></div></div></div>
2061 <p><span><strong class="command">masters</strong></span>
2062           lists allow for a common set of masters to be easily used by
2063           multiple stub and slave zones.
2064         </p>
2065 </div>
2066 <div class="sect2" lang="en">
2067 <div class="titlepage"><div><div><h3 class="title">
2068 <a name="id2577761"></a><span><strong class="command">options</strong></span> Statement Grammar</h3></div></div></div>
2069 <p>
2070           This is the grammar of the <span><strong class="command">options</strong></span>
2071           statement in the <code class="filename">named.conf</code> file:
2072         </p>
2073 <pre class="programlisting"><span><strong class="command">options</strong></span> {
2074     [<span class="optional"> attach-cache <em class="replaceable"><code>cache_name</code></em>; </span>]
2075     [<span class="optional"> version <em class="replaceable"><code>version_string</code></em>; </span>]
2076     [<span class="optional"> hostname <em class="replaceable"><code>hostname_string</code></em>; </span>]
2077     [<span class="optional"> server-id <em class="replaceable"><code>server_id_string</code></em>; </span>]
2078     [<span class="optional"> directory <em class="replaceable"><code>path_name</code></em>; </span>]
2079     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2080     [<span class="optional"> managed-keys-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2081     [<span class="optional"> named-xfer <em class="replaceable"><code>path_name</code></em>; </span>]
2082     [<span class="optional"> tkey-gssapi-credential <em class="replaceable"><code>principal</code></em>; </span>]
2083     [<span class="optional"> tkey-domain <em class="replaceable"><code>domainname</code></em>; </span>]
2084     [<span class="optional"> tkey-dhkey <em class="replaceable"><code>key_name</code></em> <em class="replaceable"><code>key_tag</code></em>; </span>]
2085     [<span class="optional"> cache-file <em class="replaceable"><code>path_name</code></em>; </span>]
2086     [<span class="optional"> dump-file <em class="replaceable"><code>path_name</code></em>; </span>]
2087     [<span class="optional"> bindkeys-file <em class="replaceable"><code>path_name</code></em>; </span>]
2088     [<span class="optional"> memstatistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2089     [<span class="optional"> memstatistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2090     [<span class="optional"> pid-file <em class="replaceable"><code>path_name</code></em>; </span>]
2091     [<span class="optional"> recursing-file <em class="replaceable"><code>path_name</code></em>; </span>]
2092     [<span class="optional"> statistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2093     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2094     [<span class="optional"> auth-nxdomain <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2095     [<span class="optional"> deallocate-on-exit <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2096     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em>; </span>]
2097     [<span class="optional"> fake-iquery <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2098     [<span class="optional"> fetch-glue <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2099     [<span class="optional"> flush-zones-on-shutdown <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2100     [<span class="optional"> has-old-clients <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2101     [<span class="optional"> host-statistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2102     [<span class="optional"> host-statistics-max <em class="replaceable"><code>number</code></em>; </span>]
2103     [<span class="optional"> minimal-responses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2104     [<span class="optional"> multiple-cnames <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2105     [<span class="optional"> notify <em class="replaceable"><code>yes_or_no</code></em> | <em class="replaceable"><code>explicit</code></em> | <em class="replaceable"><code>master-only</code></em>; </span>]
2106     [<span class="optional"> recursion <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2107     [<span class="optional"> rfc2308-type1 <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2108     [<span class="optional"> use-id-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2109     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2110     [<span class="optional"> ixfr-from-differences (<em class="replaceable"><code>yes_or_no</code></em> | <code class="constant">master</code> | <code class="constant">slave</code>); </span>]
2111     [<span class="optional"> dnssec-enable <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2112     [<span class="optional"> dnssec-validation <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2113     [<span class="optional"> dnssec-lookaside ( <em class="replaceable"><code>auto</code></em> |
2114                         <em class="replaceable"><code>domain</code></em> trust-anchor <em class="replaceable"><code>domain</code></em> ); </span>]
2115     [<span class="optional"> dnssec-must-be-secure <em class="replaceable"><code>domain yes_or_no</code></em>; </span>]
2116     [<span class="optional"> dnssec-accept-expired <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2117     [<span class="optional"> forward ( <em class="replaceable"><code>only</code></em> | <em class="replaceable"><code>first</code></em> ); </span>]
2118     [<span class="optional"> forwarders { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; ... </span>] }; </span>]
2119     [<span class="optional"> dual-stack-servers [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] {
2120         ( <em class="replaceable"><code>domain_name</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] |
2121           <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ) ;
2122         ... }; </span>]
2123     [<span class="optional"> check-names ( <em class="replaceable"><code>master</code></em> | <em class="replaceable"><code>slave</code></em> | <em class="replaceable"><code>response</code></em> )
2124         ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2125     [<span class="optional"> check-dup-records ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2126     [<span class="optional"> check-mx ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2127     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2128     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2129     [<span class="optional"> check-mx-cname ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2130     [<span class="optional"> check-srv-cname ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2131     [<span class="optional"> check-sibling <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2132     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2133     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2134     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2135     [<span class="optional"> allow-query-cache { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2136     [<span class="optional"> allow-query-cache-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2137     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2138     [<span class="optional"> allow-recursion { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2139     [<span class="optional"> allow-recursion-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2140     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2141     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2142     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2143     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2144     [<span class="optional"> dnssec-secure-to-insecure <em class="replaceable"><code>yes_or_no</code></em> ;</span>]
2145     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2146     [<span class="optional"> allow-v6-synthesis { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2147     [<span class="optional"> blackhole { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2148     [<span class="optional"> use-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2149     [<span class="optional"> avoid-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2150     [<span class="optional"> use-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2151     [<span class="optional"> avoid-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2152     [<span class="optional"> listen-on [<span class="optional"> port <em class="replaceable"><code>ip_port</code></em> </span>] { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2153     [<span class="optional"> listen-on-v6 [<span class="optional"> port <em class="replaceable"><code>ip_port</code></em> </span>] { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2154     [<span class="optional"> query-source ( ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2155         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
2156         [<span class="optional"> address ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2157         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
2158     [<span class="optional"> query-source-v6 ( ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2159         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
2160         [<span class="optional"> address ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2161         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
2162     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2163     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
2164     [<span class="optional"> queryport-pool-updateinterval <em class="replaceable"><code>number</code></em>; </span>]
2165     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em>; </span>]
2166     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em>; </span>]
2167     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em>; </span>]
2168     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em>; </span>]
2169     [<span class="optional"> tcp-clients <em class="replaceable"><code>number</code></em>; </span>]
2170     [<span class="optional"> reserved-sockets <em class="replaceable"><code>number</code></em>; </span>]
2171     [<span class="optional"> recursive-clients <em class="replaceable"><code>number</code></em>; </span>]
2172     [<span class="optional"> serial-query-rate <em class="replaceable"><code>number</code></em>; </span>]
2173     [<span class="optional"> serial-queries <em class="replaceable"><code>number</code></em>; </span>]
2174     [<span class="optional"> tcp-listen-queue <em class="replaceable"><code>number</code></em>; </span>]
2175     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em>; </span>]
2176     [<span class="optional"> transfers-in  <em class="replaceable"><code>number</code></em>; </span>]
2177     [<span class="optional"> transfers-out <em class="replaceable"><code>number</code></em>; </span>]
2178     [<span class="optional"> transfers-per-ns <em class="replaceable"><code>number</code></em>; </span>]
2179     [<span class="optional"> transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
2180     [<span class="optional"> transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
2181     [<span class="optional"> alt-transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
2182     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
2183                              [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
2184     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2185     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
2186     [<span class="optional"> notify-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
2187     [<span class="optional"> notify-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
2188     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2189     [<span class="optional"> also-notify { <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ;
2190                   [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; ... </span>] }; </span>]
2191     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em>; </span>]
2192     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
2193     [<span class="optional"> coresize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2194     [<span class="optional"> datasize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2195     [<span class="optional"> files <em class="replaceable"><code>size_spec</code></em> ; </span>]
2196     [<span class="optional"> stacksize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2197     [<span class="optional"> cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2198     [<span class="optional"> heartbeat-interval <em class="replaceable"><code>number</code></em>; </span>]
2199     [<span class="optional"> interface-interval <em class="replaceable"><code>number</code></em>; </span>]
2200     [<span class="optional"> statistics-interval <em class="replaceable"><code>number</code></em>; </span>]
2201     [<span class="optional"> topology { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2202     [<span class="optional"> sortlist { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2203     [<span class="optional"> rrset-order { <em class="replaceable"><code>order_spec</code></em> ; [<span class="optional"> <em class="replaceable"><code>order_spec</code></em> ; ... </span>] </span>] };
2204     [<span class="optional"> lame-ttl <em class="replaceable"><code>number</code></em>; </span>]
2205     [<span class="optional"> max-ncache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2206     [<span class="optional"> max-cache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2207     [<span class="optional"> sig-validity-interval <em class="replaceable"><code>number</code></em> [<span class="optional"><em class="replaceable"><code>number</code></em></span>] ; </span>]
2208     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
2209     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
2210     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
2211     [<span class="optional"> min-roots <em class="replaceable"><code>number</code></em>; </span>]
2212     [<span class="optional"> use-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2213     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2214     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2215     [<span class="optional"> treat-cr-as-space <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2216     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2217     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2218     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2219     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2220     [<span class="optional"> port <em class="replaceable"><code>ip_port</code></em>; </span>]
2221     [<span class="optional"> additional-from-auth <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2222     [<span class="optional"> additional-from-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2223     [<span class="optional"> random-device <em class="replaceable"><code>path_name</code></em> ; </span>]
2224     [<span class="optional"> max-cache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2225     [<span class="optional"> match-mapped-addresses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2226     [<span class="optional"> filter-aaaa-on-v4 ( <em class="replaceable"><code>yes_or_no</code></em> | <em class="replaceable"><code>break-dnssec</code></em> ); </span>]
2227     [<span class="optional"> preferred-glue ( <em class="replaceable"><code>A</code></em> | <em class="replaceable"><code>AAAA</code></em> | <em class="replaceable"><code>NONE</code></em> ); </span>]
2228     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2229     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2230     [<span class="optional"> root-delegation-only [<span class="optional"> exclude { <em class="replaceable"><code>namelist</code></em> } </span>] ; </span>]
2231     [<span class="optional"> querylog <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2232     [<span class="optional"> disable-algorithms <em class="replaceable"><code>domain</code></em> { <em class="replaceable"><code>algorithm</code></em>;
2233                                 [<span class="optional"> <em class="replaceable"><code>algorithm</code></em>; </span>] }; </span>]
2234     [<span class="optional"> acache-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2235     [<span class="optional"> acache-cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2236     [<span class="optional"> max-acache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2237     [<span class="optional"> clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2238     [<span class="optional"> max-clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2239     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
2240     [<span class="optional"> empty-server <em class="replaceable"><code>name</code></em> ; </span>]
2241     [<span class="optional"> empty-contact <em class="replaceable"><code>name</code></em> ; </span>]
2242     [<span class="optional"> empty-zones-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2243     [<span class="optional"> disable-empty-zone <em class="replaceable"><code>zone_name</code></em> ; </span>]
2244     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2245     [<span class="optional"> zero-no-soa-ttl-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2246     [<span class="optional"> deny-answer-addresses { <em class="replaceable"><code>address_match_list</code></em> } [<span class="optional"> except-from { <em class="replaceable"><code>namelist</code></em> } </span>];</span>]
2247     [<span class="optional"> deny-answer-aliases { <em class="replaceable"><code>namelist</code></em> } [<span class="optional"> except-from { <em class="replaceable"><code>namelist</code></em> } </span>];</span>]
2248 };
2249 </pre>
2250 </div>
2251 <div class="sect2" lang="en">
2252 <div class="titlepage"><div><div><h3 class="title">
2253 <a name="options"></a><span><strong class="command">options</strong></span> Statement Definition and
2254           Usage</h3></div></div></div>
2255 <p>
2256           The <span><strong class="command">options</strong></span> statement sets up global
2257           options
2258           to be used by <acronym class="acronym">BIND</acronym>. This statement
2259           may appear only
2260           once in a configuration file. If there is no <span><strong class="command">options</strong></span>
2261           statement, an options block with each option set to its default will
2262           be used.
2263         </p>
2264 <div class="variablelist"><dl>
2265 <dt><span class="term"><span><strong class="command">attach-cache</strong></span></span></dt>
2266 <dd>
2267 <p>
2268                   Allows multiple views to share a single cache
2269                   database.
2270                   Each view has its own cache database by default, but
2271                   if multiple views have the same operational policy
2272                   for name resolution and caching, those views can
2273                   share a single cache to save memory and possibly
2274                   improve resolution efficiency by using this option.
2275                 </p>
2276 <p>
2277                   The <span><strong class="command">attach-cache</strong></span> option
2278                   may also be specified in <span><strong class="command">view</strong></span>
2279                   statements, in which case it overrides the
2280                   global <span><strong class="command">attach-cache</strong></span> option.
2281                 </p>
2282 <p>
2283                   The <em class="replaceable"><code>cache_name</code></em> specifies
2284                   the cache to be shared.
2285                   When the <span><strong class="command">named</strong></span> server configures
2286                   views which are supposed to share a cache, it
2287                   creates a cache with the specified name for the
2288                   first view of these sharing views.
2289                   The rest of the views will simply refer to the
2290                   already created cache.
2291                 </p>
2292 <p>
2293                   One common configuration to share a cache would be to
2294                   allow all views to share a single cache.
2295                   This can be done by specifying
2296                   the <span><strong class="command">attach-cache</strong></span> as a global
2297                   option with an arbitrary name.
2298                 </p>
2299 <p>
2300                   Another possible operation is to allow a subset of
2301                   all views to share a cache while the others to
2302                   retain their own caches.
2303                   For example, if there are three views A, B, and C,
2304                   and only A and B should share a cache, specify the
2305                   <span><strong class="command">attach-cache</strong></span> option as a view A (or
2306                   B)'s option, referring to the other view name:
2307                 </p>
2308 <pre class="programlisting">
2309   view "A" {
2310     // this view has its own cache
2311     ...
2312   };
2313   view "B" {
2314     // this view refers to A's cache
2315     attach-cache "A";
2316   };
2317   view "C" {
2318     // this view has its own cache
2319     ...
2320   };
2321 </pre>
2322 <p>
2323                   Views that share a cache must have the same policy
2324                   on configurable parameters that may affect caching.
2325                   The current implementation requires the following
2326                   configurable options be consistent among these
2327                   views:
2328                   <span><strong class="command">check-names</strong></span>,
2329                   <span><strong class="command">cleaning-interval</strong></span>,
2330                   <span><strong class="command">dnssec-accept-expired</strong></span>,
2331                   <span><strong class="command">dnssec-validation</strong></span>,
2332                   <span><strong class="command">max-cache-ttl</strong></span>,
2333                   <span><strong class="command">max-ncache-ttl</strong></span>,
2334                   <span><strong class="command">max-cache-size</strong></span>, and
2335                   <span><strong class="command">zero-no-soa-ttl</strong></span>.
2336                 </p>
2337 <p>
2338                   Note that there may be other parameters that may
2339                   cause confusion if they are inconsistent for
2340                   different views that share a single cache.
2341                   For example, if these views define different sets of
2342                   forwarders that can return different answers for the
2343                   same question, sharing the answer does not make
2344                   sense or could even be harmful.
2345                   It is administrator's responsibility to ensure
2346                   configuration differences in different views do
2347                   not cause disruption with a shared cache.
2348                 </p>
2349 </dd>
2350 <dt><span class="term"><span><strong class="command">directory</strong></span></span></dt>
2351 <dd><p>
2352                 The working directory of the server.
2353                 Any non-absolute pathnames in the configuration file will be
2354                 taken
2355                 as relative to this directory. The default location for most
2356                 server
2357                 output files (e.g. <code class="filename">named.run</code>)
2358                 is this directory.
2359                 If a directory is not specified, the working directory
2360                 defaults to `<code class="filename">.</code>', the directory from
2361                 which the server
2362                 was started. The directory specified should be an absolute
2363                 path.
2364               </p></dd>
2365 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
2366 <dd><p>
2367                 When performing dynamic update of secure zones, the
2368                 directory where the public and private DNSSEC key files
2369                 should be found, if different than the current working
2370                 directory.  (Note that this option has no effect on the
2371                 paths for files containing non-DNSSEC keys such as
2372                 <code class="filename">bind.keys</code>,
2373                 <code class="filename">rndc.key</code> or
2374                 <code class="filename">session.key</code>.)
2375               </p></dd>
2376 <dt><span class="term"><span><strong class="command">managed-keys-directory</strong></span></span></dt>
2377 <dd><p>
2378                 The directory used to hold the files used to track managed keys.
2379                 By default it is the working directory.  It there are no
2380                 views then the file <code class="filename">managed-keys.bind</code>
2381                 otherwise a SHA256 hash of the view name is used with
2382                 <code class="filename">.mkeys</code> extension added.
2383               </p></dd>
2384 <dt><span class="term"><span><strong class="command">named-xfer</strong></span></span></dt>
2385 <dd><p>
2386                 <span class="emphasis"><em>This option is obsolete.</em></span> It
2387                 was used in <acronym class="acronym">BIND</acronym> 8 to specify
2388                 the pathname to the <span><strong class="command">named-xfer</strong></span>
2389                 program.  In <acronym class="acronym">BIND</acronym> 9, no separate
2390                 <span><strong class="command">named-xfer</strong></span> program is needed;
2391                 its functionality is built into the name server.
2392               </p></dd>
2393 <dt><span class="term"><span><strong class="command">tkey-gssapi-credential</strong></span></span></dt>
2394 <dd><p>
2395                 The security credential with which the server should
2396                 authenticate keys requested by the GSS-TSIG protocol.
2397                 Currently only Kerberos 5 authentication is available
2398                 and the credential is a Kerberos principal which
2399                 the server can acquire through the default system
2400                 key file, normally <code class="filename">/etc/krb5.keytab</code>.
2401                 Normally this principal is of the form
2402                 "<strong class="userinput"><code>dns/</code></strong><code class="varname">server.domain</code>".
2403                 To use GSS-TSIG, <span><strong class="command">tkey-domain</strong></span>
2404                 must also be set.
2405               </p></dd>
2406 <dt><span class="term"><span><strong class="command">tkey-domain</strong></span></span></dt>
2407 <dd><p>
2408                 The domain appended to the names of all shared keys
2409                 generated with <span><strong class="command">TKEY</strong></span>.  When a
2410                 client requests a <span><strong class="command">TKEY</strong></span> exchange,
2411                 it may or may not specify the desired name for the
2412                 key. If present, the name of the shared key will
2413                 be <code class="varname">client specified part</code> +
2414                 <code class="varname">tkey-domain</code>.  Otherwise, the
2415                 name of the shared key will be <code class="varname">random hex
2416                 digits</code> + <code class="varname">tkey-domain</code>.
2417                 In most cases, the <span><strong class="command">domainname</strong></span>
2418                 should be the server's domain name, or an otherwise
2419                 non-existent subdomain like
2420                 "_tkey.<code class="varname">domainname</code>".  If you are
2421                 using GSS-TSIG, this variable must be defined.
2422               </p></dd>
2423 <dt><span class="term"><span><strong class="command">tkey-dhkey</strong></span></span></dt>
2424 <dd><p>
2425                 The Diffie-Hellman key used by the server
2426                 to generate shared keys with clients using the Diffie-Hellman
2427                 mode
2428                 of <span><strong class="command">TKEY</strong></span>. The server must be
2429                 able to load the
2430                 public and private keys from files in the working directory.
2431                 In
2432                 most cases, the keyname should be the server's host name.
2433               </p></dd>
2434 <dt><span class="term"><span><strong class="command">cache-file</strong></span></span></dt>
2435 <dd><p>
2436                 This is for testing only.  Do not use.
2437               </p></dd>
2438 <dt><span class="term"><span><strong class="command">dump-file</strong></span></span></dt>
2439 <dd><p>
2440                 The pathname of the file the server dumps
2441                 the database to when instructed to do so with
2442                 <span><strong class="command">rndc dumpdb</strong></span>.
2443                 If not specified, the default is <code class="filename">named_dump.db</code>.
2444               </p></dd>
2445 <dt><span class="term"><span><strong class="command">memstatistics-file</strong></span></span></dt>
2446 <dd><p>
2447                 The pathname of the file the server writes memory
2448                 usage statistics to on exit. If not specified,
2449                 the default is <code class="filename">named.memstats</code>.
2450               </p></dd>
2451 <dt><span class="term"><span><strong class="command">pid-file</strong></span></span></dt>
2452 <dd><p>
2453                 The pathname of the file the server writes its process ID
2454                 in. If not specified, the default is
2455                 <code class="filename">/var/run/named/named.pid</code>.
2456                 The PID file is used by programs that want to send signals to
2457                 the running
2458                 name server. Specifying <span><strong class="command">pid-file none</strong></span> disables the
2459                 use of a PID file &#8212; no file will be written and any
2460                 existing one will be removed.  Note that <span><strong class="command">none</strong></span>
2461                 is a keyword, not a filename, and therefore is not enclosed
2462                 in
2463                 double quotes.
2464               </p></dd>
2465 <dt><span class="term"><span><strong class="command">recursing-file</strong></span></span></dt>
2466 <dd><p>
2467                 The pathname of the file the server dumps
2468                 the queries that are currently recursing when instructed
2469                 to do so with <span><strong class="command">rndc recursing</strong></span>.
2470                 If not specified, the default is <code class="filename">named.recursing</code>.
2471               </p></dd>
2472 <dt><span class="term"><span><strong class="command">statistics-file</strong></span></span></dt>
2473 <dd><p>
2474                 The pathname of the file the server appends statistics
2475                 to when instructed to do so using <span><strong class="command">rndc stats</strong></span>.
2476                 If not specified, the default is <code class="filename">named.stats</code> in the
2477                 server's current directory.  The format of the file is
2478                 described
2479                 in <a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
2480               </p></dd>
2481 <dt><span class="term"><span><strong class="command">bindkeys-file</strong></span></span></dt>
2482 <dd><p>
2483                 The pathname of a file to override the built-in trusted
2484                 keys provided by <span><strong class="command">named</strong></span>.
2485                 See the discussion of <span><strong class="command">dnssec-lookaside</strong></span>
2486                 for details.  If not specified, the default is
2487                 <code class="filename">/etc/bind.keys</code>.
2488               </p></dd>
2489 <dt><span class="term"><span><strong class="command">session-keyfile</strong></span></span></dt>
2490 <dd><p>
2491                 The pathname of the file into which to write a TSIG
2492                 session key generated by <span><strong class="command">named</strong></span> for use by
2493                 <span><strong class="command">nsupdate -l</strong></span>.  If not specified, the
2494                 default is <code class="filename">/var/run/named/session.key</code>.
2495                 (See <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>, and in
2496                 particular the discussion of the
2497                 <span><strong class="command">update-policy</strong></span> statement's
2498                 <strong class="userinput"><code>local</code></strong> option for more
2499                 information about this feature.)
2500               </p></dd>
2501 <dt><span class="term"><span><strong class="command">session-keyname</strong></span></span></dt>
2502 <dd><p>
2503                 The key name to use for the TSIG session key.
2504                 If not specified, the default is "local-ddns".
2505               </p></dd>
2506 <dt><span class="term"><span><strong class="command">session-keyalg</strong></span></span></dt>
2507 <dd><p>
2508                 The algorithm to use for the TSIG session key.
2509                 Valid values are hmac-sha1, hmac-sha224, hmac-sha256,
2510                 hmac-sha384, hmac-sha512 and hmac-md5.  If not
2511                 specified, the default is hmac-sha256.
2512               </p></dd>
2513 <dt><span class="term"><span><strong class="command">session-keyfile</strong></span></span></dt>
2514 <dd><p>
2515                 The pathname of the file into which to write a session TSIG
2516                 key for use by <span><strong class="command">nsupdate -l</strong></span>.  (See the
2517                 discussion of the <span><strong class="command">update-policy</strong></span>
2518                 statement's <strong class="userinput"><code>local</code></strong> option for more
2519                 details on this feature.)
2520               </p></dd>
2521 <dt><span class="term"><span><strong class="command">port</strong></span></span></dt>
2522 <dd><p>
2523                 The UDP/TCP port number the server uses for
2524                 receiving and sending DNS protocol traffic.
2525                 The default is 53.  This option is mainly intended for server
2526                 testing;
2527                 a server using a port other than 53 will not be able to
2528                 communicate with
2529                 the global DNS.
2530               </p></dd>
2531 <dt><span class="term"><span><strong class="command">random-device</strong></span></span></dt>
2532 <dd><p>
2533                 The source of entropy to be used by the server.  Entropy is
2534                 primarily needed
2535                 for DNSSEC operations, such as TKEY transactions and dynamic
2536                 update of signed
2537                 zones.  This options specifies the device (or file) from which
2538                 to read
2539                 entropy.  If this is a file, operations requiring entropy will
2540                 fail when the
2541                 file has been exhausted.  If not specified, the default value
2542                 is
2543                 <code class="filename">/dev/random</code>
2544                 (or equivalent) when present, and none otherwise.  The
2545                 <span><strong class="command">random-device</strong></span> option takes
2546                 effect during
2547                 the initial configuration load at server startup time and
2548                 is ignored on subsequent reloads.
2549               </p></dd>
2550 <dt><span class="term"><span><strong class="command">preferred-glue</strong></span></span></dt>
2551 <dd><p>
2552                 If specified, the listed type (A or AAAA) will be emitted
2553                 before other glue
2554                 in the additional section of a query response.
2555                 The default is not to prefer any type (NONE).
2556               </p></dd>
2557 <dt>
2558 <a name="root_delegation_only"></a><span class="term"><span><strong class="command">root-delegation-only</strong></span></span>
2559 </dt>
2560 <dd>
2561 <p>
2562                 Turn on enforcement of delegation-only in TLDs
2563                 (top level domains) and root zones with an optional
2564                 exclude list.
2565               </p>
2566 <p>
2567                 DS queries are expected to be made to and be answered by
2568                 delegation only zones.  Such queries and responses are
2569                 treated as an exception to delegation-only processing
2570                 and are not converted to NXDOMAIN responses provided
2571                 a CNAME is not discovered at the query name.
2572               </p>
2573 <p>
2574                 If a delegation only zone server also serves a child
2575                 zone it is not always possible to determine whether
2576                 an answer comes from the delegation only zone or the
2577                 child zone.  SOA NS and DNSKEY records are apex
2578                 only records and a matching response that contains
2579                 these records or DS is treated as coming from a
2580                 child zone.  RRSIG records are also examined to see
2581                 if they are signed by a child zone or not.  The
2582                 authority section is also examined to see if there
2583                 is evidence that the answer is from the child zone.
2584                 Answers that are determined to be from a child zone
2585                 are not converted to NXDOMAIN responses.  Despite
2586                 all these checks there is still a possibility of
2587                 false negatives when a child zone is being served.
2588               </p>
2589 <p>
2590                 Similarly false positives can arise from empty nodes
2591                 (no records at the name) in the delegation only zone
2592                 when the query type is not ANY.
2593               </p>
2594 <p>
2595                 Note some TLDs are not delegation only (e.g. "DE", "LV",
2596                 "US" and "MUSEUM").  This list is not exhaustive.
2597               </p>
2598 <pre class="programlisting">
2599 options {
2600         root-delegation-only exclude { "de"; "lv"; "us"; "museum"; };
2601 };
2602 </pre>
2603 </dd>
2604 <dt><span class="term"><span><strong class="command">disable-algorithms</strong></span></span></dt>
2605 <dd><p>
2606                 Disable the specified DNSSEC algorithms at and below the
2607                 specified name.
2608                 Multiple <span><strong class="command">disable-algorithms</strong></span>
2609                 statements are allowed.
2610                 Only the most specific will be applied.
2611               </p></dd>
2612 <dt><span class="term"><span><strong class="command">dnssec-lookaside</strong></span></span></dt>
2613 <dd>
2614 <p>
2615                 When set, <span><strong class="command">dnssec-lookaside</strong></span> provides the
2616                 validator with an alternate method to validate DNSKEY
2617                 records at the top of a zone.  When a DNSKEY is at or
2618                 below a domain specified by the deepest
2619                 <span><strong class="command">dnssec-lookaside</strong></span>, and the normal DNSSEC
2620                 validation has left the key untrusted, the trust-anchor
2621                 will be appended to the key name and a DLV record will be
2622                 looked up to see if it can validate the key.  If the DLV
2623                 record validates a DNSKEY (similarly to the way a DS
2624                 record does) the DNSKEY RRset is deemed to be trusted.
2625               </p>
2626 <p>
2627                 If <span><strong class="command">dnssec-lookaside</strong></span> is set to
2628                 <strong class="userinput"><code>auto</code></strong>, then built-in default
2629                 values for the DLV domain and trust anchor will be
2630                 used, along with a built-in key for validation.
2631               </p>
2632 <p>
2633                 The default DLV key is stored in the file
2634                 <code class="filename">bind.keys</code>, which
2635                 <span><strong class="command">named</strong></span> loads at startup if
2636                 <span><strong class="command">dnssec-lookaside</strong></span> is set to
2637                 <code class="constant">auto</code>.  A copy of that file is
2638                 installed along with <acronym class="acronym">BIND</acronym> 9, and is
2639                 current as of the release date.  If the DLV key expires, a
2640                 new copy of <code class="filename">bind.keys</code> can be downloaded
2641                 from <a href="" target="_top">https://www.isc.org/solutions/dlv</a>.
2642               </p>
2643 <p>
2644                 (To prevent problems if <code class="filename">bind.keys</code> is
2645                 not found, the current key is also compiled in to
2646                 <span><strong class="command">named</strong></span>.  Relying on this is not
2647                 recommended, however, as it requires <span><strong class="command">named</strong></span>
2648                 to be recompiled with a new key when the DLV key expires.)
2649               </p>
2650 <p>
2651                 NOTE: Using <code class="filename">bind.keys</code> to store
2652                 locally-configured keys is possible, but not
2653                 recommended, as the file will be overwritten whenever
2654                 <acronym class="acronym">BIND</acronym> 9 is re-installed or upgraded.
2655               </p>
2656 </dd>
2657 <dt><span class="term"><span><strong class="command">dnssec-must-be-secure</strong></span></span></dt>
2658 <dd><p>
2659                 Specify hierarchies which must be or may not be secure
2660                 (signed and validated).  If <strong class="userinput"><code>yes</code></strong>,
2661                 then <span><strong class="command">named</strong></span> will only accept answers if
2662                 they are secure.  If <strong class="userinput"><code>no</code></strong>, then normal
2663                 DNSSEC validation applies allowing for insecure answers to
2664                 be accepted.  The specified domain must be under a
2665                 <span><strong class="command">trusted-keys</strong></span> or
2666                 <span><strong class="command">managed-keys</strong></span> statement, or
2667                 <span><strong class="command">dnssec-lookaside</strong></span> must be active.
2668               </p></dd>
2669 </dl></div>
2670 <div class="sect3" lang="en">
2671 <div class="titlepage"><div><div><h4 class="title">
2672 <a name="boolean_options"></a>Boolean Options</h4></div></div></div>
2673 <div class="variablelist"><dl>
2674 <dt><span class="term"><span><strong class="command">auth-nxdomain</strong></span></span></dt>
2675 <dd><p>
2676                   If <strong class="userinput"><code>yes</code></strong>, then the <span><strong class="command">AA</strong></span> bit
2677                   is always set on NXDOMAIN responses, even if the server is
2678                   not actually
2679                   authoritative. The default is <strong class="userinput"><code>no</code></strong>;
2680                   this is
2681                   a change from <acronym class="acronym">BIND</acronym> 8. If you
2682                   are using very old DNS software, you
2683                   may need to set it to <strong class="userinput"><code>yes</code></strong>.
2684                 </p></dd>
2685 <dt><span class="term"><span><strong class="command">deallocate-on-exit</strong></span></span></dt>
2686 <dd><p>
2687                   This option was used in <acronym class="acronym">BIND</acronym>
2688                   8 to enable checking
2689                   for memory leaks on exit. <acronym class="acronym">BIND</acronym> 9 ignores the option and always performs
2690                   the checks.
2691                 </p></dd>
2692 <dt><span class="term"><span><strong class="command">memstatistics</strong></span></span></dt>
2693 <dd><p>
2694                   Write memory statistics to the file specified by
2695                   <span><strong class="command">memstatistics-file</strong></span> at exit.
2696                   The default is <strong class="userinput"><code>no</code></strong> unless
2697                   '-m record' is specified on the command line in
2698                   which case it is <strong class="userinput"><code>yes</code></strong>.
2699                 </p></dd>
2700 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
2701 <dd>
2702 <p>
2703                   If <strong class="userinput"><code>yes</code></strong>, then the
2704                   server treats all zones as if they are doing zone transfers
2705                   across
2706                   a dial-on-demand dialup link, which can be brought up by
2707                   traffic
2708                   originating from this server. This has different effects
2709                   according
2710                   to zone type and concentrates the zone maintenance so that
2711                   it all
2712                   happens in a short interval, once every <span><strong class="command">heartbeat-interval</strong></span> and
2713                   hopefully during the one call. It also suppresses some of
2714                   the normal
2715                   zone maintenance traffic. The default is <strong class="userinput"><code>no</code></strong>.
2716                 </p>
2717 <p>
2718                   The <span><strong class="command">dialup</strong></span> option
2719                   may also be specified in the <span><strong class="command">view</strong></span> and
2720                   <span><strong class="command">zone</strong></span> statements,
2721                   in which case it overrides the global <span><strong class="command">dialup</strong></span>
2722                   option.
2723                 </p>
2724 <p>
2725                   If the zone is a master zone, then the server will send out a
2726                   NOTIFY
2727                   request to all the slaves (default). This should trigger the
2728                   zone serial
2729                   number check in the slave (providing it supports NOTIFY)
2730                   allowing the slave
2731                   to verify the zone while the connection is active.
2732                   The set of servers to which NOTIFY is sent can be controlled
2733                   by
2734                   <span><strong class="command">notify</strong></span> and <span><strong class="command">also-notify</strong></span>.
2735                 </p>
2736 <p>
2737                   If the
2738                   zone is a slave or stub zone, then the server will suppress
2739                   the regular
2740                   "zone up to date" (refresh) queries and only perform them
2741                   when the
2742                   <span><strong class="command">heartbeat-interval</strong></span> expires in
2743                   addition to sending
2744                   NOTIFY requests.
2745                 </p>
2746 <p>
2747                   Finer control can be achieved by using
2748                   <strong class="userinput"><code>notify</code></strong> which only sends NOTIFY
2749                   messages,
2750                   <strong class="userinput"><code>notify-passive</code></strong> which sends NOTIFY
2751                   messages and
2752                   suppresses the normal refresh queries, <strong class="userinput"><code>refresh</code></strong>
2753                   which suppresses normal refresh processing and sends refresh
2754                   queries
2755                   when the <span><strong class="command">heartbeat-interval</strong></span>
2756                   expires, and
2757                   <strong class="userinput"><code>passive</code></strong> which just disables normal
2758                   refresh
2759                   processing.
2760                 </p>
2761 <div class="informaltable"><table border="1">
2762 <colgroup>
2763 <col>
2764 <col>
2765 <col>
2766 <col>
2767 </colgroup>
2768 <tbody>
2769 <tr>
2770 <td>
2771                           <p>
2772                             dialup mode
2773                           </p>
2774                         </td>
2775 <td>
2776                           <p>
2777                             normal refresh
2778                           </p>
2779                         </td>
2780 <td>
2781                           <p>
2782                             heart-beat refresh
2783                           </p>
2784                         </td>
2785 <td>
2786                           <p>
2787                             heart-beat notify
2788                           </p>
2789                         </td>
2790 </tr>
2791 <tr>
2792 <td>
2793                           <p><span><strong class="command">no</strong></span> (default)</p>
2794                         </td>
2795 <td>
2796                           <p>
2797                             yes
2798                           </p>
2799                         </td>
2800 <td>
2801                           <p>
2802                             no
2803                           </p>
2804                         </td>
2805 <td>
2806                           <p>
2807                             no
2808                           </p>
2809                         </td>
2810 </tr>
2811 <tr>
2812 <td>
2813                           <p><span><strong class="command">yes</strong></span></p>
2814                         </td>
2815 <td>
2816                           <p>
2817                             no
2818                           </p>
2819                         </td>
2820 <td>
2821                           <p>
2822                             yes
2823                           </p>
2824                         </td>
2825 <td>
2826                           <p>
2827                             yes
2828                           </p>
2829                         </td>
2830 </tr>
2831 <tr>
2832 <td>
2833                           <p><span><strong class="command">notify</strong></span></p>
2834                         </td>
2835 <td>
2836                           <p>
2837                             yes
2838                           </p>
2839                         </td>
2840 <td>
2841                           <p>
2842                             no
2843                           </p>
2844                         </td>
2845 <td>
2846                           <p>
2847                             yes
2848                           </p>
2849                         </td>
2850 </tr>
2851 <tr>
2852 <td>
2853                           <p><span><strong class="command">refresh</strong></span></p>
2854                         </td>
2855 <td>
2856                           <p>
2857                             no
2858                           </p>
2859                         </td>
2860 <td>
2861                           <p>
2862                             yes
2863                           </p>
2864                         </td>
2865 <td>
2866                           <p>
2867                             no
2868                           </p>
2869                         </td>
2870 </tr>
2871 <tr>
2872 <td>
2873                           <p><span><strong class="command">passive</strong></span></p>
2874                         </td>
2875 <td>
2876                           <p>
2877                             no
2878                           </p>
2879                         </td>
2880 <td>
2881                           <p>
2882                             no
2883                           </p>
2884                         </td>
2885 <td>
2886                           <p>
2887                             no
2888                           </p>
2889                         </td>
2890 </tr>
2891 <tr>
2892 <td>
2893                           <p><span><strong class="command">notify-passive</strong></span></p>
2894                         </td>
2895 <td>
2896                           <p>
2897                             no
2898                           </p>
2899                         </td>
2900 <td>
2901                           <p>
2902                             no
2903                           </p>
2904                         </td>
2905 <td>
2906                           <p>
2907                             yes
2908                           </p>
2909                         </td>
2910 </tr>
2911 </tbody>
2912 </table></div>
2913 <p>
2914                   Note that normal NOTIFY processing is not affected by
2915                   <span><strong class="command">dialup</strong></span>.
2916                 </p>
2917 </dd>
2918 <dt><span class="term"><span><strong class="command">fake-iquery</strong></span></span></dt>
2919 <dd><p>
2920                   In <acronym class="acronym">BIND</acronym> 8, this option
2921                   enabled simulating the obsolete DNS query type
2922                   IQUERY. <acronym class="acronym">BIND</acronym> 9 never does
2923                   IQUERY simulation.
2924                 </p></dd>
2925 <dt><span class="term"><span><strong class="command">fetch-glue</strong></span></span></dt>
2926 <dd><p>
2927                   This option is obsolete.
2928                   In BIND 8, <strong class="userinput"><code>fetch-glue yes</code></strong>
2929                   caused the server to attempt to fetch glue resource records
2930                   it
2931                   didn't have when constructing the additional
2932                   data section of a response.  This is now considered a bad
2933                   idea
2934                   and BIND 9 never does it.
2935                 </p></dd>
2936 <dt><span class="term"><span><strong class="command">flush-zones-on-shutdown</strong></span></span></dt>
2937 <dd><p>
2938                   When the nameserver exits due receiving SIGTERM,
2939                   flush or do not flush any pending zone writes.  The default
2940                   is
2941                   <span><strong class="command">flush-zones-on-shutdown</strong></span> <strong class="userinput"><code>no</code></strong>.
2942                 </p></dd>
2943 <dt><span class="term"><span><strong class="command">has-old-clients</strong></span></span></dt>
2944 <dd><p>
2945                   This option was incorrectly implemented
2946                   in <acronym class="acronym">BIND</acronym> 8, and is ignored by <acronym class="acronym">BIND</acronym> 9.
2947                   To achieve the intended effect
2948                   of
2949                   <span><strong class="command">has-old-clients</strong></span> <strong class="userinput"><code>yes</code></strong>, specify
2950                   the two separate options <span><strong class="command">auth-nxdomain</strong></span> <strong class="userinput"><code>yes</code></strong>
2951                   and <span><strong class="command">rfc2308-type1</strong></span> <strong class="userinput"><code>no</code></strong> instead.
2952                 </p></dd>
2953 <dt><span class="term"><span><strong class="command">host-statistics</strong></span></span></dt>
2954 <dd><p>
2955                   In BIND 8, this enables keeping of
2956                   statistics for every host that the name server interacts
2957                   with.
2958                   Not implemented in BIND 9.
2959                 </p></dd>
2960 <dt><span class="term"><span><strong class="command">maintain-ixfr-base</strong></span></span></dt>
2961 <dd><p>
2962                   <span class="emphasis"><em>This option is obsolete</em></span>.
2963                   It was used in <acronym class="acronym">BIND</acronym> 8 to
2964                   determine whether a transaction log was
2965                   kept for Incremental Zone Transfer. <acronym class="acronym">BIND</acronym> 9 maintains a transaction
2966                   log whenever possible.  If you need to disable outgoing
2967                   incremental zone
2968                   transfers, use <span><strong class="command">provide-ixfr</strong></span> <strong class="userinput"><code>no</code></strong>.
2969                 </p></dd>
2970 <dt><span class="term"><span><strong class="command">minimal-responses</strong></span></span></dt>
2971 <dd><p>
2972                   If <strong class="userinput"><code>yes</code></strong>, then when generating
2973                   responses the server will only add records to the authority
2974                   and additional data sections when they are required (e.g.
2975                   delegations, negative responses).  This may improve the
2976                   performance of the server.
2977                   The default is <strong class="userinput"><code>no</code></strong>.
2978                 </p></dd>
2979 <dt><span class="term"><span><strong class="command">multiple-cnames</strong></span></span></dt>
2980 <dd><p>
2981                   This option was used in <acronym class="acronym">BIND</acronym> 8 to allow
2982                   a domain name to have multiple CNAME records in violation of
2983                   the DNS standards.  <acronym class="acronym">BIND</acronym> 9.2 onwards
2984                   always strictly enforces the CNAME rules both in master
2985                   files and dynamic updates.
2986                 </p></dd>
2987 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
2988 <dd>
2989 <p>
2990                   If <strong class="userinput"><code>yes</code></strong> (the default),
2991                   DNS NOTIFY messages are sent when a zone the server is
2992                   authoritative for
2993                   changes, see <a href="Bv9ARM.ch04.html#notify" title="Notify">the section called &#8220;Notify&#8221;</a>.  The messages are
2994                   sent to the
2995                   servers listed in the zone's NS records (except the master
2996                   server identified
2997                   in the SOA MNAME field), and to any servers listed in the
2998                   <span><strong class="command">also-notify</strong></span> option.
2999                 </p>
3000 <p>
3001                   If <strong class="userinput"><code>master-only</code></strong>, notifies are only
3002                   sent
3003                   for master zones.
3004                   If <strong class="userinput"><code>explicit</code></strong>, notifies are sent only
3005                   to
3006                   servers explicitly listed using <span><strong class="command">also-notify</strong></span>.
3007                   If <strong class="userinput"><code>no</code></strong>, no notifies are sent.
3008                 </p>
3009 <p>
3010                   The <span><strong class="command">notify</strong></span> option may also be
3011                   specified in the <span><strong class="command">zone</strong></span>
3012                   statement,
3013                   in which case it overrides the <span><strong class="command">options notify</strong></span> statement.
3014                   It would only be necessary to turn off this option if it
3015                   caused slaves
3016                   to crash.
3017                 </p>
3018 </dd>
3019 <dt><span class="term"><span><strong class="command">notify-to-soa</strong></span></span></dt>
3020 <dd><p>
3021                   If <strong class="userinput"><code>yes</code></strong> do not check the nameservers
3022                   in the NS RRset against the SOA MNAME.  Normally a NOTIFY
3023                   message is not sent to the SOA MNAME (SOA ORIGIN) as it is
3024                   supposed to contain the name of the ultimate master.
3025                   Sometimes, however, a slave is listed as the SOA MNAME in
3026                   hidden master configurations and in that case you would
3027                   want the ultimate master to still send NOTIFY messages to
3028                   all the nameservers listed in the NS RRset.
3029                 </p></dd>
3030 <dt><span class="term"><span><strong class="command">recursion</strong></span></span></dt>
3031 <dd><p>
3032                   If <strong class="userinput"><code>yes</code></strong>, and a
3033                   DNS query requests recursion, then the server will attempt
3034                   to do
3035                   all the work required to answer the query. If recursion is
3036                   off
3037                   and the server does not already know the answer, it will
3038                   return a
3039                   referral response. The default is
3040                   <strong class="userinput"><code>yes</code></strong>.
3041                   Note that setting <span><strong class="command">recursion no</strong></span> does not prevent
3042                   clients from getting data from the server's cache; it only
3043                   prevents new data from being cached as an effect of client
3044                   queries.
3045                   Caching may still occur as an effect the server's internal
3046                   operation, such as NOTIFY address lookups.
3047                   See also <span><strong class="command">fetch-glue</strong></span> above.
3048                 </p></dd>
3049 <dt><span class="term"><span><strong class="command">rfc2308-type1</strong></span></span></dt>
3050 <dd>
3051 <p>
3052                   Setting this to <strong class="userinput"><code>yes</code></strong> will
3053                   cause the server to send NS records along with the SOA
3054                   record for negative
3055                   answers. The default is <strong class="userinput"><code>no</code></strong>.
3056                 </p>
3057 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3058 <h3 class="title">Note</h3>
3059 <p>
3060                     Not yet implemented in <acronym class="acronym">BIND</acronym>
3061                     9.
3062                   </p>
3063 </div>
3064 </dd>
3065 <dt><span class="term"><span><strong class="command">use-id-pool</strong></span></span></dt>
3066 <dd><p>
3067                   <span class="emphasis"><em>This option is obsolete</em></span>.
3068                   <acronym class="acronym">BIND</acronym> 9 always allocates query
3069                   IDs from a pool.
3070                 </p></dd>
3071 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
3072 <dd><p>
3073                   If <strong class="userinput"><code>yes</code></strong>, the server will collect
3074                   statistical data on all zones (unless specifically turned
3075                   off
3076                   on a per-zone basis by specifying <span><strong class="command">zone-statistics no</strong></span>
3077                   in the <span><strong class="command">zone</strong></span> statement).
3078                   The default is <strong class="userinput"><code>no</code></strong>.
3079                   These statistics may be accessed
3080                   using <span><strong class="command">rndc stats</strong></span>, which will
3081                   dump them to the file listed
3082                   in the <span><strong class="command">statistics-file</strong></span>.  See
3083                   also <a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
3084                 </p></dd>
3085 <dt><span class="term"><span><strong class="command">use-ixfr</strong></span></span></dt>
3086 <dd><p>
3087                   <span class="emphasis"><em>This option is obsolete</em></span>.
3088                   If you need to disable IXFR to a particular server or
3089                   servers, see
3090                   the information on the <span><strong class="command">provide-ixfr</strong></span> option
3091                   in <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3092             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3093             Usage&#8221;</a>.
3094                   See also
3095                   <a href="Bv9ARM.ch04.html#incremental_zone_transfers" title="Incremental Zone Transfers (IXFR)">the section called &#8220;Incremental Zone Transfers (IXFR)&#8221;</a>.
3096                 </p></dd>
3097 <dt><span class="term"><span><strong class="command">provide-ixfr</strong></span></span></dt>
3098 <dd><p>
3099                   See the description of
3100                   <span><strong class="command">provide-ixfr</strong></span> in
3101                   <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3102             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3103             Usage&#8221;</a>.
3104                 </p></dd>
3105 <dt><span class="term"><span><strong class="command">request-ixfr</strong></span></span></dt>
3106 <dd><p>
3107                   See the description of
3108                   <span><strong class="command">request-ixfr</strong></span> in
3109                   <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3110             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3111             Usage&#8221;</a>.
3112                 </p></dd>
3113 <dt><span class="term"><span><strong class="command">treat-cr-as-space</strong></span></span></dt>
3114 <dd><p>
3115                   This option was used in <acronym class="acronym">BIND</acronym>
3116                   8 to make
3117                   the server treat carriage return ("<span><strong class="command">\r</strong></span>") characters the same way
3118                   as a space or tab character,
3119                   to facilitate loading of zone files on a UNIX system that
3120                   were generated
3121                   on an NT or DOS machine. In <acronym class="acronym">BIND</acronym> 9, both UNIX "<span><strong class="command">\n</strong></span>"
3122                   and NT/DOS "<span><strong class="command">\r\n</strong></span>" newlines
3123                   are always accepted,
3124                   and the option is ignored.
3125                 </p></dd>
3126 <dt>
3127 <span class="term"><span><strong class="command">additional-from-auth</strong></span>, </span><span class="term"><span><strong class="command">additional-from-cache</strong></span></span>
3128 </dt>
3129 <dd>
3130 <p>
3131                   These options control the behavior of an authoritative
3132                   server when
3133                   answering queries which have additional data, or when
3134                   following CNAME
3135                   and DNAME chains.
3136                 </p>
3137 <p>
3138                   When both of these options are set to <strong class="userinput"><code>yes</code></strong>
3139                   (the default) and a
3140                   query is being answered from authoritative data (a zone
3141                   configured into the server), the additional data section of
3142                   the
3143                   reply will be filled in using data from other authoritative
3144                   zones
3145                   and from the cache.  In some situations this is undesirable,
3146                   such
3147                   as when there is concern over the correctness of the cache,
3148                   or
3149                   in servers where slave zones may be added and modified by
3150                   untrusted third parties.  Also, avoiding
3151                   the search for this additional data will speed up server
3152                   operations
3153                   at the possible expense of additional queries to resolve
3154                   what would
3155                   otherwise be provided in the additional section.
3156                 </p>
3157 <p>
3158                   For example, if a query asks for an MX record for host <code class="literal">foo.example.com</code>,
3159                   and the record found is "<code class="literal">MX 10 mail.example.net</code>", normally the address
3160                   records (A and AAAA) for <code class="literal">mail.example.net</code> will be provided as well,
3161                   if known, even though they are not in the example.com zone.
3162                   Setting these options to <span><strong class="command">no</strong></span>
3163                   disables this behavior and makes
3164                   the server only search for additional data in the zone it
3165                   answers from.
3166                 </p>
3167 <p>
3168                   These options are intended for use in authoritative-only
3169                   servers, or in authoritative-only views.  Attempts to set
3170                   them to <span><strong class="command">no</strong></span> without also
3171                   specifying
3172                   <span><strong class="command">recursion no</strong></span> will cause the
3173                   server to
3174                   ignore the options and log a warning message.
3175                 </p>
3176 <p>
3177                   Specifying <span><strong class="command">additional-from-cache no</strong></span> actually
3178                   disables the use of the cache not only for additional data
3179                   lookups
3180                   but also when looking up the answer.  This is usually the
3181                   desired
3182                   behavior in an authoritative-only server where the
3183                   correctness of
3184                   the cached data is an issue.
3185                 </p>
3186 <p>
3187                   When a name server is non-recursively queried for a name
3188                   that is not
3189                   below the apex of any served zone, it normally answers with
3190                   an
3191                   "upwards referral" to the root servers or the servers of
3192                   some other
3193                   known parent of the query name.  Since the data in an
3194                   upwards referral
3195                   comes from the cache, the server will not be able to provide
3196                   upwards
3197                   referrals when <span><strong class="command">additional-from-cache no</strong></span>
3198                   has been specified.  Instead, it will respond to such
3199                   queries
3200                   with REFUSED.  This should not cause any problems since
3201                   upwards referrals are not required for the resolution
3202                   process.
3203                 </p>
3204 </dd>
3205 <dt><span class="term"><span><strong class="command">match-mapped-addresses</strong></span></span></dt>
3206 <dd>
3207 <p>
3208                   If <strong class="userinput"><code>yes</code></strong>, then an
3209                   IPv4-mapped IPv6 address will match any address match
3210                   list entries that match the corresponding IPv4 address.
3211                 </p>
3212 <p>
3213                   This option was introduced to work around a kernel quirk
3214                   in some operating systems that causes IPv4 TCP
3215                   connections, such as zone transfers, to be accepted on an
3216                   IPv6 socket using mapped addresses.  This caused address
3217                   match lists designed for IPv4 to fail to match.  However,
3218                   <span><strong class="command">named</strong></span> now solves this problem
3219                   internally.  The use of this option is discouraged.
3220                 </p>
3221 </dd>
3222 <dt><span class="term"><span><strong class="command">filter-aaaa-on-v4</strong></span></span></dt>
3223 <dd>
3224 <p>
3225                   This option is only available when
3226                   <acronym class="acronym">BIND</acronym> 9 is compiled with the
3227                   <strong class="userinput"><code>--enable-filter-aaaa</code></strong> option on the
3228                   "configure" command line.  It is intended to help the
3229                   transition from IPv4 to IPv6 by not giving IPv6 addresses
3230                   to DNS clients unless they have connections to the IPv6
3231                   Internet.  This is not recommended unless absolutely
3232                   necessary.  The default is <strong class="userinput"><code>no</code></strong>.
3233                   The <span><strong class="command">filter-aaaa-on-v4</strong></span> option
3234                   may also be specified in <span><strong class="command">view</strong></span> statements
3235                   to override the global <span><strong class="command">filter-aaaa-on-v4</strong></span>
3236                   option.
3237                 </p>
3238 <p>
3239                   If <strong class="userinput"><code>yes</code></strong>,
3240                   the DNS client is at an IPv4 address,
3241                   and if the response does not include DNSSEC signatures,
3242                   then all AAAA records are deleted from the response.
3243                   This filtering applies to all responses and not only
3244                   authoritative responses.
3245                 </p>
3246 <p>
3247                   If <strong class="userinput"><code>break-dnssec</code></strong>,
3248                   then AAAA records are deleted even when dnssec is enabled.
3249                   As suggested by the name, this makes the response not verify,
3250                   because the DNSSEC protocol is designed detect deletions.
3251                 </p>
3252 <p>
3253                   This mechanism can erroneously cause other servers to
3254                   not give AAAA records to their clients.
3255                   A recursing server with both IPv6 and IPv4 network connections
3256                   that queries an authoritative server using this mechanism
3257                   via IPv4 will be denied AAAA records even if its client is
3258                   using IPv6.
3259                 </p>
3260 <p>
3261                   This mechanism is applied to authoritative as well as
3262                   non-authoritative records.
3263                   A client using IPv4 that is not allowed recursion can
3264                   erroneously be given AAAA records because the server is not
3265                   allowed to check for A records.
3266                 </p>
3267 <p>
3268                   Some AAAA records are given to IPv4 clients in glue records.
3269                   IPv4 clients that are servers can then erroneously
3270                   answer requests for AAAA records received via IPv4.
3271                 </p>
3272 </dd>
3273 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
3274 <dd>
3275 <p>
3276                   When <strong class="userinput"><code>yes</code></strong> and the server loads a new version of a master
3277                   zone from its zone file or receives a new version of a slave
3278                   file by a non-incremental zone transfer, it will compare
3279                   the new version to the previous one and calculate a set
3280                   of differences.  The differences are then logged in the
3281                   zone's journal file such that the changes can be transmitted
3282                   to downstream slaves as an incremental zone transfer.
3283                 </p>
3284 <p>
3285                   By allowing incremental zone transfers to be used for
3286                   non-dynamic zones, this option saves bandwidth at the
3287                   expense of increased CPU and memory consumption at the
3288                   master.
3289                   In particular, if the new version of a zone is completely
3290                   different from the previous one, the set of differences
3291                   will be of a size comparable to the combined size of the
3292                   old and new zone version, and the server will need to
3293                   temporarily allocate memory to hold this complete
3294                   difference set.
3295                 </p>
3296 <p><span><strong class="command">ixfr-from-differences</strong></span>
3297                   also accepts <span><strong class="command">master</strong></span> and
3298                   <span><strong class="command">slave</strong></span> at the view and options
3299                   levels which causes
3300                   <span><strong class="command">ixfr-from-differences</strong></span> to be enabled for
3301                   all <span><strong class="command">master</strong></span> or
3302                   <span><strong class="command">slave</strong></span> zones respectively.
3303                   It is off by default.
3304                 </p>
3305 </dd>
3306 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
3307 <dd><p>
3308                   This should be set when you have multiple masters for a zone
3309                   and the
3310                   addresses refer to different machines.  If <strong class="userinput"><code>yes</code></strong>, <span><strong class="command">named</strong></span> will
3311                   not log
3312                   when the serial number on the master is less than what <span><strong class="command">named</strong></span>
3313                   currently
3314                   has.  The default is <strong class="userinput"><code>no</code></strong>.
3315                 </p></dd>
3316 <dt><span class="term"><span><strong class="command">dnssec-enable</strong></span></span></dt>
3317 <dd><p>
3318                   Enable DNSSEC support in <span><strong class="command">named</strong></span>.  Unless set to <strong class="userinput"><code>yes</code></strong>,
3319                   <span><strong class="command">named</strong></span> behaves as if it does not support DNSSEC.
3320                   The default is <strong class="userinput"><code>yes</code></strong>.
3321                 </p></dd>
3322 <dt><span class="term"><span><strong class="command">dnssec-validation</strong></span></span></dt>
3323 <dd><p>
3324                   Enable DNSSEC validation in <span><strong class="command">named</strong></span>.
3325                   Note <span><strong class="command">dnssec-enable</strong></span> also needs to be
3326                   set to <strong class="userinput"><code>yes</code></strong> to be effective.
3327                   The default is <strong class="userinput"><code>yes</code></strong>.
3328                 </p></dd>
3329 <dt><span class="term"><span><strong class="command">dnssec-accept-expired</strong></span></span></dt>
3330 <dd><p>
3331                   Accept expired signatures when verifying DNSSEC signatures.
3332                   The default is <strong class="userinput"><code>no</code></strong>.
3333                   Setting this option to <strong class="userinput"><code>yes</code></strong>
3334                   leaves <span><strong class="command">named</strong></span> vulnerable to
3335                   replay attacks.
3336                 </p></dd>
3337 <dt><span class="term"><span><strong class="command">querylog</strong></span></span></dt>
3338 <dd><p>
3339                   Specify whether query logging should be started when <span><strong class="command">named</strong></span>
3340                   starts.
3341                   If <span><strong class="command">querylog</strong></span> is not specified,
3342                   then the query logging
3343                   is determined by the presence of the logging category <span><strong class="command">queries</strong></span>.
3344                 </p></dd>
3345 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
3346 <dd>
3347 <p>
3348                   This option is used to restrict the character set and syntax
3349                   of
3350                   certain domain names in master files and/or DNS responses
3351                   received
3352                   from the network.  The default varies according to usage
3353                   area.  For
3354                   <span><strong class="command">master</strong></span> zones the default is <span><strong class="command">fail</strong></span>.
3355                   For <span><strong class="command">slave</strong></span> zones the default
3356                   is <span><strong class="command">warn</strong></span>.
3357                   For answers received from the network (<span><strong class="command">response</strong></span>)
3358                   the default is <span><strong class="command">ignore</strong></span>.
3359                 </p>
3360 <p>
3361                   The rules for legal hostnames and mail domains are derived
3362                   from RFC 952 and RFC 821 as modified by RFC 1123.
3363                 </p>
3364 <p><span><strong class="command">check-names</strong></span>
3365                   applies to the owner names of A, AAAA and MX records.
3366                   It also applies to the domain names in the RDATA of NS, SOA,
3367                   MX, and SRV records.
3368                   It also applies to the RDATA of PTR records where the owner
3369                   name indicated that it is a reverse lookup of a hostname
3370                   (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, or IP6.INT).
3371                 </p>
3372 </dd>
3373 <dt><span class="term"><span><strong class="command">check-dup-records</strong></span></span></dt>
3374 <dd><p>
3375                   Check master zones for records that are treated as different
3376                   by DNSSEC but are semantically equal in plain DNS.  The
3377                   default is to <span><strong class="command">warn</strong></span>.  Other possible
3378                   values are <span><strong class="command">fail</strong></span> and
3379                   <span><strong class="command">ignore</strong></span>.
3380                 </p></dd>
3381 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
3382 <dd><p>
3383                   Check whether the MX record appears to refer to a IP address.
3384                   The default is to <span><strong class="command">warn</strong></span>.  Other possible
3385                   values are <span><strong class="command">fail</strong></span> and
3386                   <span><strong class="command">ignore</strong></span>.
3387                 </p></dd>
3388 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
3389 <dd><p>
3390                   Check whether the MX record appears to refer to a IP address.
3391                   The default is to <span><strong class="command">warn</strong></span>.  Other possible
3392                   values are <span><strong class="command">fail</strong></span> and
3393                   <span><strong class="command">ignore</strong></span>.
3394                 </p></dd>
3395 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
3396 <dd><p>
3397                   This option is used to check for non-terminal wildcards.
3398                   The use of non-terminal wildcards is almost always as a
3399                   result of a failure
3400                   to understand the wildcard matching algorithm (RFC 1034).
3401                   This option
3402                   affects master zones.  The default (<span><strong class="command">yes</strong></span>) is to check
3403                   for non-terminal wildcards and issue a warning.
3404                 </p></dd>
3405 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
3406 <dd><p>
3407                   Perform post load zone integrity checks on master
3408                   zones.  This checks that MX and SRV records refer
3409                   to address (A or AAAA) records and that glue
3410                   address records exist for delegated zones.  For
3411                   MX and SRV records only in-zone hostnames are
3412                   checked (for out-of-zone hostnames use
3413                   <span><strong class="command">named-checkzone</strong></span>).
3414                   For NS records only names below top of zone are
3415                   checked (for out-of-zone names and glue consistency
3416                   checks use <span><strong class="command">named-checkzone</strong></span>).
3417                   The default is <span><strong class="command">yes</strong></span>.
3418                 </p></dd>
3419 <dt><span class="term"><span><strong class="command">check-mx-cname</strong></span></span></dt>
3420 <dd><p>
3421                   If <span><strong class="command">check-integrity</strong></span> is set then
3422                   fail, warn or ignore MX records that refer
3423                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
3424                 </p></dd>
3425 <dt><span class="term"><span><strong class="command">check-srv-cname</strong></span></span></dt>
3426 <dd><p>
3427                   If <span><strong class="command">check-integrity</strong></span> is set then
3428                   fail, warn or ignore SRV records that refer
3429                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
3430                 </p></dd>
3431 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
3432 <dd><p>
3433                   When performing integrity checks, also check that
3434                   sibling glue exists.  The default is <span><strong class="command">yes</strong></span>.
3435                 </p></dd>
3436 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
3437 <dd><p>
3438                   When returning authoritative negative responses to
3439                   SOA queries set the TTL of the SOA record returned in
3440                   the authority section to zero.
3441                   The default is <span><strong class="command">yes</strong></span>.
3442                 </p></dd>
3443 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl-cache</strong></span></span></dt>
3444 <dd><p>
3445                   When caching a negative response to a SOA query
3446                   set the TTL to zero.
3447                   The default is <span><strong class="command">no</strong></span>.
3448                 </p></dd>
3449 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
3450 <dd>
3451 <p>
3452                   When set to the default value of <code class="literal">yes</code>,
3453                   check the KSK bit in each key to determine how the key
3454                   should be used when generating RRSIGs for a secure zone.
3455                 </p>
3456 <p>
3457                   Ordinarily, zone-signing keys (that is, keys without the
3458                   KSK bit set) are used to sign the entire zone, while
3459                   key-signing keys (keys with the KSK bit set) are only
3460                   used to sign the DNSKEY RRset at the zone apex.
3461                   However, if this option is set to <code class="literal">no</code>,
3462                   then the KSK bit is ignored; KSKs are treated as if they
3463                   were ZSKs and are used to sign the entire zone.  This is
3464                   similar to the <span><strong class="command">dnssec-signzone -z</strong></span>
3465                   command line option.
3466                 </p>
3467 <p>
3468                   When this option is set to <code class="literal">yes</code>, there
3469                   must be at least two active keys for every algorithm
3470                   represented in the DNSKEY RRset: at least one KSK and one
3471                   ZSK per algorithm.  If there is any algorithm for which
3472                   this requirement is not met, this option will be ignored
3473                   for that algorithm.
3474                 </p>
3475 </dd>
3476 <dt><span class="term"><span><strong class="command">dnssec-dnskey-kskonly</strong></span></span></dt>
3477 <dd>
3478 <p>
3479                   When this option and <span><strong class="command">update-check-ksk</strong></span>
3480                   are both set to <code class="literal">yes</code>, only key-signing
3481                   keys (that is, keys with the KSK bit set) will be used
3482                   to sign the DNSKEY RRset at the zone apex.  Zone-signing
3483                   keys (keys without the KSK bit set) will be used to sign
3484                   the remainder of the zone, but not the DNSKEY RRset.
3485                   This is similar to the
3486                   <span><strong class="command">dnssec-signzone -x</strong></span> command line option.
3487                 </p>
3488 <p>
3489                   The default is <span><strong class="command">no</strong></span>.  If
3490                   <span><strong class="command">update-check-ksk</strong></span> is set to
3491                   <code class="literal">no</code>, this option is ignored.
3492                 </p>
3493 </dd>
3494 <dt><span class="term"><span><strong class="command">try-tcp-refresh</strong></span></span></dt>
3495 <dd><p>
3496                   Try to refresh the zone using TCP if UDP queries fail.
3497                   For BIND 8 compatibility, the default is
3498                   <span><strong class="command">yes</strong></span>.
3499                 </p></dd>
3500 <dt><span class="term"><span><strong class="command">dnssec-secure-to-insecure</strong></span></span></dt>
3501 <dd>
3502 <p>
3503                   Allow a dynamic zone to transition from secure to
3504                   insecure (i.e., signed to unsigned) by deleting all
3505                   of the DNSKEY records.  The default is <span><strong class="command">no</strong></span>.
3506                   If set to <span><strong class="command">yes</strong></span>, and if the DNSKEY RRset
3507                   at the zone apex is deleted, all RRSIG and NSEC records
3508                   will be removed from the zone as well.
3509                 </p>
3510 <p>
3511                   If the zone uses NSEC3, then it is also necessary to
3512                   delete the NSEC3PARAM RRset from the zone apex; this will
3513                   cause the removal of all corresponding NSEC3 records.
3514                   (It is expected that this requirement will be eliminated
3515                   in a future release.)
3516                 </p>
3517 <p>
3518                   Note that if a zone has been configured with
3519                   <span><strong class="command">auto-dnssec maintain</strong></span> and the
3520                   private keys remain accessible in the key repository,
3521                   then the zone will be automatically signed again the
3522                   next time <span><strong class="command">named</strong></span> is started.
3523                 </p>
3524 </dd>
3525 </dl></div>
3526 </div>
3527 <div class="sect3" lang="en">
3528 <div class="titlepage"><div><div><h4 class="title">
3529 <a name="id2582876"></a>Forwarding</h4></div></div></div>
3530 <p>
3531             The forwarding facility can be used to create a large site-wide
3532             cache on a few servers, reducing traffic over links to external
3533             name servers. It can also be used to allow queries by servers that
3534             do not have direct access to the Internet, but wish to look up
3535             exterior
3536             names anyway. Forwarding occurs only on those queries for which
3537             the server is not authoritative and does not have the answer in
3538             its cache.
3539           </p>
3540 <div class="variablelist"><dl>
3541 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
3542 <dd><p>
3543                   This option is only meaningful if the
3544                   forwarders list is not empty. A value of <code class="varname">first</code>,
3545                   the default, causes the server to query the forwarders
3546                   first &#8212; and
3547                   if that doesn't answer the question, the server will then
3548                   look for
3549                   the answer itself. If <code class="varname">only</code> is
3550                   specified, the
3551                   server will only query the forwarders.
3552                 </p></dd>
3553 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
3554 <dd><p>
3555                   Specifies the IP addresses to be used
3556                   for forwarding. The default is the empty list (no
3557                   forwarding).
3558                 </p></dd>
3559 </dl></div>
3560 <p>
3561             Forwarding can also be configured on a per-domain basis, allowing
3562             for the global forwarding options to be overridden in a variety
3563             of ways. You can set particular domains to use different
3564             forwarders,
3565             or have a different <span><strong class="command">forward only/first</strong></span> behavior,
3566             or not forward at all, see <a href="Bv9ARM.ch06.html#zone_statement_grammar" title="zone
3567             Statement Grammar">the section called &#8220;<span><strong class="command">zone</strong></span>
3568             Statement Grammar&#8221;</a>.
3569           </p>
3570 </div>
3571 <div class="sect3" lang="en">
3572 <div class="titlepage"><div><div><h4 class="title">
3573 <a name="id2582935"></a>Dual-stack Servers</h4></div></div></div>
3574 <p>
3575             Dual-stack servers are used as servers of last resort to work
3576             around
3577             problems in reachability due the lack of support for either IPv4
3578             or IPv6
3579             on the host machine.
3580           </p>
3581 <div class="variablelist"><dl>
3582 <dt><span class="term"><span><strong class="command">dual-stack-servers</strong></span></span></dt>
3583 <dd><p>
3584                   Specifies host names or addresses of machines with access to
3585                   both IPv4 and IPv6 transports. If a hostname is used, the
3586                   server must be able
3587                   to resolve the name using only the transport it has.  If the
3588                   machine is dual
3589                   stacked, then the <span><strong class="command">dual-stack-servers</strong></span> have no effect unless
3590                   access to a transport has been disabled on the command line
3591                   (e.g. <span><strong class="command">named -4</strong></span>).
3592                 </p></dd>
3593 </dl></div>
3594 </div>
3595 <div class="sect3" lang="en">
3596 <div class="titlepage"><div><div><h4 class="title">
3597 <a name="access_control"></a>Access Control</h4></div></div></div>
3598 <p>
3599             Access to the server can be restricted based on the IP address
3600             of the requesting system. See <a href="Bv9ARM.ch06.html#address_match_lists" title="Address Match Lists">the section called &#8220;Address Match Lists&#8221;</a> for
3601             details on how to specify IP address lists.
3602           </p>
3603 <div class="variablelist"><dl>
3604 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
3605 <dd><p>
3606                   Specifies which hosts are allowed to
3607                   notify this server, a slave, of zone changes in addition
3608                   to the zone masters.
3609                   <span><strong class="command">allow-notify</strong></span> may also be
3610                   specified in the
3611                   <span><strong class="command">zone</strong></span> statement, in which case
3612                   it overrides the
3613                   <span><strong class="command">options allow-notify</strong></span>
3614                   statement.  It is only meaningful
3615                   for a slave zone.  If not specified, the default is to
3616                   process notify messages
3617                   only from a zone's master.
3618                 </p></dd>
3619 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
3620 <dd>
3621 <p>
3622                   Specifies which hosts are allowed to ask ordinary
3623                   DNS questions. <span><strong class="command">allow-query</strong></span> may
3624                   also be specified in the <span><strong class="command">zone</strong></span>
3625                   statement, in which case it overrides the
3626                   <span><strong class="command">options allow-query</strong></span> statement.
3627                   If not specified, the default is to allow queries
3628                   from all hosts.
3629                 </p>
3630 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3631 <h3 class="title">Note</h3>
3632 <p>
3633                     <span><strong class="command">allow-query-cache</strong></span> is now
3634                     used to specify access to the cache.
3635                   </p>
3636 </div>
3637 </dd>
3638 <dt><span class="term"><span><strong class="command">allow-query-on</strong></span></span></dt>
3639 <dd>
3640 <p>
3641                   Specifies which local addresses can accept ordinary
3642                   DNS questions. This makes it possible, for instance,
3643                   to allow queries on internal-facing interfaces but
3644                   disallow them on external-facing ones, without
3645                   necessarily knowing the internal network's addresses.
3646                 </p>
3647 <p>
3648                   <span><strong class="command">allow-query-on</strong></span> may
3649                   also be specified in the <span><strong class="command">zone</strong></span>
3650                   statement, in which case it overrides the
3651                   <span><strong class="command">options allow-query-on</strong></span> statement.
3652                 </p>
3653 <p>
3654                   If not specified, the default is to allow queries
3655                   on all addresses.
3656                 </p>
3657 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3658 <h3 class="title">Note</h3>
3659 <p>
3660                     <span><strong class="command">allow-query-cache</strong></span> is
3661                     used to specify access to the cache.
3662                   </p>
3663 </div>
3664 </dd>
3665 <dt><span class="term"><span><strong class="command">allow-query-cache</strong></span></span></dt>
3666 <dd><p>
3667                   Specifies which hosts are allowed to get answers
3668                   from the cache.  If <span><strong class="command">allow-query-cache</strong></span>
3669                   is not set then <span><strong class="command">allow-recursion</strong></span>
3670                   is used if set, otherwise <span><strong class="command">allow-query</strong></span>
3671                   is used if set unless <span><strong class="command">recursion no;</strong></span> is
3672                   set in which case <span><strong class="command">none;</strong></span> is used,
3673                   otherwise the default (<span><strong class="command">localnets;</strong></span>
3674                   <span><strong class="command">localhost;</strong></span>) is used.
3675                 </p></dd>
3676 <dt><span class="term"><span><strong class="command">allow-query-cache-on</strong></span></span></dt>
3677 <dd><p>
3678                   Specifies which local addresses can give answers
3679                   from the cache.  If not specified, the default is
3680                   to allow cache queries on any address,
3681                   <span><strong class="command">localnets</strong></span> and
3682                   <span><strong class="command">localhost</strong></span>.
3683                 </p></dd>
3684 <dt><span class="term"><span><strong class="command">allow-recursion</strong></span></span></dt>
3685 <dd><p>
3686                   Specifies which hosts are allowed to make recursive
3687                   queries through this server. If
3688                   <span><strong class="command">allow-recursion</strong></span> is not set
3689                   then <span><strong class="command">allow-query-cache</strong></span> is
3690                   used if set, otherwise <span><strong class="command">allow-query</strong></span>
3691                   is used if set, otherwise the default
3692                   (<span><strong class="command">localnets;</strong></span>
3693                   <span><strong class="command">localhost;</strong></span>) is used.
3694                 </p></dd>
3695 <dt><span class="term"><span><strong class="command">allow-recursion-on</strong></span></span></dt>
3696 <dd><p>
3697                   Specifies which local addresses can accept recursive
3698                   queries.  If not specified, the default is to allow
3699                   recursive queries on all addresses.
3700                 </p></dd>
3701 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
3702 <dd><p>
3703                   Specifies which hosts are allowed to
3704                   submit Dynamic DNS updates for master zones. The default is
3705                   to deny
3706                   updates from all hosts.  Note that allowing updates based
3707                   on the requestor's IP address is insecure; see
3708                   <a href="Bv9ARM.ch07.html#dynamic_update_security" title="Dynamic Update Security">the section called &#8220;Dynamic Update Security&#8221;</a> for details.
3709                 </p></dd>
3710 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
3711 <dd>
3712 <p>
3713                   Specifies which hosts are allowed to
3714                   submit Dynamic DNS updates to slave zones to be forwarded to
3715                   the
3716                   master.  The default is <strong class="userinput"><code>{ none; }</code></strong>,
3717                   which
3718                   means that no update forwarding will be performed.  To
3719                   enable
3720                   update forwarding, specify
3721                   <strong class="userinput"><code>allow-update-forwarding { any; };</code></strong>.
3722                   Specifying values other than <strong class="userinput"><code>{ none; }</code></strong> or
3723                   <strong class="userinput"><code>{ any; }</code></strong> is usually
3724                   counterproductive, since
3725                   the responsibility for update access control should rest
3726                   with the
3727                   master server, not the slaves.
3728                 </p>
3729 <p>
3730                   Note that enabling the update forwarding feature on a slave
3731                   server
3732                   may expose master servers relying on insecure IP address
3733                   based
3734                   access control to attacks; see <a href="Bv9ARM.ch07.html#dynamic_update_security" title="Dynamic Update Security">the section called &#8220;Dynamic Update Security&#8221;</a>
3735                   for more details.
3736                 </p>
3737 </dd>
3738 <dt><span class="term"><span><strong class="command">allow-v6-synthesis</strong></span></span></dt>
3739 <dd><p>
3740                   This option was introduced for the smooth transition from
3741                   AAAA
3742                   to A6 and from "nibble labels" to binary labels.
3743                   However, since both A6 and binary labels were then
3744                   deprecated,
3745                   this option was also deprecated.
3746                   It is now ignored with some warning messages.
3747                 </p></dd>
3748 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
3749 <dd><p>
3750                   Specifies which hosts are allowed to
3751                   receive zone transfers from the server. <span><strong class="command">allow-transfer</strong></span> may
3752                   also be specified in the <span><strong class="command">zone</strong></span>
3753                   statement, in which
3754                   case it overrides the <span><strong class="command">options allow-transfer</strong></span> statement.
3755                   If not specified, the default is to allow transfers to all
3756                   hosts.
3757                 </p></dd>
3758 <dt><span class="term"><span><strong class="command">blackhole</strong></span></span></dt>
3759 <dd><p>
3760                   Specifies a list of addresses that the
3761                   server will not accept queries from or use to resolve a
3762                   query. Queries
3763                   from these addresses will not be responded to. The default
3764                   is <strong class="userinput"><code>none</code></strong>.
3765                 </p></dd>
3766 </dl></div>
3767 </div>
3768 <div class="sect3" lang="en">
3769 <div class="titlepage"><div><div><h4 class="title">
3770 <a name="id2583441"></a>Interfaces</h4></div></div></div>
3771 <p>
3772             The interfaces and ports that the server will answer queries
3773             from may be specified using the <span><strong class="command">listen-on</strong></span> option. <span><strong class="command">listen-on</strong></span> takes
3774             an optional port and an <code class="varname">address_match_list</code>.
3775             The server will listen on all interfaces allowed by the address
3776             match list. If a port is not specified, port 53 will be used.
3777           </p>
3778 <p>
3779             Multiple <span><strong class="command">listen-on</strong></span> statements are
3780             allowed.
3781             For example,
3782           </p>
3783 <pre class="programlisting">listen-on { 5.6.7.8; };
3784 listen-on port 1234 { !1.2.3.4; 1.2/16; };
3785 </pre>
3786 <p>
3787             will enable the name server on port 53 for the IP address
3788             5.6.7.8, and on port 1234 of an address on the machine in net
3789             1.2 that is not 1.2.3.4.
3790           </p>
3791 <p>
3792             If no <span><strong class="command">listen-on</strong></span> is specified, the
3793             server will listen on port 53 on all IPv4 interfaces.
3794           </p>
3795 <p>
3796             The <span><strong class="command">listen-on-v6</strong></span> option is used to
3797             specify the interfaces and the ports on which the server will
3798             listen
3799             for incoming queries sent using IPv6.
3800           </p>
3801 <p>
3802             When </p>
3803 <pre class="programlisting">{ any; }</pre>
3804 <p> is
3805             specified
3806             as the <code class="varname">address_match_list</code> for the
3807             <span><strong class="command">listen-on-v6</strong></span> option,
3808             the server does not bind a separate socket to each IPv6 interface
3809             address as it does for IPv4 if the operating system has enough API
3810             support for IPv6 (specifically if it conforms to RFC 3493 and RFC
3811             3542).
3812             Instead, it listens on the IPv6 wildcard address.
3813             If the system only has incomplete API support for IPv6, however,
3814             the behavior is the same as that for IPv4.
3815           </p>
3816 <p>
3817             A list of particular IPv6 addresses can also be specified, in
3818             which case
3819             the server listens on a separate socket for each specified
3820             address,
3821             regardless of whether the desired API is supported by the system.
3822           </p>
3823 <p>
3824             Multiple <span><strong class="command">listen-on-v6</strong></span> options can
3825             be used.
3826             For example,
3827           </p>
3828 <pre class="programlisting">listen-on-v6 { any; };
3829 listen-on-v6 port 1234 { !2001:db8::/32; any; };
3830 </pre>
3831 <p>
3832             will enable the name server on port 53 for any IPv6 addresses
3833             (with a single wildcard socket),
3834             and on port 1234 of IPv6 addresses that is not in the prefix
3835             2001:db8::/32 (with separate sockets for each matched address.)
3836           </p>
3837 <p>
3838             To make the server not listen on any IPv6 address, use
3839           </p>
3840 <pre class="programlisting">listen-on-v6 { none; };
3841 </pre>
3842 <p>
3843             If no <span><strong class="command">listen-on-v6</strong></span> option is
3844             specified, the server will not listen on any IPv6 address
3845             unless <span><strong class="command">-6</strong></span> is specified when <span><strong class="command">named</strong></span> is
3846             invoked.  If <span><strong class="command">-6</strong></span> is specified then
3847             <span><strong class="command">named</strong></span> will listen on port 53 on all IPv6 interfaces by default.
3848           </p>
3849 </div>
3850 <div class="sect3" lang="en">
3851 <div class="titlepage"><div><div><h4 class="title">
3852 <a name="query_address"></a>Query Address</h4></div></div></div>
3853 <p>
3854             If the server doesn't know the answer to a question, it will
3855             query other name servers. <span><strong class="command">query-source</strong></span> specifies
3856             the address and port used for such queries. For queries sent over
3857             IPv6, there is a separate <span><strong class="command">query-source-v6</strong></span> option.
3858             If <span><strong class="command">address</strong></span> is <span><strong class="command">*</strong></span> (asterisk) or is omitted,
3859             a wildcard IP address (<span><strong class="command">INADDR_ANY</strong></span>)
3860             will be used.
3861           </p>
3862 <p>
3863             If <span><strong class="command">port</strong></span> is <span><strong class="command">*</strong></span> or is omitted,
3864             a random port number from a pre-configured
3865             range is picked up and will be used for each query.
3866             The port range(s) is that specified in
3867             the <span><strong class="command">use-v4-udp-ports</strong></span> (for IPv4)
3868             and <span><strong class="command">use-v6-udp-ports</strong></span> (for IPv6)
3869             options, excluding the ranges specified in
3870             the <span><strong class="command">avoid-v4-udp-ports</strong></span>
3871             and <span><strong class="command">avoid-v6-udp-ports</strong></span> options, respectively.
3872           </p>
3873 <p>
3874             The defaults of the <span><strong class="command">query-source</strong></span> and
3875             <span><strong class="command">query-source-v6</strong></span> options
3876             are:
3877           </p>
3878 <pre class="programlisting">query-source address * port *;
3879 query-source-v6 address * port *;
3880 </pre>
3881 <p>
3882             If <span><strong class="command">use-v4-udp-ports</strong></span> or
3883             <span><strong class="command">use-v6-udp-ports</strong></span> is unspecified,
3884             <span><strong class="command">named</strong></span> will check if the operating
3885             system provides a programming interface to retrieve the
3886             system's default range for ephemeral ports.
3887             If such an interface is available,
3888             <span><strong class="command">named</strong></span> will use the corresponding system
3889             default range; otherwise, it will use its own defaults:
3890          </p>
3891 <pre class="programlisting">use-v4-udp-ports { range 1024 65535; };
3892 use-v6-udp-ports { range 1024 65535; };
3893 </pre>
3894 <p>
3895             Note: make sure the ranges be sufficiently large for
3896             security.  A desirable size depends on various parameters,
3897             but we generally recommend it contain at least 16384 ports
3898             (14 bits of entropy).
3899             Note also that the system's default range when used may be
3900             too small for this purpose, and that the range may even be
3901             changed while <span><strong class="command">named</strong></span> is running; the new
3902             range will automatically be applied when <span><strong class="command">named</strong></span>
3903             is reloaded.
3904             It is encouraged to
3905             configure <span><strong class="command">use-v4-udp-ports</strong></span> and
3906             <span><strong class="command">use-v6-udp-ports</strong></span> explicitly so that the
3907             ranges are sufficiently large and are reasonably
3908             independent from the ranges used by other applications.
3909           </p>
3910 <p>
3911             Note: the operational configuration
3912             where <span><strong class="command">named</strong></span> runs may prohibit the use
3913             of some ports.  For example, UNIX systems will not allow
3914             <span><strong class="command">named</strong></span> running without a root privilege
3915             to use ports less than 1024.
3916             If such ports are included in the specified (or detected)
3917             set of query ports, the corresponding query attempts will
3918             fail, resulting in resolution failures or delay.
3919             It is therefore important to configure the set of ports
3920             that can be safely used in the expected operational environment.
3921           </p>
3922 <p>
3923             The defaults of the <span><strong class="command">avoid-v4-udp-ports</strong></span> and
3924             <span><strong class="command">avoid-v6-udp-ports</strong></span> options
3925             are:
3926           </p>
3927 <pre class="programlisting">avoid-v4-udp-ports {};
3928 avoid-v6-udp-ports {};
3929 </pre>
3930 <p>
3931             Note: BIND 9.5.0 introduced
3932             the <span><strong class="command">use-queryport-pool</strong></span>
3933             option to support a pool of such random ports, but this
3934             option is now obsolete because reusing the same ports in
3935             the pool may not be sufficiently secure.
3936             For the same reason, it is generally strongly discouraged to
3937             specify a particular port for the
3938             <span><strong class="command">query-source</strong></span> or
3939             <span><strong class="command">query-source-v6</strong></span> options;
3940             it implicitly disables the use of randomized port numbers.
3941           </p>
3942 <div class="variablelist"><dl>
3943 <dt><span class="term"><span><strong class="command">use-queryport-pool</strong></span></span></dt>
3944 <dd><p>
3945                   This option is obsolete.
3946                 </p></dd>
3947 <dt><span class="term"><span><strong class="command">queryport-pool-ports</strong></span></span></dt>
3948 <dd><p>
3949                   This option is obsolete.
3950                 </p></dd>
3951 <dt><span class="term"><span><strong class="command">queryport-pool-updateinterval</strong></span></span></dt>
3952 <dd><p>
3953                   This option is obsolete.
3954                 </p></dd>
3955 </dl></div>
3956 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3957 <h3 class="title">Note</h3>
3958 <p>
3959               The address specified in the <span><strong class="command">query-source</strong></span> option
3960               is used for both UDP and TCP queries, but the port applies only
3961               to UDP queries.  TCP queries always use a random
3962               unprivileged port.
3963             </p>
3964 </div>
3965 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3966 <h3 class="title">Note</h3>
3967 <p>
3968               Solaris 2.5.1 and earlier does not support setting the source
3969               address for TCP sockets.
3970             </p>
3971 </div>
3972 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3973 <h3 class="title">Note</h3>
3974 <p>
3975               See also <span><strong class="command">transfer-source</strong></span> and
3976               <span><strong class="command">notify-source</strong></span>.
3977             </p>
3978 </div>
3979 </div>
3980 <div class="sect3" lang="en">
3981 <div class="titlepage"><div><div><h4 class="title">
3982 <a name="zone_transfers"></a>Zone Transfers</h4></div></div></div>
3983 <p>
3984             <acronym class="acronym">BIND</acronym> has mechanisms in place to
3985             facilitate zone transfers
3986             and set limits on the amount of load that transfers place on the
3987             system. The following options apply to zone transfers.
3988           </p>
3989 <div class="variablelist"><dl>
3990 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
3991 <dd><p>
3992                   Defines a global list of IP addresses of name servers
3993                   that are also sent NOTIFY messages whenever a fresh copy of
3994                   the
3995                   zone is loaded, in addition to the servers listed in the
3996                   zone's NS records.
3997                   This helps to ensure that copies of the zones will
3998                   quickly converge on stealth servers.
3999                   Optionally, a port may be specified with each
4000                   <span><strong class="command">also-notify</strong></span> address to send
4001                   the notify messages to a port other than the
4002                   default of 53.
4003                   If an <span><strong class="command">also-notify</strong></span> list
4004                   is given in a <span><strong class="command">zone</strong></span> statement,
4005                   it will override
4006                   the <span><strong class="command">options also-notify</strong></span>
4007                   statement. When a <span><strong class="command">zone notify</strong></span>
4008                   statement
4009                   is set to <span><strong class="command">no</strong></span>, the IP
4010                   addresses in the global <span><strong class="command">also-notify</strong></span> list will
4011                   not be sent NOTIFY messages for that zone. The default is
4012                   the empty
4013                   list (no global notification list).
4014                 </p></dd>
4015 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
4016 <dd><p>
4017                   Inbound zone transfers running longer than
4018                   this many minutes will be terminated. The default is 120
4019                   minutes
4020                   (2 hours).  The maximum value is 28 days (40320 minutes).
4021                 </p></dd>
4022 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
4023 <dd><p>
4024                   Inbound zone transfers making no progress
4025                   in this many minutes will be terminated. The default is 60
4026                   minutes
4027                   (1 hour).  The maximum value is 28 days (40320 minutes).
4028                 </p></dd>
4029 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
4030 <dd><p>
4031                   Outbound zone transfers running longer than
4032                   this many minutes will be terminated. The default is 120
4033                   minutes
4034                   (2 hours).  The maximum value is 28 days (40320 minutes).
4035                 </p></dd>
4036 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
4037 <dd><p>
4038                   Outbound zone transfers making no progress
4039                   in this many minutes will be terminated.  The default is 60
4040                   minutes (1
4041                   hour).  The maximum value is 28 days (40320 minutes).
4042                 </p></dd>
4043 <dt><span class="term"><span><strong class="command">serial-query-rate</strong></span></span></dt>
4044 <dd><p>
4045                   Slave servers will periodically query master servers
4046                   to find out if zone serial numbers have changed. Each such
4047                   query uses
4048                   a minute amount of the slave server's network bandwidth.  To
4049                   limit the
4050                   amount of bandwidth used, BIND 9 limits the rate at which
4051                   queries are
4052                   sent.  The value of the <span><strong class="command">serial-query-rate</strong></span> option,
4053                   an integer, is the maximum number of queries sent per
4054                   second.
4055                   The default is 20.
4056                 </p></dd>
4057 <dt><span class="term"><span><strong class="command">serial-queries</strong></span></span></dt>
4058 <dd><p>
4059                   In BIND 8, the <span><strong class="command">serial-queries</strong></span>
4060                   option
4061                   set the maximum number of concurrent serial number queries
4062                   allowed to be outstanding at any given time.
4063                   BIND 9 does not limit the number of outstanding
4064                   serial queries and ignores the <span><strong class="command">serial-queries</strong></span> option.
4065                   Instead, it limits the rate at which the queries are sent
4066                   as defined using the <span><strong class="command">serial-query-rate</strong></span> option.
4067                 </p></dd>
4068 <dt><span class="term"><span><strong class="command">transfer-format</strong></span></span></dt>
4069 <dd><p>
4070                   Zone transfers can be sent using two different formats,
4071                   <span><strong class="command">one-answer</strong></span> and
4072                   <span><strong class="command">many-answers</strong></span>.
4073                   The <span><strong class="command">transfer-format</strong></span> option is used
4074                   on the master server to determine which format it sends.
4075                   <span><strong class="command">one-answer</strong></span> uses one DNS message per
4076                   resource record transferred.
4077                   <span><strong class="command">many-answers</strong></span> packs as many resource
4078                   records as possible into a message.
4079                   <span><strong class="command">many-answers</strong></span> is more efficient, but is
4080                   only supported by relatively new slave servers,
4081                   such as <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
4082                   8.x and <acronym class="acronym">BIND</acronym> 4.9.5 onwards.
4083                   The <span><strong class="command">many-answers</strong></span> format is also supported by
4084                   recent Microsoft Windows nameservers.
4085                   The default is <span><strong class="command">many-answers</strong></span>.
4086                   <span><strong class="command">transfer-format</strong></span> may be overridden on a
4087                   per-server basis by using the <span><strong class="command">server</strong></span>
4088                   statement.
4089                 </p></dd>
4090 <dt><span class="term"><span><strong class="command">transfers-in</strong></span></span></dt>
4091 <dd><p>
4092                   The maximum number of inbound zone transfers
4093                   that can be running concurrently. The default value is <code class="literal">10</code>.
4094                   Increasing <span><strong class="command">transfers-in</strong></span> may
4095                   speed up the convergence
4096                   of slave zones, but it also may increase the load on the
4097                   local system.
4098                 </p></dd>
4099 <dt><span class="term"><span><strong class="command">transfers-out</strong></span></span></dt>
4100 <dd><p>
4101                   The maximum number of outbound zone transfers
4102                   that can be running concurrently. Zone transfer requests in
4103                   excess
4104                   of the limit will be refused. The default value is <code class="literal">10</code>.
4105                 </p></dd>
4106 <dt><span class="term"><span><strong class="command">transfers-per-ns</strong></span></span></dt>
4107 <dd><p>
4108                   The maximum number of inbound zone transfers
4109                   that can be concurrently transferring from a given remote
4110                   name server.
4111                   The default value is <code class="literal">2</code>.
4112                   Increasing <span><strong class="command">transfers-per-ns</strong></span>
4113                   may
4114                   speed up the convergence of slave zones, but it also may
4115                   increase
4116                   the load on the remote name server. <span><strong class="command">transfers-per-ns</strong></span> may
4117                   be overridden on a per-server basis by using the <span><strong class="command">transfers</strong></span> phrase
4118                   of the <span><strong class="command">server</strong></span> statement.
4119                 </p></dd>
4120 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
4121 <dd>
4122 <p><span><strong class="command">transfer-source</strong></span>
4123                   determines which local address will be bound to IPv4
4124                   TCP connections used to fetch zones transferred
4125                   inbound by the server.  It also determines the
4126                   source IPv4 address, and optionally the UDP port,
4127                   used for the refresh queries and forwarded dynamic
4128                   updates.  If not set, it defaults to a system
4129                   controlled value which will usually be the address
4130                   of the interface "closest to" the remote end. This
4131                   address must appear in the remote end's
4132                   <span><strong class="command">allow-transfer</strong></span> option for the
4133                   zone being transferred, if one is specified. This
4134                   statement sets the
4135                   <span><strong class="command">transfer-source</strong></span> for all zones,
4136                   but can be overridden on a per-view or per-zone
4137                   basis by including a
4138                   <span><strong class="command">transfer-source</strong></span> statement within
4139                   the <span><strong class="command">view</strong></span> or
4140                   <span><strong class="command">zone</strong></span> block in the configuration
4141                   file.
4142                 </p>
4143 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4144 <h3 class="title">Note</h3>
4145 <p>
4146                     Solaris 2.5.1 and earlier does not support setting the
4147                     source address for TCP sockets.
4148                   </p>
4149 </div>
4150 </dd>
4151 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
4152 <dd><p>
4153                   The same as <span><strong class="command">transfer-source</strong></span>,
4154                   except zone transfers are performed using IPv6.
4155                 </p></dd>
4156 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
4157 <dd>
4158 <p>
4159                   An alternate transfer source if the one listed in
4160                   <span><strong class="command">transfer-source</strong></span> fails and
4161                   <span><strong class="command">use-alt-transfer-source</strong></span> is
4162                   set.
4163                 </p>
4164 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4165 <h3 class="title">Note</h3>
4166                   If you do not wish the alternate transfer source
4167                   to be used, you should set
4168                   <span><strong class="command">use-alt-transfer-source</strong></span>
4169                   appropriately and you should not depend upon
4170                   getting an answer back to the first refresh
4171                   query.
4172                 </div>
4173 </dd>
4174 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
4175 <dd><p>
4176                   An alternate transfer source if the one listed in
4177                   <span><strong class="command">transfer-source-v6</strong></span> fails and
4178                   <span><strong class="command">use-alt-transfer-source</strong></span> is
4179                   set.
4180                 </p></dd>
4181 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
4182 <dd><p>
4183                   Use the alternate transfer sources or not.  If views are
4184                   specified this defaults to <span><strong class="command">no</strong></span>
4185                   otherwise it defaults to
4186                   <span><strong class="command">yes</strong></span> (for BIND 8
4187                   compatibility).
4188                 </p></dd>
4189 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
4190 <dd>
4191 <p><span><strong class="command">notify-source</strong></span>
4192                   determines which local source address, and
4193                   optionally UDP port, will be used to send NOTIFY
4194                   messages.  This address must appear in the slave
4195                   server's <span><strong class="command">masters</strong></span> zone clause or
4196                   in an <span><strong class="command">allow-notify</strong></span> clause.  This
4197                   statement sets the <span><strong class="command">notify-source</strong></span>
4198                   for all zones, but can be overridden on a per-zone or
4199                   per-view basis by including a
4200                   <span><strong class="command">notify-source</strong></span> statement within
4201                   the <span><strong class="command">zone</strong></span> or
4202                   <span><strong class="command">view</strong></span> block in the configuration
4203                   file.
4204                 </p>
4205 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4206 <h3 class="title">Note</h3>
4207 <p>
4208                     Solaris 2.5.1 and earlier does not support setting the
4209                     source address for TCP sockets.
4210                   </p>
4211 </div>
4212 </dd>
4213 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
4214 <dd><p>
4215                   Like <span><strong class="command">notify-source</strong></span>,
4216                   but applies to notify messages sent to IPv6 addresses.
4217                 </p></dd>
4218 </dl></div>
4219 </div>
4220 <div class="sect3" lang="en">
4221 <div class="titlepage"><div><div><h4 class="title">
4222 <a name="id2584644"></a>UDP Port Lists</h4></div></div></div>
4223 <p>
4224             <span><strong class="command">use-v4-udp-ports</strong></span>,
4225             <span><strong class="command">avoid-v4-udp-ports</strong></span>,
4226             <span><strong class="command">use-v6-udp-ports</strong></span>, and
4227             <span><strong class="command">avoid-v6-udp-ports</strong></span>
4228             specify a list of IPv4 and IPv6 UDP ports that will be
4229             used or not used as source ports for UDP messages.
4230             See <a href="Bv9ARM.ch06.html#query_address" title="Query Address">the section called &#8220;Query Address&#8221;</a> about how the
4231             available ports are determined.
4232             For example, with the following configuration
4233           </p>
4234 <pre class="programlisting">
4235 use-v6-udp-ports { range 32768 65535; };
4236 avoid-v6-udp-ports { 40000; range 50000 60000; };
4237 </pre>
4238 <p>
4239              UDP ports of IPv6 messages sent
4240              from <span><strong class="command">named</strong></span> will be in one
4241              of the following ranges: 32768 to 39999, 40001 to 49999,
4242              and 60001 to 65535.
4243            </p>
4244 <p>
4245              <span><strong class="command">avoid-v4-udp-ports</strong></span> and
4246              <span><strong class="command">avoid-v6-udp-ports</strong></span> can be used
4247              to prevent <span><strong class="command">named</strong></span> from choosing as its random source port a
4248              port that is blocked by your firewall or a port that is
4249              used by other applications;
4250              if a query went out with a source port blocked by a
4251              firewall, the
4252              answer would not get by the firewall and the name server would
4253              have to query again.
4254              Note: the desired range can also be represented only with
4255              <span><strong class="command">use-v4-udp-ports</strong></span> and
4256              <span><strong class="command">use-v6-udp-ports</strong></span>, and the
4257              <span><strong class="command">avoid-</strong></span> options are redundant in that
4258              sense; they are provided for backward compatibility and
4259              to possibly simplify the port specification.
4260            </p>
4261 </div>
4262 <div class="sect3" lang="en">
4263 <div class="titlepage"><div><div><h4 class="title">
4264 <a name="id2584704"></a>Operating System Resource Limits</h4></div></div></div>
4265 <p>
4266             The server's usage of many system resources can be limited.
4267             Scaled values are allowed when specifying resource limits.  For
4268             example, <span><strong class="command">1G</strong></span> can be used instead of
4269             <span><strong class="command">1073741824</strong></span> to specify a limit of
4270             one
4271             gigabyte. <span><strong class="command">unlimited</strong></span> requests
4272             unlimited use, or the
4273             maximum available amount. <span><strong class="command">default</strong></span>
4274             uses the limit
4275             that was in force when the server was started. See the description
4276             of <span><strong class="command">size_spec</strong></span> in <a href="Bv9ARM.ch06.html#configuration_file_elements" title="Configuration File Elements">the section called &#8220;Configuration File Elements&#8221;</a>.
4277           </p>
4278 <p>
4279             The following options set operating system resource limits for
4280             the name server process.  Some operating systems don't support
4281             some or
4282             any of the limits. On such systems, a warning will be issued if
4283             the
4284             unsupported limit is used.
4285           </p>
4286 <div class="variablelist"><dl>
4287 <dt><span class="term"><span><strong class="command">coresize</strong></span></span></dt>
4288 <dd><p>
4289                   The maximum size of a core dump. The default
4290                   is <code class="literal">default</code>.
4291                 </p></dd>
4292 <dt><span class="term"><span><strong class="command">datasize</strong></span></span></dt>
4293 <dd><p>
4294                   The maximum amount of data memory the server
4295                   may use. The default is <code class="literal">default</code>.
4296                   This is a hard limit on server memory usage.
4297                   If the server attempts to allocate memory in excess of this
4298                   limit, the allocation will fail, which may in turn leave
4299                   the server unable to perform DNS service.  Therefore,
4300                   this option is rarely useful as a way of limiting the
4301                   amount of memory used by the server, but it can be used
4302                   to raise an operating system data size limit that is
4303                   too small by default.  If you wish to limit the amount
4304                   of memory used by the server, use the
4305                   <span><strong class="command">max-cache-size</strong></span> and
4306                   <span><strong class="command">recursive-clients</strong></span>
4307                   options instead.
4308                 </p></dd>
4309 <dt><span class="term"><span><strong class="command">files</strong></span></span></dt>
4310 <dd><p>
4311                   The maximum number of files the server
4312                   may have open concurrently. The default is <code class="literal">unlimited</code>.
4313                 </p></dd>
4314 <dt><span class="term"><span><strong class="command">stacksize</strong></span></span></dt>
4315 <dd><p>
4316                   The maximum amount of stack memory the server
4317                   may use. The default is <code class="literal">default</code>.
4318                 </p></dd>
4319 </dl></div>
4320 </div>
4321 <div class="sect3" lang="en">
4322 <div class="titlepage"><div><div><h4 class="title">
4323 <a name="server_resource_limits"></a>Server  Resource Limits</h4></div></div></div>
4324 <p>
4325             The following options set limits on the server's
4326             resource consumption that are enforced internally by the
4327             server rather than the operating system.
4328           </p>
4329 <div class="variablelist"><dl>
4330 <dt><span class="term"><span><strong class="command">max-ixfr-log-size</strong></span></span></dt>
4331 <dd><p>
4332                   This option is obsolete; it is accepted
4333                   and ignored for BIND 8 compatibility.  The option
4334                   <span><strong class="command">max-journal-size</strong></span> performs a
4335                   similar function in BIND 9.
4336                 </p></dd>
4337 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
4338 <dd><p>
4339                   Sets a maximum size for each journal file
4340                   (see <a href="Bv9ARM.ch04.html#journal" title="The journal file">the section called &#8220;The journal file&#8221;</a>).  When the journal file
4341                   approaches
4342                   the specified size, some of the oldest transactions in the
4343                   journal
4344                   will be automatically removed.  The default is
4345                   <code class="literal">unlimited</code>.
4346                   This may also be set on a per-zone basis.
4347                 </p></dd>
4348 <dt><span class="term"><span><strong class="command">host-statistics-max</strong></span></span></dt>
4349 <dd><p>
4350                   In BIND 8, specifies the maximum number of host statistics
4351                   entries to be kept.
4352                   Not implemented in BIND 9.
4353                 </p></dd>
4354 <dt><span class="term"><span><strong class="command">recursive-clients</strong></span></span></dt>
4355 <dd><p>
4356                   The maximum number of simultaneous recursive lookups
4357                   the server will perform on behalf of clients.  The default
4358                   is
4359                   <code class="literal">1000</code>.  Because each recursing
4360                   client uses a fair
4361                   bit of memory, on the order of 20 kilobytes, the value of
4362                   the
4363                   <span><strong class="command">recursive-clients</strong></span> option may
4364                   have to be decreased
4365                   on hosts with limited memory.
4366                 </p></dd>
4367 <dt><span class="term"><span><strong class="command">tcp-clients</strong></span></span></dt>
4368 <dd><p>
4369                   The maximum number of simultaneous client TCP
4370                   connections that the server will accept.
4371                   The default is <code class="literal">100</code>.
4372                 </p></dd>
4373 <dt><span class="term"><span><strong class="command">reserved-sockets</strong></span></span></dt>
4374 <dd>
4375 <p>
4376                   The number of file descriptors reserved for TCP, stdio,
4377                   etc.  This needs to be big enough to cover the number of
4378                   interfaces <span><strong class="command">named</strong></span> listens on, <span><strong class="command">tcp-clients</strong></span> as well as
4379                   to provide room for outgoing TCP queries and incoming zone
4380                   transfers.  The default is <code class="literal">512</code>.
4381                   The minimum value is <code class="literal">128</code> and the
4382                   maximum value is <code class="literal">128</code> less than
4383                   maxsockets (-S).  This option may be removed in the future.
4384                 </p>
4385 <p>
4386                   This option has little effect on Windows.
4387                 </p>
4388 </dd>
4389 <dt><span class="term"><span><strong class="command">max-cache-size</strong></span></span></dt>
4390 <dd><p>
4391                   The maximum amount of memory to use for the
4392                   server's cache, in bytes.
4393                   When the amount of data in the cache
4394                   reaches this limit, the server will cause records to expire
4395                   prematurely based on an LRU based strategy so that
4396                   the limit is not exceeded.
4397                   A value of 0 is special, meaning that
4398                   records are purged from the cache only when their
4399                   TTLs expire.
4400                   Another special keyword <strong class="userinput"><code>unlimited</code></strong>
4401                   means the maximum value of 32-bit unsigned integers
4402                   (0xffffffff), which may not have the same effect as
4403                   0 on machines that support more than 32 bits of
4404                   memory space.
4405                   Any positive values less than 2MB will be ignored reset
4406                   to 2MB.
4407                   In a server with multiple views, the limit applies
4408                   separately to the cache of each view.
4409                   The default is 0.
4410                 </p></dd>
4411 <dt><span class="term"><span><strong class="command">tcp-listen-queue</strong></span></span></dt>
4412 <dd><p>
4413                   The listen queue depth.  The default and minimum is 3.
4414                   If the kernel supports the accept filter "dataready" this
4415                   also controls how
4416                   many TCP connections that will be queued in kernel space
4417                   waiting for
4418                   some data before being passed to accept.  Values less than 3
4419                   will be
4420                   silently raised.
4421                 </p></dd>
4422 </dl></div>
4423 </div>
4424 <div class="sect3" lang="en">
4425 <div class="titlepage"><div><div><h4 class="title">
4426 <a name="id2585194"></a>Periodic Task Intervals</h4></div></div></div>
4427 <div class="variablelist"><dl>
4428 <dt><span class="term"><span><strong class="command">cleaning-interval</strong></span></span></dt>
4429 <dd><p>
4430                   This interval is effectively obsolete.  Previously,
4431                   the server would remove expired resource records
4432                   from the cache every <span><strong class="command">cleaning-interval</strong></span> minutes.
4433                   <acronym class="acronym">BIND</acronym> 9 now manages cache
4434                   memory in a more sophisticated manner and does not
4435                   rely on the periodic cleaning any more.
4436                   Specifying this option therefore has no effect on
4437                   the server's behavior.
4438                 </p></dd>
4439 <dt><span class="term"><span><strong class="command">heartbeat-interval</strong></span></span></dt>
4440 <dd><p>
4441                   The server will perform zone maintenance tasks
4442                   for all zones marked as <span><strong class="command">dialup</strong></span> whenever this
4443                   interval expires. The default is 60 minutes. Reasonable
4444                   values are up
4445                   to 1 day (1440 minutes).  The maximum value is 28 days
4446                   (40320 minutes).
4447                   If set to 0, no zone maintenance for these zones will occur.
4448                 </p></dd>
4449 <dt><span class="term"><span><strong class="command">interface-interval</strong></span></span></dt>
4450 <dd><p>
4451                   The server will scan the network interface list
4452                   every <span><strong class="command">interface-interval</strong></span>
4453                   minutes. The default
4454                   is 60 minutes. The maximum value is 28 days (40320 minutes).
4455                   If set to 0, interface scanning will only occur when
4456                   the configuration file is  loaded. After the scan, the
4457                   server will
4458                   begin listening for queries on any newly discovered
4459                   interfaces (provided they are allowed by the
4460                   <span><strong class="command">listen-on</strong></span> configuration), and
4461                   will
4462                   stop listening on interfaces that have gone away.
4463                 </p></dd>
4464 <dt><span class="term"><span><strong class="command">statistics-interval</strong></span></span></dt>
4465 <dd>
4466 <p>
4467                   Name server statistics will be logged
4468                   every <span><strong class="command">statistics-interval</strong></span>
4469                   minutes. The default is
4470                   60. The maximum value is 28 days (40320 minutes).
4471                   If set to 0, no statistics will be logged.
4472                   </p>
4473 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4474 <h3 class="title">Note</h3>
4475 <p>
4476                     Not yet implemented in
4477                     <acronym class="acronym">BIND</acronym> 9.
4478                   </p>
4479 </div>
4480 </dd>
4481 </dl></div>
4482 </div>
4483 <div class="sect3" lang="en">
4484 <div class="titlepage"><div><div><h4 class="title">
4485 <a name="topology"></a>Topology</h4></div></div></div>
4486 <p>
4487             All other things being equal, when the server chooses a name
4488             server
4489             to query from a list of name servers, it prefers the one that is
4490             topologically closest to itself. The <span><strong class="command">topology</strong></span> statement
4491             takes an <span><strong class="command">address_match_list</strong></span> and
4492             interprets it
4493             in a special way. Each top-level list element is assigned a
4494             distance.
4495             Non-negated elements get a distance based on their position in the
4496             list, where the closer the match is to the start of the list, the
4497             shorter the distance is between it and the server. A negated match
4498             will be assigned the maximum distance from the server. If there
4499             is no match, the address will get a distance which is further than
4500             any non-negated list element, and closer than any negated element.
4501             For example,
4502           </p>
4503 <pre class="programlisting">topology {
4504     10/8;
4505     !1.2.3/24;
4506     { 1.2/16; 3/8; };
4507 };</pre>
4508 <p>
4509             will prefer servers on network 10 the most, followed by hosts
4510             on network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the
4511             exception of hosts on network 1.2.3 (netmask 255.255.255.0), which
4512             is preferred least of all.
4513           </p>
4514 <p>
4515             The default topology is
4516           </p>
4517 <pre class="programlisting">    topology { localhost; localnets; };
4518 </pre>
4519 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4520 <h3 class="title">Note</h3>
4521 <p>
4522               The <span><strong class="command">topology</strong></span> option
4523               is not implemented in <acronym class="acronym">BIND</acronym> 9.
4524             </p>
4525 </div>
4526 </div>
4527 <div class="sect3" lang="en">
4528 <div class="titlepage"><div><div><h4 class="title">
4529 <a name="the_sortlist_statement"></a>The <span><strong class="command">sortlist</strong></span> Statement</h4></div></div></div>
4530 <p>
4531             The response to a DNS query may consist of multiple resource
4532             records (RRs) forming a resource records set (RRset).
4533             The name server will normally return the
4534             RRs within the RRset in an indeterminate order
4535             (but see the <span><strong class="command">rrset-order</strong></span>
4536             statement in <a href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">the section called &#8220;RRset Ordering&#8221;</a>).
4537             The client resolver code should rearrange the RRs as appropriate,
4538             that is, using any addresses on the local net in preference to
4539             other addresses.
4540             However, not all resolvers can do this or are correctly
4541             configured.
4542             When a client is using a local server, the sorting can be performed
4543             in the server, based on the client's address. This only requires
4544             configuring the name servers, not all the clients.
4545           </p>
4546 <p>
4547             The <span><strong class="command">sortlist</strong></span> statement (see below)
4548             takes
4549             an <span><strong class="command">address_match_list</strong></span> and
4550             interprets it even
4551             more specifically than the <span><strong class="command">topology</strong></span>
4552             statement
4553             does (<a href="Bv9ARM.ch06.html#topology" title="Topology">the section called &#8220;Topology&#8221;</a>).
4554             Each top level statement in the <span><strong class="command">sortlist</strong></span> must
4555             itself be an explicit <span><strong class="command">address_match_list</strong></span> with
4556             one or two elements. The first element (which may be an IP
4557             address,
4558             an IP prefix, an ACL name or a nested <span><strong class="command">address_match_list</strong></span>)
4559             of each top level list is checked against the source address of
4560             the query until a match is found.
4561           </p>
4562 <p>
4563             Once the source address of the query has been matched, if
4564             the top level statement contains only one element, the actual
4565             primitive
4566             element that matched the source address is used to select the
4567             address
4568             in the response to move to the beginning of the response. If the
4569             statement is a list of two elements, then the second element is
4570             treated the same as the <span><strong class="command">address_match_list</strong></span> in
4571             a <span><strong class="command">topology</strong></span> statement. Each top
4572             level element
4573             is assigned a distance and the address in the response with the
4574             minimum
4575             distance is moved to the beginning of the response.
4576           </p>
4577 <p>
4578             In the following example, any queries received from any of
4579             the addresses of the host itself will get responses preferring
4580             addresses
4581             on any of the locally connected networks. Next most preferred are
4582             addresses
4583             on the 192.168.1/24 network, and after that either the
4584             192.168.2/24
4585             or
4586             192.168.3/24 network with no preference shown between these two
4587             networks. Queries received from a host on the 192.168.1/24 network
4588             will prefer other addresses on that network to the 192.168.2/24
4589             and
4590             192.168.3/24 networks. Queries received from a host on the
4591             192.168.4/24
4592             or the 192.168.5/24 network will only prefer other addresses on
4593             their directly connected networks.
4594           </p>
4595 <pre class="programlisting">sortlist {
4596     // IF the local host
4597     // THEN first fit on the following nets
4598     { localhost;
4599         { localnets;
4600             192.168.1/24;
4601             { 192.168.2/24; 192.168.3/24; }; }; };
4602     // IF on class C 192.168.1 THEN use .1, or .2 or .3
4603     { 192.168.1/24;
4604         { 192.168.1/24;
4605             { 192.168.2/24; 192.168.3/24; }; }; };
4606     // IF on class C 192.168.2 THEN use .2, or .1 or .3
4607     { 192.168.2/24;
4608         { 192.168.2/24;
4609             { 192.168.1/24; 192.168.3/24; }; }; };
4610     // IF on class C 192.168.3 THEN use .3, or .1 or .2
4611     { 192.168.3/24;
4612         { 192.168.3/24;
4613             { 192.168.1/24; 192.168.2/24; }; }; };
4614     // IF .4 or .5 THEN prefer that net
4615     { { 192.168.4/24; 192.168.5/24; };
4616     };
4617 };</pre>
4618 <p>
4619             The following example will give reasonable behavior for the
4620             local host and hosts on directly connected networks. It is similar
4621             to the behavior of the address sort in <acronym class="acronym">BIND</acronym> 4.9.x. Responses sent
4622             to queries from the local host will favor any of the directly
4623             connected
4624             networks. Responses sent to queries from any other hosts on a
4625             directly
4626             connected network will prefer addresses on that same network.
4627             Responses
4628             to other queries will not be sorted.
4629           </p>
4630 <pre class="programlisting">sortlist {
4631            { localhost; localnets; };
4632            { localnets; };
4633 };
4634 </pre>
4635 </div>
4636 <div class="sect3" lang="en">
4637 <div class="titlepage"><div><div><h4 class="title">
4638 <a name="rrset_ordering"></a>RRset Ordering</h4></div></div></div>
4639 <p>
4640             When multiple records are returned in an answer it may be
4641             useful to configure the order of the records placed into the
4642             response.
4643             The <span><strong class="command">rrset-order</strong></span> statement permits
4644             configuration
4645             of the ordering of the records in a multiple record response.
4646             See also the <span><strong class="command">sortlist</strong></span> statement,
4647             <a href="Bv9ARM.ch06.html#the_sortlist_statement" title="The sortlist Statement">the section called &#8220;The <span><strong class="command">sortlist</strong></span> Statement&#8221;</a>.
4648           </p>
4649 <p>
4650             An <span><strong class="command">order_spec</strong></span> is defined as
4651             follows:
4652           </p>
4653 <p>
4654             [<span class="optional">class <em class="replaceable"><code>class_name</code></em></span>]
4655             [<span class="optional">type <em class="replaceable"><code>type_name</code></em></span>]
4656             [<span class="optional">name <em class="replaceable"><code>"domain_name"</code></em></span>]
4657             order <em class="replaceable"><code>ordering</code></em>
4658           </p>
4659 <p>
4660             If no class is specified, the default is <span><strong class="command">ANY</strong></span>.
4661             If no type is specified, the default is <span><strong class="command">ANY</strong></span>.
4662             If no name is specified, the default is "<span><strong class="command">*</strong></span>" (asterisk).
4663           </p>
4664 <p>
4665             The legal values for <span><strong class="command">ordering</strong></span> are:
4666           </p>
4667 <div class="informaltable"><table border="1">
4668 <colgroup>
4669 <col>
4670 <col>
4671 </colgroup>
4672 <tbody>
4673 <tr>
4674 <td>
4675                     <p><span><strong class="command">fixed</strong></span></p>
4676                   </td>
4677 <td>
4678                     <p>
4679                       Records are returned in the order they
4680                       are defined in the zone file.
4681                     </p>
4682                   </td>
4683 </tr>
4684 <tr>
4685 <td>
4686                     <p><span><strong class="command">random</strong></span></p>
4687                   </td>
4688 <td>
4689                     <p>
4690                       Records are returned in some random order.
4691                     </p>
4692                   </td>
4693 </tr>
4694 <tr>
4695 <td>
4696                     <p><span><strong class="command">cyclic</strong></span></p>
4697                   </td>
4698 <td>
4699                     <p>
4700                       Records are returned in a cyclic round-robin order.
4701                     </p>
4702                     <p>
4703                       If <acronym class="acronym">BIND</acronym> is configured with the
4704                       "--enable-fixed-rrset" option at compile time, then
4705                       the initial ordering of the RRset will match the
4706                       one specified in the zone file.
4707                     </p>
4708                   </td>
4709 </tr>
4710 </tbody>
4711 </table></div>
4712 <p>
4713             For example:
4714           </p>
4715 <pre class="programlisting">rrset-order {
4716    class IN type A name "host.example.com" order random;
4717    order cyclic;
4718 };
4719 </pre>
4720 <p>
4721             will cause any responses for type A records in class IN that
4722             have "<code class="literal">host.example.com</code>" as a
4723             suffix, to always be returned
4724             in random order. All other records are returned in cyclic order.
4725           </p>
4726 <p>
4727             If multiple <span><strong class="command">rrset-order</strong></span> statements
4728             appear,
4729             they are not combined &#8212; the last one applies.
4730           </p>
4731 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4732 <h3 class="title">Note</h3>
4733 <p>
4734               In this release of <acronym class="acronym">BIND</acronym> 9, the
4735               <span><strong class="command">rrset-order</strong></span> statement does not support
4736               "fixed" ordering by default.  Fixed ordering can be enabled
4737               at compile time by specifying "--enable-fixed-rrset" on
4738               the "configure" command line.
4739             </p>
4740 </div>
4741 </div>
4742 <div class="sect3" lang="en">
4743 <div class="titlepage"><div><div><h4 class="title">
4744 <a name="tuning"></a>Tuning</h4></div></div></div>
4745 <div class="variablelist"><dl>
4746 <dt><span class="term"><span><strong class="command">lame-ttl</strong></span></span></dt>
4747 <dd>
4748 <p>
4749                   Sets the number of seconds to cache a
4750                   lame server indication. 0 disables caching. (This is
4751                   <span class="bold"><strong>NOT</strong></span> recommended.)
4752                   The default is <code class="literal">600</code> (10 minutes) and the
4753                   maximum value is
4754                   <code class="literal">1800</code> (30 minutes).
4755                 </p>
4756 <p>
4757                   Lame-ttl also controls the amount of time DNSSEC
4758                   validation failures are cached.  There is a minimum
4759                   of 30 seconds applied to bad cache entries if the
4760                   lame-ttl is set to less than 30 seconds.
4761                 </p>
4762 </dd>
4763 <dt><span class="term"><span><strong class="command">max-ncache-ttl</strong></span></span></dt>
4764 <dd><p>
4765                   To reduce network traffic and increase performance,
4766                   the server stores negative answers. <span><strong class="command">max-ncache-ttl</strong></span> is
4767                   used to set a maximum retention time for these answers in
4768                   the server
4769                   in seconds. The default
4770                   <span><strong class="command">max-ncache-ttl</strong></span> is <code class="literal">10800</code> seconds (3 hours).
4771                   <span><strong class="command">max-ncache-ttl</strong></span> cannot exceed
4772                   7 days and will
4773                   be silently truncated to 7 days if set to a greater value.
4774                 </p></dd>
4775 <dt><span class="term"><span><strong class="command">max-cache-ttl</strong></span></span></dt>
4776 <dd><p>
4777                   Sets the maximum time for which the server will
4778                   cache ordinary (positive) answers. The default is
4779                   one week (7 days).
4780                   A value of zero may cause all queries to return
4781                   SERVFAIL, because of lost caches of intermediate
4782                   RRsets (such as NS and glue AAAA/A records) in the
4783                   resolution process.
4784                 </p></dd>
4785 <dt><span class="term"><span><strong class="command">min-roots</strong></span></span></dt>
4786 <dd>
4787 <p>
4788                   The minimum number of root servers that
4789                   is required for a request for the root servers to be
4790                   accepted. The default
4791                   is <strong class="userinput"><code>2</code></strong>.
4792                 </p>
4793 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4794 <h3 class="title">Note</h3>
4795 <p>
4796                     Not implemented in <acronym class="acronym">BIND</acronym> 9.
4797                   </p>
4798 </div>
4799 </dd>
4800 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
4801 <dd>
4802 <p>
4803                   Specifies the number of days into the future when
4804                   DNSSEC signatures automatically generated as a
4805                   result of dynamic updates (<a href="Bv9ARM.ch04.html#dynamic_update" title="Dynamic Update">the section called &#8220;Dynamic Update&#8221;</a>) will expire.  There
4806                   is an optional second field which specifies how
4807                   long before expiry that the signatures will be
4808                   regenerated.  If not specified, the signatures will
4809                   be regenerated at 1/4 of base interval.  The second
4810                   field is specified in days if the base interval is
4811                   greater than 7 days otherwise it is specified in hours.
4812                   The default base interval is <code class="literal">30</code> days
4813                   giving a re-signing interval of 7 1/2 days.  The maximum
4814                   values are 10 years (3660 days).
4815                 </p>
4816 <p>
4817                   The signature inception time is unconditionally
4818                   set to one hour before the current time to allow
4819                   for a limited amount of clock skew.
4820                 </p>
4821 <p>
4822                   The <span><strong class="command">sig-validity-interval</strong></span>
4823                   should be, at least, several multiples of the SOA
4824                   expire interval to allow for reasonable interaction
4825                   between the various timer and expiry dates.
4826                 </p>
4827 </dd>
4828 <dt><span class="term"><span><strong class="command">sig-signing-nodes</strong></span></span></dt>
4829 <dd><p>
4830                   Specify the maximum number of nodes to be
4831                   examined in each quantum when signing a zone with
4832                   a new DNSKEY. The default is
4833                   <code class="literal">100</code>.
4834                 </p></dd>
4835 <dt><span class="term"><span><strong class="command">sig-signing-signatures</strong></span></span></dt>
4836 <dd><p>
4837                   Specify a threshold number of signatures that
4838                   will terminate processing a quantum when signing
4839                   a zone with a new DNSKEY.  The default is
4840                   <code class="literal">10</code>.
4841                 </p></dd>
4842 <dt><span class="term"><span><strong class="command">sig-signing-type</strong></span></span></dt>
4843 <dd>
4844 <p>
4845                   Specify a private RDATA type to be used when generating
4846                   key signing records.  The default is
4847                   <code class="literal">65535</code>.
4848                 </p>
4849 <p>
4850                   It is expected that this parameter may be removed
4851                   in a future version once there is a standard type.
4852                 </p>
4853 </dd>
4854 <dt>
4855 <span class="term"><span><strong class="command">min-refresh-time</strong></span>, </span><span class="term"><span><strong class="command">max-refresh-time</strong></span>, </span><span class="term"><span><strong class="command">min-retry-time</strong></span>, </span><span class="term"><span><strong class="command">max-retry-time</strong></span></span>
4856 </dt>
4857 <dd>
4858 <p>
4859                   These options control the server's behavior on refreshing a
4860                   zone
4861                   (querying for SOA changes) or retrying failed transfers.
4862                   Usually the SOA values for the zone are used, but these
4863                   values
4864                   are set by the master, giving slave server administrators
4865                   little
4866                   control over their contents.
4867                 </p>
4868 <p>
4869                   These options allow the administrator to set a minimum and
4870                   maximum
4871                   refresh and retry time either per-zone, per-view, or
4872                   globally.
4873                   These options are valid for slave and stub zones,
4874                   and clamp the SOA refresh and retry times to the specified
4875                   values.
4876                 </p>
4877 </dd>
4878 <dt><span class="term"><span><strong class="command">edns-udp-size</strong></span></span></dt>
4879 <dd>
4880 <p>
4881                   Sets the advertised EDNS UDP buffer size in bytes
4882                   to control the size of packets received.
4883                   Valid values are 1024 to 4096 (values outside this range
4884                   will be silently adjusted).  The default value
4885                   is 4096.  The usual reason for setting
4886                   <span><strong class="command">edns-udp-size</strong></span> to a non-default
4887                   value is to get UDP answers to pass through broken
4888                   firewalls that block fragmented packets and/or
4889                   block UDP packets that are greater than 512 bytes.
4890                 </p>
4891 <p>
4892                   <span><strong class="command">named</strong></span> will fallback to using 512 bytes
4893                   if it get a series of timeout at the initial value.  512
4894                   bytes is not being offered to encourage sites to fix their
4895                   firewalls.  Small EDNS UDP sizes will result in the
4896                   excessive use of TCP.
4897                 </p>
4898 </dd>
4899 <dt><span class="term"><span><strong class="command">max-udp-size</strong></span></span></dt>
4900 <dd>
4901 <p>
4902                   Sets the maximum EDNS UDP message size
4903                   <span><strong class="command">named</strong></span> will send in bytes.
4904                   Valid values are 512 to 4096 (values outside this
4905                   range will be silently adjusted).  The default
4906                   value is 4096.  The usual reason for setting
4907                   <span><strong class="command">max-udp-size</strong></span> to a non-default
4908                   value is to get UDP answers to pass through broken
4909                   firewalls that block fragmented packets and/or
4910                   block UDP packets that are greater than 512 bytes.
4911                   This is independent of the advertised receive
4912                   buffer (<span><strong class="command">edns-udp-size</strong></span>).
4913                 </p>
4914 <p>
4915                   Setting this to a low value will encourge additional
4916                   TCP traffic to the nameserver.
4917                 </p>
4918 </dd>
4919 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
4920 <dd><p>Specifies
4921                   the file format of zone files (see
4922                   <a href="Bv9ARM.ch06.html#zonefile_format" title="Additional File Formats">the section called &#8220;Additional File Formats&#8221;</a>).
4923                   The default value is <code class="constant">text</code>, which is the
4924                   standard textual representation.  Files in other formats
4925                   than <code class="constant">text</code> are typically expected
4926                   to be generated by the <span><strong class="command">named-compilezone</strong></span> tool.
4927                   Note that when a zone file in a different format than
4928                   <code class="constant">text</code> is loaded, <span><strong class="command">named</strong></span>
4929                   may omit some of the checks which would be performed for a
4930                   file in the <code class="constant">text</code> format.  In particular,
4931                   <span><strong class="command">check-names</strong></span> checks do not apply
4932                   for the <code class="constant">raw</code> format.  This means
4933                   a zone file in the <code class="constant">raw</code> format
4934                   must be generated with the same check level as that
4935                   specified in the <span><strong class="command">named</strong></span> configuration
4936                   file.  This statement sets the
4937                   <span><strong class="command">masterfile-format</strong></span> for all zones,
4938                   but can be overridden on a per-zone or per-view basis
4939                   by including a <span><strong class="command">masterfile-format</strong></span>
4940                   statement within the <span><strong class="command">zone</strong></span> or
4941                   <span><strong class="command">view</strong></span> block in the configuration
4942                   file.
4943                 </p></dd>
4944 <dt>
4945 <a name="clients-per-query"></a><span class="term"><span><strong class="command">clients-per-query</strong></span>, </span><span class="term"><span><strong class="command">max-clients-per-query</strong></span></span>
4946 </dt>
4947 <dd>
4948 <p>These set the
4949                   initial value (minimum) and maximum number of recursive
4950                   simultaneous clients for any given query
4951                   (&lt;qname,qtype,qclass&gt;) that the server will accept
4952                   before dropping additional clients.  <span><strong class="command">named</strong></span> will attempt to
4953                   self tune this value and changes will be logged.  The
4954                   default values are 10 and 100.
4955                 </p>
4956 <p>
4957                   This value should reflect how many queries come in for
4958                   a given name in the time it takes to resolve that name.
4959                   If the number of queries exceed this value, <span><strong class="command">named</strong></span> will
4960                   assume that it is dealing with a non-responsive zone
4961                   and will drop additional queries.  If it gets a response
4962                   after dropping queries, it will raise the estimate.  The
4963                   estimate will then be lowered in 20 minutes if it has
4964                   remained unchanged.
4965                 </p>
4966 <p>
4967                   If <span><strong class="command">clients-per-query</strong></span> is set to zero,
4968                   then there is no limit on the number of clients per query
4969                   and no queries will be dropped.
4970                 </p>
4971 <p>
4972                   If <span><strong class="command">max-clients-per-query</strong></span> is set to zero,
4973                   then there is no upper bound other than imposed by
4974                   <span><strong class="command">recursive-clients</strong></span>.
4975                 </p>
4976 </dd>
4977 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
4978 <dd><p>
4979                   The delay, in seconds, between sending sets of notify
4980                   messages for a zone.  The default is five (5) seconds.
4981                 </p></dd>
4982 </dl></div>
4983 </div>
4984 <div class="sect3" lang="en">
4985 <div class="titlepage"><div><div><h4 class="title">
4986 <a name="builtin"></a>Built-in server information zones</h4></div></div></div>
4987 <p>
4988             The server provides some helpful diagnostic information
4989             through a number of built-in zones under the
4990             pseudo-top-level-domain <code class="literal">bind</code> in the
4991             <span><strong class="command">CHAOS</strong></span> class.  These zones are part
4992             of a
4993             built-in view (see <a href="Bv9ARM.ch06.html#view_statement_grammar" title="view Statement Grammar">the section called &#8220;<span><strong class="command">view</strong></span> Statement Grammar&#8221;</a>) of
4994             class
4995             <span><strong class="command">CHAOS</strong></span> which is separate from the
4996             default view of
4997             class <span><strong class="command">IN</strong></span>; therefore, any global
4998             server options
4999             such as <span><strong class="command">allow-query</strong></span> do not apply
5000             the these zones.
5001             If you feel the need to disable these zones, use the options
5002             below, or hide the built-in <span><strong class="command">CHAOS</strong></span>
5003             view by
5004             defining an explicit view of class <span><strong class="command">CHAOS</strong></span>
5005             that matches all clients.
5006           </p>
5007 <div class="variablelist"><dl>
5008 <dt><span class="term"><span><strong class="command">version</strong></span></span></dt>
5009 <dd><p>
5010                   The version the server should report
5011                   via a query of the name <code class="literal">version.bind</code>
5012                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5013                   The default is the real version number of this server.
5014                   Specifying <span><strong class="command">version none</strong></span>
5015                   disables processing of the queries.
5016                 </p></dd>
5017 <dt><span class="term"><span><strong class="command">hostname</strong></span></span></dt>
5018 <dd><p>
5019                   The hostname the server should report via a query of
5020                   the name <code class="filename">hostname.bind</code>
5021                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5022                   This defaults to the hostname of the machine hosting the
5023                   name server as
5024                   found by the gethostname() function.  The primary purpose of such queries
5025                   is to
5026                   identify which of a group of anycast servers is actually
5027                   answering your queries.  Specifying <span><strong class="command">hostname none;</strong></span>
5028                   disables processing of the queries.
5029                 </p></dd>
5030 <dt><span class="term"><span><strong class="command">server-id</strong></span></span></dt>
5031 <dd><p>
5032                   The ID the server should report when receiving a Name
5033                   Server Identifier (NSID) query, or a query of the name
5034                   <code class="filename">ID.SERVER</code> with type
5035                   <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5036                   The primary purpose of such queries is to
5037                   identify which of a group of anycast servers is actually
5038                   answering your queries.  Specifying <span><strong class="command">server-id none;</strong></span>
5039                   disables processing of the queries.
5040                   Specifying <span><strong class="command">server-id hostname;</strong></span> will cause <span><strong class="command">named</strong></span> to
5041                   use the hostname as found by the gethostname() function.
5042                   The default <span><strong class="command">server-id</strong></span> is <span><strong class="command">none</strong></span>.
5043                 </p></dd>
5044 </dl></div>
5045 </div>
5046 <div class="sect3" lang="en">
5047 <div class="titlepage"><div><div><h4 class="title">
5048 <a name="empty"></a>Built-in Empty Zones</h4></div></div></div>
5049 <p>
5050             Named has some built-in empty zones (SOA and NS records only).
5051             These are for zones that should normally be answered locally
5052             and which queries should not be sent to the Internet's root
5053             servers.  The official servers which cover these namespaces
5054             return NXDOMAIN responses to these queries.  In particular,
5055             these cover the reverse namespace for addresses from RFC 1918 and
5056             RFC 3330.  They also include the reverse namespace for IPv6 local
5057             address (locally assigned), IPv6 link local addresses, the IPv6
5058             loopback address and the IPv6 unknown address.
5059           </p>
5060 <p>
5061             Named will attempt to determine if a built-in zone already exists
5062             or is active (covered by a forward-only forwarding declaration)
5063             and will not create an empty zone in that case.
5064           </p>
5065 <p>
5066             The current list of empty zones is:
5067             </p>
5068 <div class="itemizedlist"><ul type="disc">
5069 <li>0.IN-ADDR.ARPA</li>
5070 <li>127.IN-ADDR.ARPA</li>
5071 <li>254.169.IN-ADDR.ARPA</li>
5072 <li>2.0.192.IN-ADDR.ARPA</li>
5073 <li>255.255.255.255.IN-ADDR.ARPA</li>
5074 <li>0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA</li>
5075 <li>1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA</li>
5076 <li>D.F.IP6.ARPA</li>
5077 <li>8.E.F.IP6.ARPA</li>
5078 <li>9.E.F.IP6.ARPA</li>
5079 <li>A.E.F.IP6.ARPA</li>
5080 <li>B.E.F.IP6.ARPA</li>
5081 </ul></div>
5082 <p>
5083           </p>
5084 <p>
5085             Empty zones are settable at the view level and only apply to
5086             views of class IN.  Disabled empty zones are only inherited
5087             from options if there are no disabled empty zones specified
5088             at the view level.  To override the options list of disabled
5089             zones, you can disable the root zone at the view level, for example:
5090 </p>
5091 <pre class="programlisting">
5092             disable-empty-zone ".";
5093 </pre>
5094 <p>
5095           </p>
5096 <p>
5097             If you are using the address ranges covered here, you should
5098             already have reverse zones covering the addresses you use.
5099             In practice this appears to not be the case with many queries
5100             being made to the infrastructure servers for names in these
5101             spaces.  So many in fact that sacrificial servers were needed
5102             to be deployed to channel the query load away from the
5103             infrastructure servers.
5104           </p>
5105 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5106 <h3 class="title">Note</h3>
5107             The real parent servers for these zones should disable all
5108             empty zone under the parent zone they serve.  For the real
5109             root servers, this is all built-in empty zones.  This will
5110             enable them to return referrals to deeper in the tree.
5111           </div>
5112 <div class="variablelist"><dl>
5113 <dt><span class="term"><span><strong class="command">empty-server</strong></span></span></dt>
5114 <dd><p>
5115                   Specify what server name will appear in the returned
5116                   SOA record for empty zones.  If none is specified, then
5117                   the zone's name will be used.
5118                 </p></dd>
5119 <dt><span class="term"><span><strong class="command">empty-contact</strong></span></span></dt>
5120 <dd><p>
5121                   Specify what contact name will appear in the returned
5122                   SOA record for empty zones.  If none is specified, then
5123                   "." will be used.
5124                 </p></dd>
5125 <dt><span class="term"><span><strong class="command">empty-zones-enable</strong></span></span></dt>
5126 <dd><p>
5127                   Enable or disable all empty zones.  By default, they
5128                   are enabled.
5129                 </p></dd>
5130 <dt><span class="term"><span><strong class="command">disable-empty-zone</strong></span></span></dt>
5131 <dd><p>
5132                   Disable individual empty zones.  By default, none are
5133                   disabled.  This option can be specified multiple times.
5134                 </p></dd>
5135 </dl></div>
5136 </div>
5137 <div class="sect3" lang="en">
5138 <div class="titlepage"><div><div><h4 class="title">
5139 <a name="acache"></a>Additional Section Caching</h4></div></div></div>
5140 <p>
5141             The additional section cache, also called <span><strong class="command">acache</strong></span>,
5142             is an internal cache to improve the response performance of BIND 9.
5143             When additional section caching is enabled, BIND 9 will
5144             cache an internal short-cut to the additional section content for
5145             each answer RR.
5146             Note that <span><strong class="command">acache</strong></span> is an internal caching
5147             mechanism of BIND 9, and is not related to the DNS caching
5148             server function.
5149           </p>
5150 <p>
5151             Additional section caching does not change the
5152             response content (except the RRsets ordering of the additional
5153             section, see below), but can improve the response performance
5154             significantly.
5155             It is particularly effective when BIND 9 acts as an authoritative
5156             server for a zone that has many delegations with many glue RRs.
5157           </p>
5158 <p>
5159             In order to obtain the maximum performance improvement
5160             from additional section caching, setting
5161             <span><strong class="command">additional-from-cache</strong></span>
5162             to <span><strong class="command">no</strong></span> is recommended, since the current
5163             implementation of <span><strong class="command">acache</strong></span>
5164             does not short-cut of additional section information from the
5165             DNS cache data.
5166           </p>
5167 <p>
5168             One obvious disadvantage of <span><strong class="command">acache</strong></span> is
5169             that it requires much more
5170             memory for the internal cached data.
5171             Thus, if the response performance does not matter and memory
5172             consumption is much more critical, the
5173             <span><strong class="command">acache</strong></span> mechanism can be
5174             disabled by setting <span><strong class="command">acache-enable</strong></span> to
5175             <span><strong class="command">no</strong></span>.
5176             It is also possible to specify the upper limit of memory
5177             consumption
5178             for acache by using <span><strong class="command">max-acache-size</strong></span>.
5179           </p>
5180 <p>
5181             Additional section caching also has a minor effect on the
5182             RRset ordering in the additional section.
5183             Without <span><strong class="command">acache</strong></span>,
5184             <span><strong class="command">cyclic</strong></span> order is effective for the additional
5185             section as well as the answer and authority sections.
5186             However, additional section caching fixes the ordering when it
5187             first caches an RRset for the additional section, and the same
5188             ordering will be kept in succeeding responses, regardless of the
5189             setting of <span><strong class="command">rrset-order</strong></span>.
5190             The effect of this should be minor, however, since an
5191             RRset in the additional section
5192             typically only contains a small number of RRs (and in many cases
5193             it only contains a single RR), in which case the
5194             ordering does not matter much.
5195           </p>
5196 <p>
5197             The following is a summary of options related to
5198             <span><strong class="command">acache</strong></span>.
5199           </p>
5200 <div class="variablelist"><dl>
5201 <dt><span class="term"><span><strong class="command">acache-enable</strong></span></span></dt>
5202 <dd><p>
5203                   If <span><strong class="command">yes</strong></span>, additional section caching is
5204                   enabled.  The default value is <span><strong class="command">no</strong></span>.
5205                 </p></dd>
5206 <dt><span class="term"><span><strong class="command">acache-cleaning-interval</strong></span></span></dt>
5207 <dd><p>
5208                   The server will remove stale cache entries, based on an LRU
5209                   based
5210                   algorithm, every <span><strong class="command">acache-cleaning-interval</strong></span> minutes.
5211                   The default is 60 minutes.
5212                   If set to 0, no periodic cleaning will occur.
5213                 </p></dd>
5214 <dt><span class="term"><span><strong class="command">max-acache-size</strong></span></span></dt>
5215 <dd><p>
5216                   The maximum amount of memory in bytes to use for the server's acache.
5217                   When the amount of data in the acache reaches this limit,
5218                   the server
5219                   will clean more aggressively so that the limit is not
5220                   exceeded.
5221                   In a server with multiple views, the limit applies
5222                   separately to the
5223                   acache of each view.
5224                   The default is <code class="literal">16M</code>.
5225                 </p></dd>
5226 </dl></div>
5227 </div>
5228 <div class="sect3" lang="en">
5229 <div class="titlepage"><div><div><h4 class="title">
5230 <a name="id2587277"></a>Content Filtering</h4></div></div></div>
5231 <p>
5232             <acronym class="acronym">BIND</acronym> 9 provides the ability to filter
5233             out DNS responses from external DNS servers containing
5234             certain types of data in the answer section.
5235             Specifically, it can reject address (A or AAAA) records if
5236             the corresponding IPv4 or IPv6 addresses match the given
5237             <code class="varname">address_match_list</code> of the
5238             <span><strong class="command">deny-answer-addresses</strong></span> option.
5239             It can also reject CNAME or DNAME records if the "alias"
5240             name (i.e., the CNAME alias or the substituted query name
5241             due to DNAME) matches the
5242             given <code class="varname">namelist</code> of the
5243             <span><strong class="command">deny-answer-aliases</strong></span> option, where
5244             "match" means the alias name is a subdomain of one of
5245             the <code class="varname">name_list</code> elements.
5246             If the optional <code class="varname">namelist</code> is specified
5247             with <span><strong class="command">except-from</strong></span>, records whose query name
5248             matches the list will be accepted regardless of the filter
5249             setting.
5250             Likewise, if the alias name is a subdomain of the
5251             corresponding zone, the <span><strong class="command">deny-answer-aliases</strong></span>
5252             filter will not apply;
5253             for example, even if "example.com" is specified for
5254             <span><strong class="command">deny-answer-aliases</strong></span>,
5255           </p>
5256 <pre class="programlisting">www.example.com. CNAME xxx.example.com.</pre>
5257 <p>
5258             returned by an "example.com" server will be accepted.
5259           </p>
5260 <p>
5261             In the <code class="varname">address_match_list</code> of the
5262             <span><strong class="command">deny-answer-addresses</strong></span> option, only
5263             <code class="varname">ip_addr</code>
5264             and <code class="varname">ip_prefix</code>
5265             are meaningful;
5266             any <code class="varname">key_id</code> will be silently ignored.
5267           </p>
5268 <p>
5269             If a response message is rejected due to the filtering,
5270             the entire message is discarded without being cached, and
5271             a SERVFAIL error will be returned to the client.
5272           </p>
5273 <p>
5274             This filtering is intended to prevent "DNS rebinding attacks," in
5275             which an attacker, in response to a query for a domain name the
5276             attacker controls, returns an IP address within your own network or
5277             an alias name within your own domain.
5278             A naive web browser or script could then serve as an
5279             unintended proxy, allowing the attacker
5280             to get access to an internal node of your local network
5281             that couldn't be externally accessed otherwise.
5282             See the paper available at
5283             <a href="" target="_top">
5284             http://portal.acm.org/citation.cfm?id=1315245.1315298
5285             </a>
5286             for more details about the attacks.
5287           </p>
5288 <p>
5289             For example, if you own a domain named "example.net" and
5290             your internal network uses an IPv4 prefix 192.0.2.0/24,
5291             you might specify the following rules:
5292           </p>
5293 <pre class="programlisting">deny-answer-addresses { 192.0.2.0/24; } except-from { "example.net"; };
5294 deny-answer-aliases { "example.net"; };
5295 </pre>
5296 <p>
5297             If an external attacker lets a web browser in your local
5298             network look up an IPv4 address of "attacker.example.com",
5299             the attacker's DNS server would return a response like this:
5300           </p>
5301 <pre class="programlisting">attacker.example.com. A 192.0.2.1</pre>
5302 <p>
5303             in the answer section.
5304             Since the rdata of this record (the IPv4 address) matches
5305             the specified prefix 192.0.2.0/24, this response will be
5306             ignored.
5307           </p>
5308 <p>
5309             On the other hand, if the browser looks up a legitimate
5310             internal web server "www.example.net" and the
5311             following response is returned to
5312             the <acronym class="acronym">BIND</acronym> 9 server
5313           </p>
5314 <pre class="programlisting">www.example.net. A 192.0.2.2</pre>
5315 <p>
5316             it will be accepted since the owner name "www.example.net"
5317             matches the <span><strong class="command">except-from</strong></span> element,
5318             "example.net".
5319           </p>
5320 <p>
5321             Note that this is not really an attack on the DNS per se.
5322             In fact, there is nothing wrong for an "external" name to
5323             be mapped to your "internal" IP address or domain name
5324             from the DNS point of view.
5325             It might actually be provided for a legitimate purpose,
5326             such as for debugging.
5327             As long as the mapping is provided by the correct owner,
5328             it is not possible or does not make sense to detect
5329             whether the intent of the mapping is legitimate or not
5330             within the DNS.
5331             The "rebinding" attack must primarily be protected at the
5332             application that uses the DNS.
5333             For a large site, however, it may be difficult to protect
5334             all possible applications at once.
5335             This filtering feature is provided only to help such an
5336             operational environment;
5337             it is generally discouraged to turn it on unless you are
5338             very sure you have no other choice and the attack is a
5339             real threat for your applications.
5340           </p>
5341 <p>
5342             Care should be particularly taken if you want to use this
5343             option for addresses within 127.0.0.0/8.
5344             These addresses are obviously "internal", but many
5345             applications conventionally rely on a DNS mapping from
5346             some name to such an address.
5347             Filtering out DNS records containing this address
5348             spuriously can break such applications.
5349           </p>
5350 </div>
5351 </div>
5352 <div class="sect2" lang="en">
5353 <div class="titlepage"><div><div><h3 class="title">
5354 <a name="server_statement_grammar"></a><span><strong class="command">server</strong></span> Statement Grammar</h3></div></div></div>
5355 <pre class="programlisting"><span><strong class="command">server</strong></span> <em class="replaceable"><code>ip_addr[/prefixlen]</code></em> {
5356     [<span class="optional"> bogus <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5357     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5358     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5359     [<span class="optional"> edns <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5360     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
5361     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
5362     [<span class="optional"> transfers <em class="replaceable"><code>number</code></em> ; </span>]
5363     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em> ; ]</span>]
5364     [<span class="optional"> keys <em class="replaceable"><code>{ string ; [<span class="optional"> string ; [<span class="optional">...</span>]</span>] }</code></em> ; </span>]
5365     [<span class="optional"> transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
5366     [<span class="optional"> transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
5367     [<span class="optional"> notify-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
5368     [<span class="optional"> notify-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
5369     [<span class="optional"> query-source [<span class="optional"> address ( <em class="replaceable"><code>ip_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
5370                   [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]; </span>]
5371     [<span class="optional"> query-source-v6 [<span class="optional"> address ( <em class="replaceable"><code>ip_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
5372                      [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]; </span>]
5373     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5374     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
5375     [<span class="optional"> queryport-pool-updateinterval <em class="replaceable"><code>number</code></em>; </span>]
5376 };
5377 </pre>
5378 </div>
5379 <div class="sect2" lang="en">
5380 <div class="titlepage"><div><div><h3 class="title">
5381 <a name="server_statement_definition_and_usage"></a><span><strong class="command">server</strong></span> Statement Definition and
5382             Usage</h3></div></div></div>
5383 <p>
5384             The <span><strong class="command">server</strong></span> statement defines
5385             characteristics
5386             to be associated with a remote name server.  If a prefix length is
5387             specified, then a range of servers is covered.  Only the most
5388             specific
5389             server clause applies regardless of the order in
5390             <code class="filename">named.conf</code>.
5391           </p>
5392 <p>
5393             The <span><strong class="command">server</strong></span> statement can occur at
5394             the top level of the
5395             configuration file or inside a <span><strong class="command">view</strong></span>
5396             statement.
5397             If a <span><strong class="command">view</strong></span> statement contains
5398             one or more <span><strong class="command">server</strong></span> statements, only
5399             those
5400             apply to the view and any top-level ones are ignored.
5401             If a view contains no <span><strong class="command">server</strong></span>
5402             statements,
5403             any top-level <span><strong class="command">server</strong></span> statements are
5404             used as
5405             defaults.
5406           </p>
5407 <p>
5408             If you discover that a remote server is giving out bad data,
5409             marking it as bogus will prevent further queries to it. The
5410             default
5411             value of <span><strong class="command">bogus</strong></span> is <span><strong class="command">no</strong></span>.
5412           </p>
5413 <p>
5414             The <span><strong class="command">provide-ixfr</strong></span> clause determines
5415             whether
5416             the local server, acting as master, will respond with an
5417             incremental
5418             zone transfer when the given remote server, a slave, requests it.
5419             If set to <span><strong class="command">yes</strong></span>, incremental transfer
5420             will be provided
5421             whenever possible. If set to <span><strong class="command">no</strong></span>,
5422             all transfers
5423             to the remote server will be non-incremental. If not set, the
5424             value
5425             of the <span><strong class="command">provide-ixfr</strong></span> option in the
5426             view or
5427             global options block is used as a default.
5428           </p>
5429 <p>
5430             The <span><strong class="command">request-ixfr</strong></span> clause determines
5431             whether
5432             the local server, acting as a slave, will request incremental zone
5433             transfers from the given remote server, a master. If not set, the
5434             value of the <span><strong class="command">request-ixfr</strong></span> option in
5435             the view or
5436             global options block is used as a default.
5437           </p>
5438 <p>
5439             IXFR requests to servers that do not support IXFR will
5440             automatically
5441             fall back to AXFR.  Therefore, there is no need to manually list
5442             which servers support IXFR and which ones do not; the global
5443             default
5444             of <span><strong class="command">yes</strong></span> should always work.
5445             The purpose of the <span><strong class="command">provide-ixfr</strong></span> and
5446             <span><strong class="command">request-ixfr</strong></span> clauses is
5447             to make it possible to disable the use of IXFR even when both
5448             master
5449             and slave claim to support it, for example if one of the servers
5450             is buggy and crashes or corrupts data when IXFR is used.
5451           </p>
5452 <p>
5453             The <span><strong class="command">edns</strong></span> clause determines whether
5454             the local server will attempt to use EDNS when communicating
5455             with the remote server.  The default is <span><strong class="command">yes</strong></span>.
5456           </p>
5457 <p>
5458             The <span><strong class="command">edns-udp-size</strong></span> option sets the EDNS UDP size
5459             that is advertised by <span><strong class="command">named</strong></span> when querying the remote server.
5460             Valid values are 512 to 4096 bytes (values outside this range will be
5461             silently adjusted).  This option is useful when you wish to
5462             advertises a different value to this server than the value you
5463             advertise globally, for example, when there is a firewall at the
5464             remote site that is blocking large replies.
5465           </p>
5466 <p>
5467             The <span><strong class="command">max-udp-size</strong></span> option sets the
5468             maximum EDNS UDP message size <span><strong class="command">named</strong></span> will send.  Valid
5469             values are 512 to 4096 bytes (values outside this range will
5470             be silently adjusted).  This option is useful when you
5471             know that there is a firewall that is blocking large
5472             replies from <span><strong class="command">named</strong></span>.
5473           </p>
5474 <p>
5475             The server supports two zone transfer methods. The first, <span><strong class="command">one-answer</strong></span>,
5476             uses one DNS message per resource record transferred. <span><strong class="command">many-answers</strong></span> packs
5477             as many resource records as possible into a message. <span><strong class="command">many-answers</strong></span> is
5478             more efficient, but is only known to be understood by <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
5479             8.x, and patched versions of <acronym class="acronym">BIND</acronym>
5480             4.9.5. You can specify which method
5481             to use for a server with the <span><strong class="command">transfer-format</strong></span> option.
5482             If <span><strong class="command">transfer-format</strong></span> is not
5483             specified, the <span><strong class="command">transfer-format</strong></span>
5484             specified
5485             by the <span><strong class="command">options</strong></span> statement will be
5486             used.
5487           </p>
5488 <p><span><strong class="command">transfers</strong></span>
5489             is used to limit the number of concurrent inbound zone
5490             transfers from the specified server. If no
5491             <span><strong class="command">transfers</strong></span> clause is specified, the
5492             limit is set according to the
5493             <span><strong class="command">transfers-per-ns</strong></span> option.
5494           </p>
5495 <p>
5496             The <span><strong class="command">keys</strong></span> clause identifies a
5497             <span><strong class="command">key_id</strong></span> defined by the <span><strong class="command">key</strong></span> statement,
5498             to be used for transaction security (TSIG, <a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
5499             when talking to the remote server.
5500             When a request is sent to the remote server, a request signature
5501             will be generated using the key specified here and appended to the
5502             message. A request originating from the remote server is not
5503             required
5504             to be signed by this key.
5505           </p>
5506 <p>
5507             Although the grammar of the <span><strong class="command">keys</strong></span>
5508             clause
5509             allows for multiple keys, only a single key per server is
5510             currently
5511             supported.
5512           </p>
5513 <p>
5514             The <span><strong class="command">transfer-source</strong></span> and
5515             <span><strong class="command">transfer-source-v6</strong></span> clauses specify
5516             the IPv4 and IPv6 source
5517             address to be used for zone transfer with the remote server,
5518             respectively.
5519             For an IPv4 remote server, only <span><strong class="command">transfer-source</strong></span> can
5520             be specified.
5521             Similarly, for an IPv6 remote server, only
5522             <span><strong class="command">transfer-source-v6</strong></span> can be
5523             specified.
5524             For more details, see the description of
5525             <span><strong class="command">transfer-source</strong></span> and
5526             <span><strong class="command">transfer-source-v6</strong></span> in
5527             <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
5528           </p>
5529 <p>
5530             The <span><strong class="command">notify-source</strong></span> and
5531             <span><strong class="command">notify-source-v6</strong></span> clauses specify the
5532             IPv4 and IPv6 source address to be used for notify
5533             messages sent to remote servers, respectively.  For an
5534             IPv4 remote server, only <span><strong class="command">notify-source</strong></span>
5535             can be specified.  Similarly, for an IPv6 remote server,
5536             only <span><strong class="command">notify-source-v6</strong></span> can be specified.
5537           </p>
5538 <p>
5539             The <span><strong class="command">query-source</strong></span> and
5540             <span><strong class="command">query-source-v6</strong></span> clauses specify the
5541             IPv4 and IPv6 source address to be used for queries
5542             sent to remote servers, respectively.  For an IPv4
5543             remote server, only <span><strong class="command">query-source</strong></span> can
5544             be specified.  Similarly, for an IPv6 remote server,
5545             only <span><strong class="command">query-source-v6</strong></span> can be specified.
5546           </p>
5547 </div>
5548 <div class="sect2" lang="en">
5549 <div class="titlepage"><div><div><h3 class="title">
5550 <a name="statschannels"></a><span><strong class="command">statistics-channels</strong></span> Statement Grammar</h3></div></div></div>
5551 <pre class="programlisting"><span><strong class="command">statistics-channels</strong></span> {
5552    [ inet ( ip_addr | * ) [ port ip_port ]
5553    [ allow { <em class="replaceable"><code> address_match_list </code></em> } ]; ]
5554    [ inet ...; ]
5555 };
5556 </pre>
5557 </div>
5558 <div class="sect2" lang="en">
5559 <div class="titlepage"><div><div><h3 class="title">
5560 <a name="id2588166"></a><span><strong class="command">statistics-channels</strong></span> Statement Definition and
5561             Usage</h3></div></div></div>
5562 <p>
5563           The <span><strong class="command">statistics-channels</strong></span> statement
5564           declares communication channels to be used by system
5565           administrators to get access to statistics information of
5566           the name server.
5567         </p>
5568 <p>
5569           This statement intends to be flexible to support multiple
5570           communication protocols in the future, but currently only
5571           HTTP access is supported.
5572           It requires that BIND 9 be compiled with libxml2;
5573           the <span><strong class="command">statistics-channels</strong></span> statement is
5574           still accepted even if it is built without the library,
5575           but any HTTP access will fail with an error.
5576         </p>
5577 <p>
5578           An <span><strong class="command">inet</strong></span> control channel is a TCP socket
5579           listening at the specified <span><strong class="command">ip_port</strong></span> on the
5580           specified <span><strong class="command">ip_addr</strong></span>, which can be an IPv4 or IPv6
5581           address.  An <span><strong class="command">ip_addr</strong></span> of <code class="literal">*</code> (asterisk) is
5582           interpreted as the IPv4 wildcard address; connections will be
5583           accepted on any of the system's IPv4 addresses.
5584           To listen on the IPv6 wildcard address,
5585           use an <span><strong class="command">ip_addr</strong></span> of <code class="literal">::</code>.
5586         </p>
5587 <p>
5588           If no port is specified, port 80 is used for HTTP channels.
5589           The asterisk "<code class="literal">*</code>" cannot be used for
5590           <span><strong class="command">ip_port</strong></span>.
5591         </p>
5592 <p>
5593           The attempt of opening a statistics channel is
5594           restricted by the optional <span><strong class="command">allow</strong></span> clause.
5595           Connections to the statistics channel are permitted based on the
5596           <span><strong class="command">address_match_list</strong></span>.
5597           If no <span><strong class="command">allow</strong></span> clause is present,
5598           <span><strong class="command">named</strong></span> accepts connection
5599           attempts from any address; since the statistics may
5600           contain sensitive internal information, it is highly
5601           recommended to restrict the source of connection requests
5602           appropriately.
5603         </p>
5604 <p>
5605           If no <span><strong class="command">statistics-channels</strong></span> statement is present,
5606           <span><strong class="command">named</strong></span> will not open any communication channels.
5607         </p>
5608 </div>
5609 <div class="sect2" lang="en">
5610 <div class="titlepage"><div><div><h3 class="title">
5611 <a name="trusted-keys"></a><span><strong class="command">trusted-keys</strong></span> Statement Grammar</h3></div></div></div>
5612 <pre class="programlisting"><span><strong class="command">trusted-keys</strong></span> {
5613     <em class="replaceable"><code>string</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ;
5614     [<span class="optional"> <em class="replaceable"><code>string</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ; [<span class="optional">...</span>]</span>]
5615 };
5616 </pre>
5617 </div>
5618 <div class="sect2" lang="en">
5619 <div class="titlepage"><div><div><h3 class="title">
5620 <a name="id2588374"></a><span><strong class="command">trusted-keys</strong></span> Statement Definition
5621             and Usage</h3></div></div></div>
5622 <p>
5623             The <span><strong class="command">trusted-keys</strong></span> statement defines
5624             DNSSEC security roots. DNSSEC is described in <a href="Bv9ARM.ch04.html#DNSSEC" title="DNSSEC">the section called &#8220;DNSSEC&#8221;</a>. A security root is defined when the
5625             public key for a non-authoritative zone is known, but
5626             cannot be securely obtained through DNS, either because
5627             it is the DNS root zone or because its parent zone is
5628             unsigned.  Once a key has been configured as a trusted
5629             key, it is treated as if it had been validated and
5630             proven secure. The resolver attempts DNSSEC validation
5631             on all DNS data in subdomains of a security root.
5632           </p>
5633 <p>
5634             All keys (and corresponding zones) listed in
5635             <span><strong class="command">trusted-keys</strong></span> are deemed to exist regardless
5636             of what parent zones say.  Similarly for all keys listed in
5637             <span><strong class="command">trusted-keys</strong></span> only those keys are
5638             used to validate the DNSKEY RRset.  The parent's DS RRset
5639             will not be used.
5640           </p>
5641 <p>
5642             The <span><strong class="command">trusted-keys</strong></span> statement can contain
5643             multiple key entries, each consisting of the key's
5644             domain name, flags, protocol, algorithm, and the Base-64
5645             representation of the key data.
5646             Spaces, tabs, newlines and carriage returns are ignored
5647             in the key data, so the configuration may be split up into
5648             multiple lines.
5649           </p>
5650 <p>
5651             <span><strong class="command">trusted-keys</strong></span> may be set at the top level
5652             of <code class="filename">named.conf</code> or within a view.  If it is
5653             set in both places, they are additive: keys defined at the top
5654             level are inherited by all views, but keys defined in a view
5655             are only used within that view.
5656           </p>
5657 </div>
5658 <div class="sect2" lang="en">
5659 <div class="titlepage"><div><div><h3 class="title">
5660 <a name="id2588421"></a><span><strong class="command">managed-keys</strong></span> Statement Grammar</h3></div></div></div>
5661 <pre class="programlisting"><span><strong class="command">managed-keys</strong></span> {
5662     <em class="replaceable"><code>string</code></em> initial-key <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ;
5663     [<span class="optional"> <em class="replaceable"><code>string</code></em> initial-key <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ; [<span class="optional">...</span>]</span>]
5664 };
5665 </pre>
5666 </div>
5667 <div class="sect2" lang="en">
5668 <div class="titlepage"><div><div><h3 class="title">
5669 <a name="managed-keys"></a><span><strong class="command">managed-keys</strong></span> Statement Definition
5670             and Usage</h3></div></div></div>
5671 <p>
5672             The <span><strong class="command">managed-keys</strong></span> statement, like
5673             <span><strong class="command">trusted-keys</strong></span>, defines DNSSEC
5674             security roots.  The difference is that
5675             <span><strong class="command">managed-keys</strong></span> can be kept up to date
5676             automatically, without intervention from the resolver
5677             operator.
5678           </p>
5679 <p>
5680             Suppose, for example, that a zone's key-signing
5681             key was compromised, and the zone owner had to revoke and
5682             replace the key.  A resolver which had the old key in a
5683             <span><strong class="command">trusted-keys</strong></span> statement would be
5684             unable to validate this zone any longer; it would
5685             reply with a SERVFAIL response code.  This would
5686             continue until the resolver operator had updated the
5687             <span><strong class="command">trusted-keys</strong></span> statement with the new key.
5688           </p>
5689 <p>
5690             If, however, the zone were listed in a
5691             <span><strong class="command">managed-keys</strong></span> statement instead, then the
5692             zone owner could add a "stand-by" key to the zone in advance.
5693             <span><strong class="command">named</strong></span> would store the stand-by key, and
5694             when the original key was revoked, <span><strong class="command">named</strong></span>
5695             would be able to transition smoothly to the new key.  It would
5696             also recognize that the old key had been revoked, and cease
5697             using that key to validate answers, minimizing the damage that
5698             the compromised key could do.
5699           </p>
5700 <p>
5701             A <span><strong class="command">managed-keys</strong></span> statement contains a list of
5702             the keys to be managed, along with information about how the
5703             keys are to be initialized for the first time.  The only
5704             initialization method currently supported (as of
5705             <acronym class="acronym">BIND</acronym> 9.7.0) is <code class="literal">initial-key</code>.
5706             This means the <span><strong class="command">managed-keys</strong></span> statement must
5707             contain a copy of the initializing key.  (Future releases may
5708             allow keys to be initialized by other methods, eliminating this
5709             requirement.)
5710           </p>
5711 <p>
5712             Consequently, a <span><strong class="command">managed-keys</strong></span> statement
5713             appears similar to a <span><strong class="command">trusted-keys</strong></span>, differing
5714             in the presence of the second field, containing the keyword
5715             <code class="literal">initial-key</code>.  The difference is, whereas the
5716             keys listed in a <span><strong class="command">trusted-keys</strong></span> continue to be
5717             trusted until they are removed from
5718             <code class="filename">named.conf</code>, an initializing key listed
5719             in a <span><strong class="command">managed-keys</strong></span> statement is only trusted
5720             <span class="emphasis"><em>once</em></span>: for as long as it takes to load the
5721             managed key database and start the RFC 5011 key maintenance
5722             process.
5723           </p>
5724 <p>
5725             The first time <span><strong class="command">named</strong></span> runs with a managed key
5726             configured in <code class="filename">named.conf</code>, it fetches the
5727             DNSKEY RRset directly from the zone apex, and validates it
5728             using the key specified in the <span><strong class="command">managed-keys</strong></span>
5729             statement.  If the DNSKEY RRset is validly signed, then it is
5730             used as the basis for a new managed keys database.
5731           </p>
5732 <p>
5733             From that point on, whenever <span><strong class="command">named</strong></span> runs, it
5734             sees the <span><strong class="command">managed-keys</strong></span> statement, checks to
5735             make sure RFC 5011 key maintenance has already been initialized
5736             for the specified domain, and if so, it simply moves on.  The
5737             key specified in the <span><strong class="command">managed-keys</strong></span> is not
5738             used to validate answers; it has been superseded by the key or
5739             keys stored in the managed keys database.
5740           </p>
5741 <p>
5742             The next time <span><strong class="command">named</strong></span> runs after a name
5743             has been <span class="emphasis"><em>removed</em></span> from the
5744             <span><strong class="command">managed-keys</strong></span> statement, the corresponding
5745             zone will be removed from the managed keys database,
5746             and RFC 5011 key maintenance will no longer be used for that
5747             domain.
5748           </p>
5749 <p>
5750             <span><strong class="command">named</strong></span> only maintains a single managed keys
5751             database; consequently, unlike <span><strong class="command">trusted-keys</strong></span>,
5752             <span><strong class="command">managed-keys</strong></span> may only be set at the top
5753             level of <code class="filename">named.conf</code>, not within a view.
5754           </p>
5755 <p>
5756             In the current implementation, the managed keys database is
5757             stored as a master-format zone file called
5758             <code class="filename">managed-keys.bind</code>.  When the key database
5759             is changed, the zone is updated.  As with any other dynamic
5760             zone, changes will be written into a journal file,
5761             <code class="filename">managed-keys.bind.jnl</code>.  They are committed
5762             to the master file as soon as possible afterward; in the case
5763             of the managed key database, this will usually occur within 30
5764             seconds.  So, whenever <span><strong class="command">named</strong></span> is using
5765             automatic key maintenace, those two files can be expected to
5766             exist in the working directory.  (For this reason among others,
5767             the working directory should be always be writable by
5768             <span><strong class="command">named</strong></span>.)
5769           </p>
5770 <p>
5771             If the <span><strong class="command">dnssec-lookaside</strong></span> option is
5772             set to <strong class="userinput"><code>auto</code></strong>, <span><strong class="command">named</strong></span>
5773             will automatically initialize a managed key for the
5774             zone <code class="literal">dlv.isc.org</code>.  The key that is
5775             used to initialize the key maintenance process is built
5776             into <span><strong class="command">named</strong></span>, and can be overridden
5777             from <span><strong class="command">bindkeys-file</strong></span>.
5778           </p>
5779 </div>
5780 <div class="sect2" lang="en">
5781 <div class="titlepage"><div><div><h3 class="title">
5782 <a name="view_statement_grammar"></a><span><strong class="command">view</strong></span> Statement Grammar</h3></div></div></div>
5783 <pre class="programlisting"><span><strong class="command">view</strong></span> <em class="replaceable"><code>view_name</code></em>
5784       [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
5785       match-clients { <em class="replaceable"><code>address_match_list</code></em> };
5786       match-destinations { <em class="replaceable"><code>address_match_list</code></em> };
5787       match-recursive-only <em class="replaceable"><code>yes_or_no</code></em> ;
5788       [<span class="optional"> <em class="replaceable"><code>view_option</code></em>; ...</span>]
5789       [<span class="optional"> <em class="replaceable"><code>zone_statement</code></em>; ...</span>]
5790 };
5791 </pre>
5792 </div>
5793 <div class="sect2" lang="en">
5794 <div class="titlepage"><div><div><h3 class="title">
5795 <a name="id2588915"></a><span><strong class="command">view</strong></span> Statement Definition and Usage</h3></div></div></div>
5796 <p>
5797             The <span><strong class="command">view</strong></span> statement is a powerful
5798             feature
5799             of <acronym class="acronym">BIND</acronym> 9 that lets a name server
5800             answer a DNS query differently
5801             depending on who is asking. It is particularly useful for
5802             implementing
5803             split DNS setups without having to run multiple servers.
5804           </p>
5805 <p>
5806             Each <span><strong class="command">view</strong></span> statement defines a view
5807             of the
5808             DNS namespace that will be seen by a subset of clients.  A client
5809             matches
5810             a view if its source IP address matches the
5811             <code class="varname">address_match_list</code> of the view's
5812             <span><strong class="command">match-clients</strong></span> clause and its
5813             destination IP address matches
5814             the <code class="varname">address_match_list</code> of the
5815             view's
5816             <span><strong class="command">match-destinations</strong></span> clause.  If not
5817             specified, both
5818             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
5819             default to matching all addresses.  In addition to checking IP
5820             addresses
5821             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
5822             can also take <span><strong class="command">keys</strong></span> which provide an
5823             mechanism for the
5824             client to select the view.  A view can also be specified
5825             as <span><strong class="command">match-recursive-only</strong></span>, which
5826             means that only recursive
5827             requests from matching clients will match that view.
5828             The order of the <span><strong class="command">view</strong></span> statements is
5829             significant &#8212;
5830             a client request will be resolved in the context of the first
5831             <span><strong class="command">view</strong></span> that it matches.
5832           </p>
5833 <p>
5834             Zones defined within a <span><strong class="command">view</strong></span>
5835             statement will
5836             only be accessible to clients that match the <span><strong class="command">view</strong></span>.
5837             By defining a zone of the same name in multiple views, different
5838             zone data can be given to different clients, for example,
5839             "internal"
5840             and "external" clients in a split DNS setup.
5841           </p>
5842 <p>
5843             Many of the options given in the <span><strong class="command">options</strong></span> statement
5844             can also be used within a <span><strong class="command">view</strong></span>
5845             statement, and then
5846             apply only when resolving queries with that view.  When no
5847             view-specific
5848             value is given, the value in the <span><strong class="command">options</strong></span> statement
5849             is used as a default.  Also, zone options can have default values
5850             specified
5851             in the <span><strong class="command">view</strong></span> statement; these
5852             view-specific defaults
5853             take precedence over those in the <span><strong class="command">options</strong></span> statement.
5854           </p>
5855 <p>
5856             Views are class specific.  If no class is given, class IN
5857             is assumed.  Note that all non-IN views must contain a hint zone,
5858             since only the IN class has compiled-in default hints.
5859           </p>
5860 <p>
5861             If there are no <span><strong class="command">view</strong></span> statements in
5862             the config
5863             file, a default view that matches any client is automatically
5864             created
5865             in class IN. Any <span><strong class="command">zone</strong></span> statements
5866             specified on
5867             the top level of the configuration file are considered to be part
5868             of
5869             this default view, and the <span><strong class="command">options</strong></span>
5870             statement will
5871             apply to the default view. If any explicit <span><strong class="command">view</strong></span>
5872             statements are present, all <span><strong class="command">zone</strong></span>
5873             statements must
5874             occur inside <span><strong class="command">view</strong></span> statements.
5875           </p>
5876 <p>
5877             Here is an example of a typical split DNS setup implemented
5878             using <span><strong class="command">view</strong></span> statements:
5879           </p>
5880 <pre class="programlisting">view "internal" {
5881       // This should match our internal networks.
5882       match-clients { 10.0.0.0/8; };
5883
5884       // Provide recursive service to internal
5885       // clients only.
5886       recursion yes;
5887
5888       // Provide a complete view of the example.com
5889       // zone including addresses of internal hosts.
5890       zone "example.com" {
5891             type master;
5892             file "example-internal.db";
5893       };
5894 };
5895
5896 view "external" {
5897       // Match all clients not matched by the
5898       // previous view.
5899       match-clients { any; };
5900
5901       // Refuse recursive service to external clients.
5902       recursion no;
5903
5904       // Provide a restricted view of the example.com
5905       // zone containing only publicly accessible hosts.
5906       zone "example.com" {
5907            type master;
5908            file "example-external.db";
5909       };
5910 };
5911 </pre>
5912 </div>
5913 <div class="sect2" lang="en">
5914 <div class="titlepage"><div><div><h3 class="title">
5915 <a name="zone_statement_grammar"></a><span><strong class="command">zone</strong></span>
5916             Statement Grammar</h3></div></div></div>
5917 <pre class="programlisting"><span><strong class="command">zone</strong></span> <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
5918     type master;
5919     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5920     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5921     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5922     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5923     [<span class="optional"> update-policy <em class="replaceable"><code>local</code></em> | { <em class="replaceable"><code>update_policy_rule</code></em> [<span class="optional">...</span>] }; </span>]
5924     [<span class="optional"> also-notify { <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ;
5925                   [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; ... </span>] }; </span>]
5926     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
5927     [<span class="optional"> check-mx (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
5928     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5929     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5930     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
5931     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
5932     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
5933     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
5934     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
5935     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
5936     [<span class="optional"> forwarders { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; ... </span>] }; </span>]
5937     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
5938     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5939     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
5940     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5941     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
5942     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
5943     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
5944     [<span class="optional"> notify <em class="replaceable"><code>yes_or_no</code></em> | <em class="replaceable"><code>explicit</code></em> | <em class="replaceable"><code>master-only</code></em> ; </span>]
5945     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
5946     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5947     [<span class="optional"> pubkey <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ; </span>]
5948     [<span class="optional"> notify-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
5949     [<span class="optional"> notify-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
5950     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5951     [<span class="optional"> sig-validity-interval <em class="replaceable"><code>number</code></em> [<span class="optional"><em class="replaceable"><code>number</code></em></span>] ; </span>]
5952     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
5953     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
5954     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
5955     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
5956     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
5957     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
5958     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
5959     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
5960     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
5961     [<span class="optional"> auto-dnssec <code class="constant">allow</code>|<code class="constant">maintain</code>|<code class="constant">create</code>|<code class="constant">off</code>; </span>]
5962     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5963 };
5964
5965 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
5966     type slave;
5967     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5968     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5969     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5970     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5971     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5972     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5973     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5974     [<span class="optional"> dnssec-secure-to-insecure <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5975     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5976     [<span class="optional"> also-notify { <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ;
5977                   [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; ... </span>] }; </span>]
5978     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
5979     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
5980     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
5981     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
5982     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
5983     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
5984     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
5985     [<span class="optional"> forwarders { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; ... </span>] }; </span>]
5986     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
5987     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5988     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
5989     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5990     [<span class="optional"> masters [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] { ( <em class="replaceable"><code>masters_list</code></em> | <em class="replaceable"><code>ip_addr</code></em>
5991                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
5992                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
5993     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
5994     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
5995     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
5996     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
5997     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
5998     [<span class="optional"> notify <em class="replaceable"><code>yes_or_no</code></em> | <em class="replaceable"><code>explicit</code></em> | <em class="replaceable"><code>master-only</code></em> ; </span>]
5999     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
6000     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6001     [<span class="optional"> pubkey <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ; </span>]
6002     [<span class="optional"> transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6003     [<span class="optional"> transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6004     [<span class="optional"> alt-transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6005     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
6006                              [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6007     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6008     [<span class="optional"> notify-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6009     [<span class="optional"> notify-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6010     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6011     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
6012     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
6013     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
6014     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
6015     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
6016     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6017     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6018 };
6019
6020 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6021     type hint;
6022     file <em class="replaceable"><code>string</code></em> ;
6023     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6024     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>] // Not Implemented.
6025 };
6026
6027 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6028     type stub;
6029     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6030     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6031     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
6032     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
6033     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6034     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
6035     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
6036     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
6037     [<span class="optional"> forwarders { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; ... </span>] }; </span>]
6038     [<span class="optional"> masters [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] { ( <em class="replaceable"><code>masters_list</code></em> | <em class="replaceable"><code>ip_addr</code></em>
6039                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
6040                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
6041     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
6042     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
6043     [<span class="optional"> pubkey <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ; </span>]
6044     [<span class="optional"> transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6045     [<span class="optional"> transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
6046                          [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6047     [<span class="optional"> alt-transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6048     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
6049                             [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6050     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6051     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6052     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
6053     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
6054     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
6055     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
6056     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
6057     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6058 };
6059
6060 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6061     type forward;
6062     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
6063     [<span class="optional"> forwarders { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; ... </span>] }; </span>]
6064     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6065 };
6066
6067 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6068     type delegation-only;
6069 };
6070
6071 </pre>
6072 </div>
6073 <div class="sect2" lang="en">
6074 <div class="titlepage"><div><div><h3 class="title">
6075 <a name="id2590556"></a><span><strong class="command">zone</strong></span> Statement Definition and Usage</h3></div></div></div>
6076 <div class="sect3" lang="en">
6077 <div class="titlepage"><div><div><h4 class="title">
6078 <a name="id2590564"></a>Zone Types</h4></div></div></div>
6079 <div class="informaltable"><table border="1">
6080 <colgroup>
6081 <col>
6082 <col>
6083 </colgroup>
6084 <tbody>
6085 <tr>
6086 <td>
6087                       <p>
6088                         <code class="varname">master</code>
6089                       </p>
6090                     </td>
6091 <td>
6092                       <p>
6093                         The server has a master copy of the data
6094                         for the zone and will be able to provide authoritative
6095                         answers for
6096                         it.
6097                       </p>
6098                     </td>
6099 </tr>
6100 <tr>
6101 <td>
6102                       <p>
6103                         <code class="varname">slave</code>
6104                       </p>
6105                     </td>
6106 <td>
6107                       <p>
6108                         A slave zone is a replica of a master
6109                         zone. The <span><strong class="command">masters</strong></span> list
6110                         specifies one or more IP addresses
6111                         of master servers that the slave contacts to update
6112                         its copy of the zone.
6113                         Masters list elements can also be names of other
6114                         masters lists.
6115                         By default, transfers are made from port 53 on the
6116                         servers; this can
6117                         be changed for all servers by specifying a port number
6118                         before the
6119                         list of IP addresses, or on a per-server basis after
6120                         the IP address.
6121                         Authentication to the master can also be done with
6122                         per-server TSIG keys.
6123                         If a file is specified, then the
6124                         replica will be written to this file whenever the zone
6125                         is changed,
6126                         and reloaded from this file on a server restart. Use
6127                         of a file is
6128                         recommended, since it often speeds server startup and
6129                         eliminates
6130                         a needless waste of bandwidth. Note that for large
6131                         numbers (in the
6132                         tens or hundreds of thousands) of zones per server, it
6133                         is best to
6134                         use a two-level naming scheme for zone filenames. For
6135                         example,
6136                         a slave server for the zone <code class="literal">example.com</code> might place
6137                         the zone contents into a file called
6138                         <code class="filename">ex/example.com</code> where <code class="filename">ex/</code> is
6139                         just the first two letters of the zone name. (Most
6140                         operating systems
6141                         behave very slowly if you put 100000 files into
6142                         a single directory.)
6143                       </p>
6144                     </td>
6145 </tr>
6146 <tr>
6147 <td>
6148                       <p>
6149                         <code class="varname">stub</code>
6150                       </p>
6151                     </td>
6152 <td>
6153                       <p>
6154                         A stub zone is similar to a slave zone,
6155                         except that it replicates only the NS records of a
6156                         master zone instead
6157                         of the entire zone. Stub zones are not a standard part
6158                         of the DNS;
6159                         they are a feature specific to the <acronym class="acronym">BIND</acronym> implementation.
6160                       </p>
6161
6162                       <p>
6163                         Stub zones can be used to eliminate the need for glue
6164                         NS record
6165                         in a parent zone at the expense of maintaining a stub
6166                         zone entry and
6167                         a set of name server addresses in <code class="filename">named.conf</code>.
6168                         This usage is not recommended for new configurations,
6169                         and BIND 9
6170                         supports it only in a limited way.
6171                         In <acronym class="acronym">BIND</acronym> 4/8, zone
6172                         transfers of a parent zone
6173                         included the NS records from stub children of that
6174                         zone. This meant
6175                         that, in some cases, users could get away with
6176                         configuring child stubs
6177                         only in the master server for the parent zone. <acronym class="acronym">BIND</acronym>
6178                         9 never mixes together zone data from different zones
6179                         in this
6180                         way. Therefore, if a <acronym class="acronym">BIND</acronym> 9 master serving a parent
6181                         zone has child stub zones configured, all the slave
6182                         servers for the
6183                         parent zone also need to have the same child stub
6184                         zones
6185                         configured.
6186                       </p>
6187
6188                       <p>
6189                         Stub zones can also be used as a way of forcing the
6190                         resolution
6191                         of a given domain to use a particular set of
6192                         authoritative servers.
6193                         For example, the caching name servers on a private
6194                         network using
6195                         RFC1918 addressing may be configured with stub zones
6196                         for
6197                         <code class="literal">10.in-addr.arpa</code>
6198                         to use a set of internal name servers as the
6199                         authoritative
6200                         servers for that domain.
6201                       </p>
6202                     </td>
6203 </tr>
6204 <tr>
6205 <td>
6206                       <p>
6207                         <code class="varname">forward</code>
6208                       </p>
6209                     </td>
6210 <td>
6211                       <p>
6212                         A "forward zone" is a way to configure
6213                         forwarding on a per-domain basis.  A <span><strong class="command">zone</strong></span> statement
6214                         of type <span><strong class="command">forward</strong></span> can
6215                         contain a <span><strong class="command">forward</strong></span>
6216                         and/or <span><strong class="command">forwarders</strong></span>
6217                         statement,
6218                         which will apply to queries within the domain given by
6219                         the zone
6220                         name. If no <span><strong class="command">forwarders</strong></span>
6221                         statement is present or
6222                         an empty list for <span><strong class="command">forwarders</strong></span> is given, then no
6223                         forwarding will be done for the domain, canceling the
6224                         effects of
6225                         any forwarders in the <span><strong class="command">options</strong></span> statement. Thus
6226                         if you want to use this type of zone to change the
6227                         behavior of the
6228                         global <span><strong class="command">forward</strong></span> option
6229                         (that is, "forward first"
6230                         to, then "forward only", or vice versa, but want to
6231                         use the same
6232                         servers as set globally) you need to re-specify the
6233                         global forwarders.
6234                       </p>
6235                     </td>
6236 </tr>
6237 <tr>
6238 <td>
6239                       <p>
6240                         <code class="varname">hint</code>
6241                       </p>
6242                     </td>
6243 <td>
6244                       <p>
6245                         The initial set of root name servers is
6246                         specified using a "hint zone". When the server starts
6247                         up, it uses
6248                         the root hints to find a root name server and get the
6249                         most recent
6250                         list of root name servers. If no hint zone is
6251                         specified for class
6252                         IN, the server uses a compiled-in default set of root
6253                         servers hints.
6254                         Classes other than IN have no built-in defaults hints.
6255                       </p>
6256                     </td>
6257 </tr>
6258 <tr>
6259 <td>
6260                       <p>
6261                         <code class="varname">delegation-only</code>
6262                       </p>
6263                     </td>
6264 <td>
6265                       <p>
6266                         This is used to enforce the delegation-only
6267                         status of infrastructure zones (e.g. COM,
6268                         NET, ORG).  Any answer that is received
6269                         without an explicit or implicit delegation
6270                         in the authority section will be treated
6271                         as NXDOMAIN.  This does not apply to the
6272                         zone apex.  This should not be applied to
6273                         leaf zones.
6274                       </p>
6275                       <p>
6276                         <code class="varname">delegation-only</code> has no
6277                         effect on answers received from forwarders.
6278                       </p>
6279                       <p>
6280                         See caveats in <a href="Bv9ARM.ch06.html#root_delegation_only"><span><strong class="command">root-delegation-only</strong></span></a>.
6281                       </p>
6282                     </td>
6283 </tr>
6284 </tbody>
6285 </table></div>
6286 </div>
6287 <div class="sect3" lang="en">
6288 <div class="titlepage"><div><div><h4 class="title">
6289 <a name="id2590923"></a>Class</h4></div></div></div>
6290 <p>
6291               The zone's name may optionally be followed by a class. If
6292               a class is not specified, class <code class="literal">IN</code> (for <code class="varname">Internet</code>),
6293               is assumed. This is correct for the vast majority of cases.
6294             </p>
6295 <p>
6296               The <code class="literal">hesiod</code> class is
6297               named for an information service from MIT's Project Athena. It
6298               is
6299               used to share information about various systems databases, such
6300               as users, groups, printers and so on. The keyword
6301               <code class="literal">HS</code> is
6302               a synonym for hesiod.
6303             </p>
6304 <p>
6305               Another MIT development is Chaosnet, a LAN protocol created
6306               in the mid-1970s. Zone data for it can be specified with the <code class="literal">CHAOS</code> class.
6307             </p>
6308 </div>
6309 <div class="sect3" lang="en">
6310 <div class="titlepage"><div><div><h4 class="title">
6311 <a name="id2590956"></a>Zone Options</h4></div></div></div>
6312 <div class="variablelist"><dl>
6313 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
6314 <dd><p>
6315                     See the description of
6316                     <span><strong class="command">allow-notify</strong></span> in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
6317                   </p></dd>
6318 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
6319 <dd><p>
6320                     See the description of
6321                     <span><strong class="command">allow-query</strong></span> in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
6322                   </p></dd>
6323 <dt><span class="term"><span><strong class="command">allow-query-on</strong></span></span></dt>
6324 <dd><p>
6325                     See the description of
6326                     <span><strong class="command">allow-query-on</strong></span> in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
6327                   </p></dd>
6328 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
6329 <dd><p>
6330                     See the description of <span><strong class="command">allow-transfer</strong></span>
6331                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
6332                   </p></dd>
6333 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
6334 <dd><p>
6335                     See the description of <span><strong class="command">allow-update</strong></span>
6336                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
6337                   </p></dd>
6338 <dt><span class="term"><span><strong class="command">update-policy</strong></span></span></dt>
6339 <dd><p>
6340                     Specifies a "Simple Secure Update" policy. See
6341                     <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>.
6342                   </p></dd>
6343 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
6344 <dd><p>
6345                     See the description of <span><strong class="command">allow-update-forwarding</strong></span>
6346                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
6347                   </p></dd>
6348 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
6349 <dd><p>
6350                     Only meaningful if <span><strong class="command">notify</strong></span>
6351                     is
6352                     active for this zone. The set of machines that will
6353                     receive a
6354                     <code class="literal">DNS NOTIFY</code> message
6355                     for this zone is made up of all the listed name servers
6356                     (other than
6357                     the primary master) for the zone plus any IP addresses
6358                     specified
6359                     with <span><strong class="command">also-notify</strong></span>. A port
6360                     may be specified
6361                     with each <span><strong class="command">also-notify</strong></span>
6362                     address to send the notify
6363                     messages to a port other than the default of 53.
6364                     <span><strong class="command">also-notify</strong></span> is not
6365                     meaningful for stub zones.
6366                     The default is the empty list.
6367                   </p></dd>
6368 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
6369 <dd><p>
6370                     This option is used to restrict the character set and
6371                     syntax of
6372                     certain domain names in master files and/or DNS responses
6373                     received from the
6374                     network.  The default varies according to zone type.  For <span><strong class="command">master</strong></span> zones the default is <span><strong class="command">fail</strong></span>.  For <span><strong class="command">slave</strong></span>
6375                     zones the default is <span><strong class="command">warn</strong></span>.
6376                     It is not implemented for <span><strong class="command">hint</strong></span> zones.
6377                   </p></dd>
6378 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
6379 <dd><p>
6380                     See the description of
6381                     <span><strong class="command">check-mx</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
6382                   </p></dd>
6383 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
6384 <dd><p>
6385                     See the description of
6386                     <span><strong class="command">check-wildcard</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
6387                   </p></dd>
6388 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
6389 <dd><p>
6390                     See the description of
6391                     <span><strong class="command">check-integrity</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
6392                   </p></dd>
6393 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
6394 <dd><p>
6395                     See the description of
6396                     <span><strong class="command">check-sibling</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
6397                   </p></dd>
6398 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
6399 <dd><p>
6400                     See the description of
6401                     <span><strong class="command">zero-no-soa-ttl</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
6402                   </p></dd>
6403 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
6404 <dd><p>
6405                     See the description of
6406                     <span><strong class="command">update-check-ksk</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
6407                   </p></dd>
6408 <dt><span class="term"><span><strong class="command">dnssec-dnskey-kskonly</strong></span></span></dt>
6409 <dd><p>
6410                     See the description of
6411                     <span><strong class="command">dnssec-dnskey-kskonly</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
6412                   </p></dd>
6413 <dt><span class="term"><span><strong class="command">try-tcp-refresh</strong></span></span></dt>
6414 <dd><p>
6415                     See the description of
6416                     <span><strong class="command">try-tcp-refresh</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
6417                   </p></dd>
6418 <dt><span class="term"><span><strong class="command">database</strong></span></span></dt>
6419 <dd>
6420 <p>
6421                     Specify the type of database to be used for storing the
6422                     zone data.  The string following the <span><strong class="command">database</strong></span> keyword
6423                     is interpreted as a list of whitespace-delimited words.
6424                     The first word
6425                     identifies the database type, and any subsequent words are
6426                     passed
6427                     as arguments to the database to be interpreted in a way
6428                     specific
6429                     to the database type.
6430                   </p>
6431 <p>
6432                     The default is <strong class="userinput"><code>"rbt"</code></strong>, BIND 9's
6433                     native in-memory
6434                     red-black-tree database.  This database does not take
6435                     arguments.
6436                   </p>
6437 <p>
6438                     Other values are possible if additional database drivers
6439                     have been linked into the server.  Some sample drivers are
6440                     included
6441                     with the distribution but none are linked in by default.
6442                   </p>
6443 </dd>
6444 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
6445 <dd><p>
6446                     See the description of
6447                     <span><strong class="command">dialup</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
6448                   </p></dd>
6449 <dt><span class="term"><span><strong class="command">delegation-only</strong></span></span></dt>
6450 <dd>
6451 <p>
6452                     The flag only applies to hint and stub zones.  If set
6453                     to <strong class="userinput"><code>yes</code></strong>, then the zone will also be
6454                     treated as if it is also a delegation-only type zone.
6455                   </p>
6456 <p>
6457                     See caveats in <a href="Bv9ARM.ch06.html#root_delegation_only"><span><strong class="command">root-delegation-only</strong></span></a>.
6458                   </p>
6459 </dd>
6460 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
6461 <dd><p>
6462                     Only meaningful if the zone has a forwarders
6463                     list. The <span><strong class="command">only</strong></span> value causes
6464                     the lookup to fail
6465                     after trying the forwarders and getting no answer, while <span><strong class="command">first</strong></span> would
6466                     allow a normal lookup to be tried.
6467                   </p></dd>
6468 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
6469 <dd><p>
6470                     Used to override the list of global forwarders.
6471                     If it is not specified in a zone of type <span><strong class="command">forward</strong></span>,
6472                     no forwarding is done for the zone and the global options are
6473                     not used.
6474                   </p></dd>
6475 <dt><span class="term"><span><strong class="command">ixfr-base</strong></span></span></dt>
6476 <dd><p>
6477                     Was used in <acronym class="acronym">BIND</acronym> 8 to
6478                     specify the name
6479                     of the transaction log (journal) file for dynamic update
6480                     and IXFR.
6481                     <acronym class="acronym">BIND</acronym> 9 ignores the option
6482                     and constructs the name of the journal
6483                     file by appending "<code class="filename">.jnl</code>"
6484                     to the name of the
6485                     zone file.
6486                   </p></dd>
6487 <dt><span class="term"><span><strong class="command">ixfr-tmp-file</strong></span></span></dt>
6488 <dd><p>
6489                     Was an undocumented option in <acronym class="acronym">BIND</acronym> 8.
6490                     Ignored in <acronym class="acronym">BIND</acronym> 9.
6491                   </p></dd>
6492 <dt><span class="term"><span><strong class="command">journal</strong></span></span></dt>
6493 <dd><p>
6494                     Allow the default journal's filename to be overridden.
6495                     The default is the zone's filename with "<code class="filename">.jnl</code>" appended.
6496                     This is applicable to <span><strong class="command">master</strong></span> and <span><strong class="command">slave</strong></span> zones.
6497                   </p></dd>
6498 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
6499 <dd><p>
6500                     See the description of
6501                     <span><strong class="command">max-journal-size</strong></span> in <a href="Bv9ARM.ch06.html#server_resource_limits" title="Server  Resource Limits">the section called &#8220;Server  Resource Limits&#8221;</a>.
6502                   </p></dd>
6503 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
6504 <dd><p>
6505                     See the description of
6506                     <span><strong class="command">max-transfer-time-in</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
6507                   </p></dd>
6508 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
6509 <dd><p>
6510                     See the description of
6511                     <span><strong class="command">max-transfer-idle-in</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
6512                   </p></dd>
6513 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
6514 <dd><p>
6515                     See the description of
6516                     <span><strong class="command">max-transfer-time-out</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
6517                   </p></dd>
6518 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
6519 <dd><p>
6520                     See the description of
6521                     <span><strong class="command">max-transfer-idle-out</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
6522                   </p></dd>
6523 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
6524 <dd><p>
6525                     See the description of
6526                     <span><strong class="command">notify</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
6527                   </p></dd>
6528 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
6529 <dd><p>
6530                     See the description of
6531                     <span><strong class="command">notify-delay</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
6532                   </p></dd>
6533 <dt><span class="term"><span><strong class="command">notify-to-soa</strong></span></span></dt>
6534 <dd><p>
6535                     See the description of
6536                     <span><strong class="command">notify-to-soa</strong></span> in
6537                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
6538                   </p></dd>
6539 <dt><span class="term"><span><strong class="command">pubkey</strong></span></span></dt>
6540 <dd><p>
6541                     In <acronym class="acronym">BIND</acronym> 8, this option was
6542                     intended for specifying
6543                     a public zone key for verification of signatures in DNSSEC
6544                     signed
6545                     zones when they are loaded from disk. <acronym class="acronym">BIND</acronym> 9 does not verify signatures
6546                     on load and ignores the option.
6547                   </p></dd>
6548 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
6549 <dd><p>
6550                     If <strong class="userinput"><code>yes</code></strong>, the server will keep
6551                     statistical
6552                     information for this zone, which can be dumped to the
6553                     <span><strong class="command">statistics-file</strong></span> defined in
6554                     the server options.
6555                   </p></dd>
6556 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
6557 <dd><p>
6558                     See the description of
6559                     <span><strong class="command">sig-validity-interval</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
6560                   </p></dd>
6561 <dt><span class="term"><span><strong class="command">sig-signing-nodes</strong></span></span></dt>
6562 <dd><p>
6563                     See the description of
6564                     <span><strong class="command">sig-signing-nodes</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
6565                   </p></dd>
6566 <dt><span class="term"><span><strong class="command">sig-signing-signatures</strong></span></span></dt>
6567 <dd><p>
6568                     See the description of
6569                     <span><strong class="command">sig-signing-signatures</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
6570                   </p></dd>
6571 <dt><span class="term"><span><strong class="command">sig-signing-type</strong></span></span></dt>
6572 <dd><p>
6573                     See the description of
6574                     <span><strong class="command">sig-signing-type</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
6575                   </p></dd>
6576 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
6577 <dd><p>
6578                     See the description of
6579                     <span><strong class="command">transfer-source</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
6580                   </p></dd>
6581 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
6582 <dd><p>
6583                     See the description of
6584                     <span><strong class="command">transfer-source-v6</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
6585                   </p></dd>
6586 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
6587 <dd><p>
6588                     See the description of
6589                     <span><strong class="command">alt-transfer-source</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
6590                   </p></dd>
6591 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
6592 <dd><p>
6593                     See the description of
6594                     <span><strong class="command">alt-transfer-source-v6</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
6595                   </p></dd>
6596 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
6597 <dd><p>
6598                     See the description of
6599                     <span><strong class="command">use-alt-transfer-source</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
6600                   </p></dd>
6601 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
6602 <dd><p>
6603                     See the description of
6604                     <span><strong class="command">notify-source</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
6605                   </p></dd>
6606 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
6607 <dd><p>
6608                     See the description of
6609                     <span><strong class="command">notify-source-v6</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
6610                   </p></dd>
6611 <dt>
6612 <span class="term"><span><strong class="command">min-refresh-time</strong></span>, </span><span class="term"><span><strong class="command">max-refresh-time</strong></span>, </span><span class="term"><span><strong class="command">min-retry-time</strong></span>, </span><span class="term"><span><strong class="command">max-retry-time</strong></span></span>
6613 </dt>
6614 <dd><p>
6615                     See the description in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
6616                   </p></dd>
6617 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
6618 <dd><p>
6619                     See the description of
6620                     <span><strong class="command">ixfr-from-differences</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
6621                     (Note that the <span><strong class="command">ixfr-from-differences</strong></span>
6622                     <strong class="userinput"><code>master</code></strong> and
6623                     <strong class="userinput"><code>slave</code></strong> choices are not
6624                     available at the zone level.)
6625                   </p></dd>
6626 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
6627 <dd><p>
6628                     See the description of
6629                     <span><strong class="command">key-directory</strong></span> in <a href="Bv9ARM.ch06.html#options" title="options Statement Definition and
6630           Usage">the section called &#8220;<span><strong class="command">options</strong></span> Statement Definition and
6631           Usage&#8221;</a>.
6632                   </p></dd>
6633 <dt><span class="term"><span><strong class="command">auto-dnssec</strong></span></span></dt>
6634 <dd>
6635 <p>
6636                     Zones configured for dynamic DNS may also use this
6637                     option to allow varying levels of autonatic DNSSEC key
6638                     management. There are four possible settings:
6639                   </p>
6640 <p>
6641                     <span><strong class="command">auto-dnssec allow;</strong></span> permits
6642                     keys to be updated and the zone re-signed whenever the
6643                     user issues the command <span><strong class="command">rndc sign
6644                     <em class="replaceable"><code>zonename</code></em></strong></span>.
6645                   </p>
6646 <p>
6647                     <span><strong class="command">auto-dnssec maintain;</strong></span> includes the
6648                     above, but also automatically adjusts the zone's DNSSEC
6649                     keys on schedule, according to the keys' timing metadata
6650                     (see <a href="man.dnssec-keygen.html" title="dnssec-keygen"><span class="refentrytitle"><span class="application">dnssec-keygen</span></span>(8)</a> and
6651                     <a href="man.dnssec-settime.html" title="dnssec-settime"><span class="refentrytitle"><span class="application">dnssec-settime</span></span>(8)</a>).
6652                   </p>
6653 <p>
6654                     <span><strong class="command">auto-dnssec create;</strong></span> includes the
6655                     above, but also allows <span><strong class="command">named</strong></span>
6656                     to create new keys in the key repository when needed.
6657                     (NOTE: This option is not yet implemented; the syntax is
6658                     being reserved for future use.)
6659                   </p>
6660 <p>
6661                     The default setting is <span><strong class="command">auto-dnssec off</strong></span>.
6662                   </p>
6663 </dd>
6664 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
6665 <dd><p>
6666                     See the description of <span><strong class="command">multi-master</strong></span> in
6667                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
6668                   </p></dd>
6669 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
6670 <dd><p>
6671                     See the description of <span><strong class="command">masterfile-format</strong></span>
6672                     in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
6673                   </p></dd>
6674 <dt><span class="term"><span><strong class="command">dnssec-secure-to-insecure</strong></span></span></dt>
6675 <dd><p>
6676                     See the description of
6677                     <span><strong class="command">dnssec-secure-to-insecure</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
6678                   </p></dd>
6679 </dl></div>
6680 </div>
6681 <div class="sect3" lang="en">
6682 <div class="titlepage"><div><div><h4 class="title">
6683 <a name="dynamic_update_policies"></a>Dynamic Update Policies</h4></div></div></div>
6684 <p><acronym class="acronym">BIND</acronym> 9 supports two alternative
6685               methods of granting clients the right to perform
6686               dynamic updates to a zone, configured by the
6687               <span><strong class="command">allow-update</strong></span> and
6688               <span><strong class="command">update-policy</strong></span> option, respectively.
6689             </p>
6690 <p>
6691               The <span><strong class="command">allow-update</strong></span> clause works the
6692               same way as in previous versions of <acronym class="acronym">BIND</acronym>.
6693               It grants given clients the permission to update any
6694               record of any name in the zone.
6695             </p>
6696 <p>
6697               The <span><strong class="command">update-policy</strong></span> clause
6698               allows more fine-grained control over what updates are
6699               allowed.  A set of rules is specified, where each rule
6700               either grants or denies permissions for one or more
6701               names to be updated by one or more identities.  If
6702               the dynamic update request message is signed (that is,
6703               it includes either a TSIG or SIG(0) record), the
6704               identity of the signer can be determined.
6705             </p>
6706 <p>
6707               Rules are specified in the <span><strong class="command">update-policy</strong></span>
6708               zone option, and are only meaningful for master zones.
6709               When the <span><strong class="command">update-policy</strong></span> statement
6710               is present, it is a configuration error for the
6711               <span><strong class="command">allow-update</strong></span> statement to be
6712               present.  The <span><strong class="command">update-policy</strong></span> statement
6713               only examines the signer of a message; the source
6714               address is not relevant.
6715             </p>
6716 <p>
6717               There is a pre-defined <span><strong class="command">update-policy</strong></span>
6718               rule which can be switched on with the command
6719               <span><strong class="command">update-policy local;</strong></span>.
6720               Switching on this rule in a zone causes
6721               <span><strong class="command">named</strong></span> to generate a TSIG session
6722               key and place it in a file, and to allow that key
6723               to update the zone.  (By default, the file is
6724               <code class="filename">/var/run/named/session.key</code>, the key
6725               name is "local-ddns" and the key algorithm is HMAC-SHA256,
6726               but these values are configurable with the
6727               <span><strong class="command">session-keyfile</strong></span>,
6728               <span><strong class="command">session-keyname</strong></span> and
6729               <span><strong class="command">session-keyalg</strong></span> options, respectively).
6730             </p>
6731 <p>
6732               A client running on the local system, and with appropriate
6733               permissions, may read that file and use the key to sign update
6734               requests.  The zone's update policy will be set to allow that
6735               key to change any record within the zone.  Assuming the
6736               key name is "local-ddns", this policy is equivalent to:
6737             </p>
6738 <pre class="programlisting">update-policy { grant local-ddns zonesub any; };
6739             </pre>
6740 <p>
6741               The command <span><strong class="command">nsupdate -l</strong></span> sends update
6742               requests to localhost, and signs them using the session key.
6743             </p>
6744 <p>
6745               Other rule definitions look like this:
6746             </p>
6747 <pre class="programlisting">
6748 ( <span><strong class="command">grant</strong></span> | <span><strong class="command">deny</strong></span> ) <em class="replaceable"><code>identity</code></em> <em class="replaceable"><code>nametype</code></em> [<span class="optional"> <em class="replaceable"><code>name</code></em> </span>] [<span class="optional"> <em class="replaceable"><code>types</code></em> </span>]
6749 </pre>
6750 <p>
6751               Each rule grants or denies privileges.  Once a message has
6752               successfully matched a rule, the operation is immediately
6753               granted or denied and no further rules are examined.  A rule
6754               is matched when the signer matches the identity field, the
6755               name matches the name field in accordance with the nametype
6756               field, and the type matches the types specified in the type
6757               field.
6758             </p>
6759 <p>
6760               No signer is required for <em class="replaceable"><code>tcp-self</code></em>
6761               or <em class="replaceable"><code>6to4-self</code></em> however the standard
6762               reverse mapping / prefix conversion must match the identity
6763               field.
6764             </p>
6765 <p>
6766               The identity field specifies a name or a wildcard
6767               name.  Normally, this is the name of the TSIG or
6768               SIG(0) key used to sign the update request.  When a
6769               TKEY exchange has been used to create a shared secret,
6770               the identity of the shared secret is the same as the
6771               identity of the key used to authenticate the TKEY
6772               exchange.  TKEY is also the negotiation method used
6773               by GSS-TSIG, which establishes an identity that is
6774               the Kerberos principal of the client, such as
6775               <strong class="userinput"><code>"user@host.domain"</code></strong>.  When the
6776               <em class="replaceable"><code>identity</code></em> field specifies
6777               a wildcard name, it is subject to DNS wildcard
6778               expansion, so the rule will apply to multiple identities.
6779               The <em class="replaceable"><code>identity</code></em> field must
6780               contain a fully-qualified domain name.
6781             </p>
6782 <p>
6783               The <em class="replaceable"><code>nametype</code></em> field has 13
6784               values:
6785               <code class="varname">name</code>, <code class="varname">subdomain</code>,
6786               <code class="varname">wildcard</code>, <code class="varname">self</code>,
6787               <code class="varname">selfsub</code>, <code class="varname">selfwild</code>,
6788               <code class="varname">krb5-self</code>, <code class="varname">ms-self</code>,
6789               <code class="varname">krb5-subdomain</code>,
6790               <code class="varname">ms-subdomain</code>,
6791               <code class="varname">tcp-self</code>, <code class="varname">6to4-self</code>,
6792               and <code class="varname">zonesub</code>.
6793             </p>
6794 <div class="informaltable"><table border="1">
6795 <colgroup>
6796 <col>
6797 <col>
6798 </colgroup>
6799 <tbody>
6800 <tr>
6801 <td>
6802                       <p>
6803                         <code class="varname">name</code>
6804                       </p>
6805                     </td>
6806 <td>
6807                       <p>
6808                         Exact-match semantics.  This rule matches
6809                         when the name being updated is identical
6810                         to the contents of the
6811                         <em class="replaceable"><code>name</code></em> field.
6812                       </p>
6813                     </td>
6814 </tr>
6815 <tr>
6816 <td>
6817                       <p>
6818                         <code class="varname">subdomain</code>
6819                       </p>
6820                     </td>
6821 <td>
6822                       <p>
6823                         This rule matches when the name being updated
6824                         is a subdomain of, or identical to, the
6825                         contents of the <em class="replaceable"><code>name</code></em>
6826                         field.
6827                       </p>
6828                     </td>
6829 </tr>
6830 <tr>
6831 <td>
6832                       <p>
6833                         <code class="varname">zonesub</code>
6834                       </p>
6835                     </td>
6836 <td>
6837                       <p>
6838                         This rule is similar to subdomain, except that
6839                         it matches when the name being updated is a
6840                         subdomain of the zone in which the
6841                         <span><strong class="command">update-policy</strong></span> statement
6842                         appears.  This obviates the need to type the zone
6843                         name twice, and enables the use of a standard
6844                         <span><strong class="command">update-policy</strong></span> statement in
6845                         multiple zones without modification.
6846                       </p>
6847                       <p>
6848                         When this rule is used, the
6849                         <em class="replaceable"><code>name</code></em> field is omitted.
6850                       </p>
6851                     </td>
6852 </tr>
6853 <tr>
6854 <td>
6855                       <p>
6856                         <code class="varname">wildcard</code>
6857                       </p>
6858                     </td>
6859 <td>
6860                       <p>
6861                         The <em class="replaceable"><code>name</code></em> field
6862                         is subject to DNS wildcard expansion, and
6863                         this rule matches when the name being updated
6864                         name is a valid expansion of the wildcard.
6865                       </p>
6866                     </td>
6867 </tr>
6868 <tr>
6869 <td>
6870                       <p>
6871                         <code class="varname">self</code>
6872                       </p>
6873                     </td>
6874 <td>
6875                       <p>
6876                         This rule matches when the name being updated
6877                         matches the contents of the
6878                         <em class="replaceable"><code>identity</code></em> field.
6879                         The <em class="replaceable"><code>name</code></em> field
6880                         is ignored, but should be the same as the
6881                         <em class="replaceable"><code>identity</code></em> field.
6882                         The <code class="varname">self</code> nametype is
6883                         most useful when allowing using one key per
6884                         name to update, where the key has the same
6885                         name as the name to be updated.  The
6886                         <em class="replaceable"><code>identity</code></em> would
6887                         be specified as <code class="constant">*</code> (an asterisk) in
6888                         this case.
6889                       </p>
6890                     </td>
6891 </tr>
6892 <tr>
6893 <td>
6894                       <p>
6895                         <code class="varname">selfsub</code>
6896                       </p>
6897                     </td>
6898 <td>
6899                       <p>
6900                         This rule is similar to <code class="varname">self</code>
6901                         except that subdomains of <code class="varname">self</code>
6902                         can also be updated.
6903                       </p>
6904                     </td>
6905 </tr>
6906 <tr>
6907 <td>
6908                       <p>
6909                         <code class="varname">selfwild</code>
6910                       </p>
6911                     </td>
6912 <td>
6913                       <p>
6914                         This rule is similar to <code class="varname">self</code>
6915                         except that only subdomains of
6916                         <code class="varname">self</code> can be updated.
6917                       </p>
6918                     </td>
6919 </tr>
6920 <tr>
6921 <td>
6922                       <p>
6923                         <code class="varname">tcp-self</code>
6924                       </p>
6925                     </td>
6926 <td>
6927                       <p>
6928                         Allow updates that have been sent via TCP and
6929                         for which the standard mapping from the initiating
6930                         IP address into the IN-ADDR.ARPA and IP6.ARPA
6931                         namespaces match the name to be updated.
6932                       </p>
6933                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
6934 <h3 class="title">Note</h3>
6935                         It is theoretically possible to spoof these TCP
6936                         sessions.
6937                       </div>
6938                     </td>
6939 </tr>
6940 <tr>
6941 <td>
6942                       <p>
6943                         <code class="varname">6to4-self</code>
6944                       </p>
6945                     </td>
6946 <td>
6947                       <p>
6948                         Allow the 6to4 prefix to be update by any TCP
6949                         connection from the 6to4 network or from the
6950                         corresponding IPv4 address.  This is intended
6951                         to allow NS or DNAME RRsets to be added to the
6952                         reverse tree.
6953                       </p>
6954                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
6955 <h3 class="title">Note</h3>
6956                         It is theoretically possible to spoof these TCP
6957                         sessions.
6958                       </div>
6959                     </td>
6960 </tr>
6961 </tbody>
6962 </table></div>
6963 <p>
6964               In all cases, the <em class="replaceable"><code>name</code></em>
6965               field must
6966               specify a fully-qualified domain name.
6967             </p>
6968 <p>
6969               If no types are explicitly specified, this rule matches
6970               all types except RRSIG, NS, SOA, NSEC and NSEC3. Types
6971               may be specified by name, including "ANY" (ANY matches
6972               all types except NSEC and NSEC3, which can never be
6973               updated).  Note that when an attempt is made to delete
6974               all records associated with a name, the rules are
6975               checked for each existing record type.
6976             </p>
6977 </div>
6978 </div>
6979 </div>
6980 <div class="sect1" lang="en">
6981 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
6982 <a name="id2593224"></a>Zone File</h2></div></div></div>
6983 <div class="sect2" lang="en">
6984 <div class="titlepage"><div><div><h3 class="title">
6985 <a name="types_of_resource_records_and_when_to_use_them"></a>Types of Resource Records and When to Use Them</h3></div></div></div>
6986 <p>
6987             This section, largely borrowed from RFC 1034, describes the
6988             concept of a Resource Record (RR) and explains when each is used.
6989             Since the publication of RFC 1034, several new RRs have been
6990             identified
6991             and implemented in the DNS. These are also included.
6992           </p>
6993 <div class="sect3" lang="en">
6994 <div class="titlepage"><div><div><h4 class="title">
6995 <a name="id2593242"></a>Resource Records</h4></div></div></div>
6996 <p>
6997               A domain name identifies a node.  Each node has a set of
6998               resource information, which may be empty.  The set of resource
6999               information associated with a particular name is composed of
7000               separate RRs. The order of RRs in a set is not significant and
7001               need not be preserved by name servers, resolvers, or other
7002               parts of the DNS. However, sorting of multiple RRs is
7003               permitted for optimization purposes, for example, to specify
7004               that a particular nearby server be tried first. See <a href="Bv9ARM.ch06.html#the_sortlist_statement" title="The sortlist Statement">the section called &#8220;The <span><strong class="command">sortlist</strong></span> Statement&#8221;</a> and <a href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">the section called &#8220;RRset Ordering&#8221;</a>.
7005             </p>
7006 <p>
7007               The components of a Resource Record are:
7008             </p>
7009 <div class="informaltable"><table border="1">
7010 <colgroup>
7011 <col>
7012 <col>
7013 </colgroup>
7014 <tbody>
7015 <tr>
7016 <td>
7017                       <p>
7018                         owner name
7019                       </p>
7020                     </td>
7021 <td>
7022                       <p>
7023                         The domain name where the RR is found.
7024                       </p>
7025                     </td>
7026 </tr>
7027 <tr>
7028 <td>
7029                       <p>
7030                         type
7031                       </p>
7032                     </td>
7033 <td>
7034                       <p>
7035                         An encoded 16-bit value that specifies
7036                         the type of the resource record.
7037                       </p>
7038                     </td>
7039 </tr>
7040 <tr>
7041 <td>
7042                       <p>
7043                         TTL
7044                       </p>
7045                     </td>
7046 <td>
7047                       <p>
7048                         The time-to-live of the RR. This field
7049                         is a 32-bit integer in units of seconds, and is
7050                         primarily used by
7051                         resolvers when they cache RRs. The TTL describes how
7052                         long a RR can
7053                         be cached before it should be discarded.
7054                       </p>
7055                     </td>
7056 </tr>
7057 <tr>
7058 <td>
7059                       <p>
7060                         class
7061                       </p>
7062                     </td>
7063 <td>
7064                       <p>
7065                         An encoded 16-bit value that identifies
7066                         a protocol family or instance of a protocol.
7067                       </p>
7068                     </td>
7069 </tr>
7070 <tr>
7071 <td>
7072                       <p>
7073                         RDATA
7074                       </p>
7075                     </td>
7076 <td>
7077                       <p>
7078                         The resource data.  The format of the
7079                         data is type (and sometimes class) specific.
7080                       </p>
7081                     </td>
7082 </tr>
7083 </tbody>
7084 </table></div>
7085 <p>
7086               The following are <span class="emphasis"><em>types</em></span> of valid RRs:
7087             </p>
7088 <div class="informaltable"><table border="1">
7089 <colgroup>
7090 <col>
7091 <col>
7092 </colgroup>
7093 <tbody>
7094 <tr>
7095 <td>
7096                       <p>
7097                         A
7098                       </p>
7099                     </td>
7100 <td>
7101                       <p>
7102                         A host address.  In the IN class, this is a
7103                         32-bit IP address.  Described in RFC 1035.
7104                       </p>
7105                     </td>
7106 </tr>
7107 <tr>
7108 <td>
7109                       <p>
7110                         AAAA
7111                       </p>
7112                     </td>
7113 <td>
7114                       <p>
7115                         IPv6 address.  Described in RFC 1886.
7116                       </p>
7117                     </td>
7118 </tr>
7119 <tr>
7120 <td>
7121                       <p>
7122                         A6
7123                       </p>
7124                     </td>
7125 <td>
7126                       <p>
7127                         IPv6 address.  This can be a partial
7128                         address (a suffix) and an indirection to the name
7129                         where the rest of the
7130                         address (the prefix) can be found.  Experimental.
7131                         Described in RFC 2874.
7132                       </p>
7133                     </td>
7134 </tr>
7135 <tr>
7136 <td>
7137                       <p>
7138                         AFSDB
7139                       </p>
7140                     </td>
7141 <td>
7142                       <p>
7143                         Location of AFS database servers.
7144                         Experimental.  Described in RFC 1183.
7145                       </p>
7146                     </td>
7147 </tr>
7148 <tr>
7149 <td>
7150                       <p>
7151                         APL
7152                       </p>
7153                     </td>
7154 <td>
7155                       <p>
7156                         Address prefix list.  Experimental.
7157                         Described in RFC 3123.
7158                       </p>
7159                     </td>
7160 </tr>
7161 <tr>
7162 <td>
7163                       <p>
7164                         CERT
7165                       </p>
7166                     </td>
7167 <td>
7168                       <p>
7169                         Holds a digital certificate.
7170                         Described in RFC 2538.
7171                       </p>
7172                     </td>
7173 </tr>
7174 <tr>
7175 <td>
7176                       <p>
7177                         CNAME
7178                       </p>
7179                     </td>
7180 <td>
7181                       <p>
7182                         Identifies the canonical name of an alias.
7183                         Described in RFC 1035.
7184                       </p>
7185                     </td>
7186 </tr>
7187 <tr>
7188 <td>
7189                       <p>
7190                         DHCID
7191                       </p>
7192                     </td>
7193 <td>
7194                       <p>
7195                         Is used for identifying which DHCP client is
7196                         associated with this name.  Described in RFC 4701.
7197                       </p>
7198                     </td>
7199 </tr>
7200 <tr>
7201 <td>
7202                       <p>
7203                         DNAME
7204                       </p>
7205                     </td>
7206 <td>
7207                       <p>
7208                         Replaces the domain name specified with
7209                         another name to be looked up, effectively aliasing an
7210                         entire
7211                         subtree of the domain name space rather than a single
7212                         record
7213                         as in the case of the CNAME RR.
7214                         Described in RFC 2672.
7215                       </p>
7216                     </td>
7217 </tr>
7218 <tr>
7219 <td>
7220                       <p>
7221                         DNSKEY
7222                       </p>
7223                     </td>
7224 <td>
7225                       <p>
7226                         Stores a public key associated with a signed
7227                         DNS zone.  Described in RFC 4034.
7228                       </p>
7229                     </td>
7230 </tr>
7231 <tr>
7232 <td>
7233                       <p>
7234                         DS
7235                       </p>
7236                     </td>
7237 <td>
7238                       <p>
7239                         Stores the hash of a public key associated with a
7240                         signed DNS zone.  Described in RFC 4034.
7241                       </p>
7242                     </td>
7243 </tr>
7244 <tr>
7245 <td>
7246                       <p>
7247                         GPOS
7248                       </p>
7249                     </td>
7250 <td>
7251                       <p>
7252                         Specifies the global position.  Superseded by LOC.
7253                       </p>
7254                     </td>
7255 </tr>
7256 <tr>
7257 <td>
7258                       <p>
7259                         HINFO
7260                       </p>
7261                     </td>
7262 <td>
7263                       <p>
7264                         Identifies the CPU and OS used by a host.
7265                         Described in RFC 1035.
7266                       </p>
7267                     </td>
7268 </tr>
7269 <tr>
7270 <td>
7271                       <p>
7272                         IPSECKEY
7273                       </p>
7274                     </td>
7275 <td>
7276                       <p>
7277                         Provides a method for storing IPsec keying material in
7278                         DNS.  Described in RFC 4025.
7279                       </p>
7280                     </td>
7281 </tr>
7282 <tr>
7283 <td>
7284                       <p>
7285                         ISDN
7286                       </p>
7287                     </td>
7288 <td>
7289                       <p>
7290                         Representation of ISDN addresses.
7291                         Experimental.  Described in RFC 1183.
7292                       </p>
7293                     </td>
7294 </tr>
7295 <tr>
7296 <td>
7297                       <p>
7298                         KEY
7299                       </p>
7300                     </td>
7301 <td>
7302                       <p>
7303                         Stores a public key associated with a
7304                         DNS name.  Used in original DNSSEC; replaced
7305                         by DNSKEY in DNSSECbis, but still used with
7306                         SIG(0).  Described in RFCs 2535 and 2931.
7307                       </p>
7308                     </td>
7309 </tr>
7310 <tr>
7311 <td>
7312                       <p>
7313                         KX
7314                       </p>
7315                     </td>
7316 <td>
7317                       <p>
7318                         Identifies a key exchanger for this
7319                         DNS name.  Described in RFC 2230.
7320                       </p>
7321                     </td>
7322 </tr>
7323 <tr>
7324 <td>
7325                       <p>
7326                         LOC
7327                       </p>
7328                     </td>
7329 <td>
7330                       <p>
7331                         For storing GPS info.  Described in RFC 1876.
7332                         Experimental.
7333                       </p>
7334                     </td>
7335 </tr>
7336 <tr>
7337 <td>
7338                       <p>
7339                         MX
7340                       </p>
7341                     </td>
7342 <td>
7343                       <p>
7344                         Identifies a mail exchange for the domain with
7345                         a 16-bit preference value (lower is better)
7346                         followed by the host name of the mail exchange.
7347                         Described in RFC 974, RFC 1035.
7348                       </p>
7349                     </td>
7350 </tr>
7351 <tr>
7352 <td>
7353                       <p>
7354                         NAPTR
7355                       </p>
7356                     </td>
7357 <td>
7358                       <p>
7359                         Name authority pointer.  Described in RFC 2915.
7360                       </p>
7361                     </td>
7362 </tr>
7363 <tr>
7364 <td>
7365                       <p>
7366                         NSAP
7367                       </p>
7368                     </td>
7369 <td>
7370                       <p>
7371                         A network service access point.
7372                         Described in RFC 1706.
7373                       </p>
7374                     </td>
7375 </tr>
7376 <tr>
7377 <td>
7378                       <p>
7379                         NS
7380                       </p>
7381                     </td>
7382 <td>
7383                       <p>
7384                         The authoritative name server for the
7385                         domain.  Described in RFC 1035.
7386                       </p>
7387                     </td>
7388 </tr>
7389 <tr>
7390 <td>
7391                       <p>
7392                         NSEC
7393                       </p>
7394                     </td>
7395 <td>
7396                       <p>
7397                         Used in DNSSECbis to securely indicate that
7398                         RRs with an owner name in a certain name interval do
7399                         not exist in
7400                         a zone and indicate what RR types are present for an
7401                         existing name.
7402                         Described in RFC 4034.
7403                       </p>
7404                     </td>
7405 </tr>
7406 <tr>
7407 <td>
7408                       <p>
7409                         NSEC3
7410                       </p>
7411                     </td>
7412 <td>
7413                       <p>
7414                         Used in DNSSECbis to securely indicate that
7415                         RRs with an owner name in a certain name
7416                         interval do not exist in a zone and indicate
7417                         what RR types are present for an existing
7418                         name.  NSEC3 differs from NSEC in that it
7419                         prevents zone enumeration but is more
7420                         computationally expensive on both the server
7421                         and the client than NSEC.  Described in RFC
7422                         5155.
7423                       </p>
7424                     </td>
7425 </tr>
7426 <tr>
7427 <td>
7428                       <p>
7429                         NSEC3PARAM
7430                       </p>
7431                     </td>
7432 <td>
7433                       <p>
7434                         Used in DNSSECbis to tell the authoritative
7435                         server which NSEC3 chains are available to use.
7436                         Described in RFC 5155.
7437                       </p>
7438                     </td>
7439 </tr>
7440 <tr>
7441 <td>
7442                       <p>
7443                         NXT
7444                       </p>
7445                     </td>
7446 <td>
7447                       <p>
7448                         Used in DNSSEC to securely indicate that
7449                         RRs with an owner name in a certain name interval do
7450                         not exist in
7451                         a zone and indicate what RR types are present for an
7452                         existing name.
7453                         Used in original DNSSEC; replaced by NSEC in
7454                         DNSSECbis.
7455                         Described in RFC 2535.
7456                       </p>
7457                     </td>
7458 </tr>
7459 <tr>
7460 <td>
7461                       <p>
7462                         PTR
7463                       </p>
7464                     </td>
7465 <td>
7466                       <p>
7467                         A pointer to another part of the domain
7468                         name space.  Described in RFC 1035.
7469                       </p>
7470                     </td>
7471 </tr>
7472 <tr>
7473 <td>
7474                       <p>
7475                         PX
7476                       </p>
7477                     </td>
7478 <td>
7479                       <p>
7480                         Provides mappings between RFC 822 and X.400
7481                         addresses.  Described in RFC 2163.
7482                       </p>
7483                     </td>
7484 </tr>
7485 <tr>
7486 <td>
7487                       <p>
7488                         RP
7489                       </p>
7490                     </td>
7491 <td>
7492                       <p>
7493                         Information on persons responsible
7494                         for the domain.  Experimental.  Described in RFC 1183.
7495                       </p>
7496                     </td>
7497 </tr>
7498 <tr>
7499 <td>
7500                       <p>
7501                         RRSIG
7502                       </p>
7503                     </td>
7504 <td>
7505                       <p>
7506                         Contains DNSSECbis signature data.  Described
7507                         in RFC 4034.
7508                       </p>
7509                     </td>
7510 </tr>
7511 <tr>
7512 <td>
7513                       <p>
7514                         RT
7515                       </p>
7516                     </td>
7517 <td>
7518                       <p>
7519                         Route-through binding for hosts that
7520                         do not have their own direct wide area network
7521                         addresses.
7522                         Experimental.  Described in RFC 1183.
7523                       </p>
7524                     </td>
7525 </tr>
7526 <tr>
7527 <td>
7528                       <p>
7529                         SIG
7530                       </p>
7531                     </td>
7532 <td>
7533                       <p>
7534                         Contains DNSSEC signature data.  Used in
7535                         original DNSSEC; replaced by RRSIG in
7536                         DNSSECbis, but still used for SIG(0).
7537                         Described in RFCs 2535 and 2931.
7538                       </p>
7539                     </td>
7540 </tr>
7541 <tr>
7542 <td>
7543                       <p>
7544                         SOA
7545                       </p>
7546                     </td>
7547 <td>
7548                       <p>
7549                         Identifies the start of a zone of authority.
7550                         Described in RFC 1035.
7551                       </p>
7552                     </td>
7553 </tr>
7554 <tr>
7555 <td>
7556                       <p>
7557                         SPF
7558                       </p>
7559                     </td>
7560 <td>
7561                       <p>
7562                         Contains the Sender Policy Framework information
7563                         for a given email domain.  Described in RFC 4408.
7564                       </p>
7565                     </td>
7566 </tr>
7567 <tr>
7568 <td>
7569                       <p>
7570                         SRV
7571                       </p>
7572                     </td>
7573 <td>
7574                       <p>
7575                         Information about well known network
7576                         services (replaces WKS).  Described in RFC 2782.
7577                       </p>
7578                     </td>
7579 </tr>
7580 <tr>
7581 <td>
7582                       <p>
7583                         SSHFP
7584                       </p>
7585                     </td>
7586 <td>
7587                       <p>
7588                         Provides a way to securely publish a secure shell key's
7589                         fingerprint.  Described in RFC 4255.
7590                       </p>
7591                     </td>
7592 </tr>
7593 <tr>
7594 <td>
7595                       <p>
7596                         TXT
7597                       </p>
7598                     </td>
7599 <td>
7600                       <p>
7601                         Text records.  Described in RFC 1035.
7602                       </p>
7603                     </td>
7604 </tr>
7605 <tr>
7606 <td>
7607                       <p>
7608                         WKS
7609                       </p>
7610                     </td>
7611 <td>
7612                       <p>
7613                         Information about which well known
7614                         network services, such as SMTP, that a domain
7615                         supports. Historical.
7616                       </p>
7617                     </td>
7618 </tr>
7619 <tr>
7620 <td>
7621                       <p>
7622                         X25
7623                       </p>
7624                     </td>
7625 <td>
7626                       <p>
7627                         Representation of X.25 network addresses.
7628                         Experimental.  Described in RFC 1183.
7629                       </p>
7630                     </td>
7631 </tr>
7632 </tbody>
7633 </table></div>
7634 <p>
7635               The following <span class="emphasis"><em>classes</em></span> of resource records
7636               are currently valid in the DNS:
7637             </p>
7638 <div class="informaltable"><table border="1">
7639 <colgroup>
7640 <col>
7641 <col>
7642 </colgroup>
7643 <tbody>
7644 <tr>
7645 <td>
7646                       <p>
7647                         IN
7648                       </p>
7649                     </td>
7650 <td>
7651                       <p>
7652                         The Internet.
7653                       </p>
7654                     </td>
7655 </tr>
7656 <tr>
7657 <td>
7658                       <p>
7659                         CH
7660                       </p>
7661                     </td>
7662 <td>
7663                       <p>
7664                         Chaosnet, a LAN protocol created at MIT in the
7665                         mid-1970s.
7666                         Rarely used for its historical purpose, but reused for
7667                         BIND's
7668                         built-in server information zones, e.g.,
7669                         <code class="literal">version.bind</code>.
7670                       </p>
7671                     </td>
7672 </tr>
7673 <tr>
7674 <td>
7675                       <p>
7676                         HS
7677                       </p>
7678                     </td>
7679 <td>
7680                       <p>
7681                         Hesiod, an information service
7682                         developed by MIT's Project Athena. It is used to share
7683                         information
7684                         about various systems databases, such as users,
7685                         groups, printers
7686                         and so on.
7687                       </p>
7688                     </td>
7689 </tr>
7690 </tbody>
7691 </table></div>
7692 <p>
7693               The owner name is often implicit, rather than forming an
7694               integral
7695               part of the RR.  For example, many name servers internally form
7696               tree
7697               or hash structures for the name space, and chain RRs off nodes.
7698               The remaining RR parts are the fixed header (type, class, TTL)
7699               which is consistent for all RRs, and a variable part (RDATA)
7700               that
7701               fits the needs of the resource being described.
7702             </p>
7703 <p>
7704               The meaning of the TTL field is a time limit on how long an
7705               RR can be kept in a cache.  This limit does not apply to
7706               authoritative
7707               data in zones; it is also timed out, but by the refreshing
7708               policies
7709               for the zone.  The TTL is assigned by the administrator for the
7710               zone where the data originates.  While short TTLs can be used to
7711               minimize caching, and a zero TTL prohibits caching, the
7712               realities
7713               of Internet performance suggest that these times should be on
7714               the
7715               order of days for the typical host.  If a change can be
7716               anticipated,
7717               the TTL can be reduced prior to the change to minimize
7718               inconsistency
7719               during the change, and then increased back to its former value
7720               following
7721               the change.
7722             </p>
7723 <p>
7724               The data in the RDATA section of RRs is carried as a combination
7725               of binary strings and domain names.  The domain names are
7726               frequently
7727               used as "pointers" to other data in the DNS.
7728             </p>
7729 </div>
7730 <div class="sect3" lang="en">
7731 <div class="titlepage"><div><div><h4 class="title">
7732 <a name="id2594934"></a>Textual expression of RRs</h4></div></div></div>
7733 <p>
7734               RRs are represented in binary form in the packets of the DNS
7735               protocol, and are usually represented in highly encoded form
7736               when
7737               stored in a name server or resolver.  In the examples provided
7738               in
7739               RFC 1034, a style similar to that used in master files was
7740               employed
7741               in order to show the contents of RRs.  In this format, most RRs
7742               are shown on a single line, although continuation lines are
7743               possible
7744               using parentheses.
7745             </p>
7746 <p>
7747               The start of the line gives the owner of the RR.  If a line
7748               begins with a blank, then the owner is assumed to be the same as
7749               that of the previous RR.  Blank lines are often included for
7750               readability.
7751             </p>
7752 <p>
7753               Following the owner, we list the TTL, type, and class of the
7754               RR.  Class and type use the mnemonics defined above, and TTL is
7755               an integer before the type field.  In order to avoid ambiguity
7756               in
7757               parsing, type and class mnemonics are disjoint, TTLs are
7758               integers,
7759               and the type mnemonic is always last. The IN class and TTL
7760               values
7761               are often omitted from examples in the interests of clarity.
7762             </p>
7763 <p>
7764               The resource data or RDATA section of the RR are given using
7765               knowledge of the typical representation for the data.
7766             </p>
7767 <p>
7768               For example, we might show the RRs carried in a message as:
7769             </p>
7770 <div class="informaltable"><table border="1">
7771 <colgroup>
7772 <col>
7773 <col>
7774 <col>
7775 </colgroup>
7776 <tbody>
7777 <tr>
7778 <td>
7779                       <p>
7780                         <code class="literal">ISI.EDU.</code>
7781                       </p>
7782                     </td>
7783 <td>
7784                       <p>
7785                         <code class="literal">MX</code>
7786                       </p>
7787                     </td>
7788 <td>
7789                       <p>
7790                         <code class="literal">10 VENERA.ISI.EDU.</code>
7791                       </p>
7792                     </td>
7793 </tr>
7794 <tr>
7795 <td>
7796                       <p></p>
7797                     </td>
7798 <td>
7799                       <p>
7800                         <code class="literal">MX</code>
7801                       </p>
7802                     </td>
7803 <td>
7804                       <p>
7805                         <code class="literal">10 VAXA.ISI.EDU</code>
7806                       </p>
7807                     </td>
7808 </tr>
7809 <tr>
7810 <td>
7811                       <p>
7812                         <code class="literal">VENERA.ISI.EDU</code>
7813                       </p>
7814                     </td>
7815 <td>
7816                       <p>
7817                         <code class="literal">A</code>
7818                       </p>
7819                     </td>
7820 <td>
7821                       <p>
7822                         <code class="literal">128.9.0.32</code>
7823                       </p>
7824                     </td>
7825 </tr>
7826 <tr>
7827 <td>
7828                       <p></p>
7829                     </td>
7830 <td>
7831                       <p>
7832                         <code class="literal">A</code>
7833                       </p>
7834                     </td>
7835 <td>
7836                       <p>
7837                         <code class="literal">10.1.0.52</code>
7838                       </p>
7839                     </td>
7840 </tr>
7841 <tr>
7842 <td>
7843                       <p>
7844                         <code class="literal">VAXA.ISI.EDU</code>
7845                       </p>
7846                     </td>
7847 <td>
7848                       <p>
7849                         <code class="literal">A</code>
7850                       </p>
7851                     </td>
7852 <td>
7853                       <p>
7854                         <code class="literal">10.2.0.27</code>
7855                       </p>
7856                     </td>
7857 </tr>
7858 <tr>
7859 <td>
7860                       <p></p>
7861                     </td>
7862 <td>
7863                       <p>
7864                         <code class="literal">A</code>
7865                       </p>
7866                     </td>
7867 <td>
7868                       <p>
7869                         <code class="literal">128.9.0.33</code>
7870                       </p>
7871                     </td>
7872 </tr>
7873 </tbody>
7874 </table></div>
7875 <p>
7876               The MX RRs have an RDATA section which consists of a 16-bit
7877               number followed by a domain name.  The address RRs use a
7878               standard
7879               IP address format to contain a 32-bit internet address.
7880             </p>
7881 <p>
7882               The above example shows six RRs, with two RRs at each of three
7883               domain names.
7884             </p>
7885 <p>
7886               Similarly we might see:
7887             </p>
7888 <div class="informaltable"><table border="1">
7889 <colgroup>
7890 <col>
7891 <col>
7892 <col>
7893 </colgroup>
7894 <tbody>
7895 <tr>
7896 <td>
7897                       <p>
7898                         <code class="literal">XX.LCS.MIT.EDU.</code>
7899                       </p>
7900                     </td>
7901 <td>
7902                       <p>
7903                         <code class="literal">IN A</code>
7904                       </p>
7905                     </td>
7906 <td>
7907                       <p>
7908                         <code class="literal">10.0.0.44</code>
7909                       </p>
7910                     </td>
7911 </tr>
7912 <tr>
7913 <td> </td>
7914 <td>
7915                       <p>
7916                         <code class="literal">CH A</code>
7917                       </p>
7918                     </td>
7919 <td>
7920                       <p>
7921                         <code class="literal">MIT.EDU. 2420</code>
7922                       </p>
7923                     </td>
7924 </tr>
7925 </tbody>
7926 </table></div>
7927 <p>
7928               This example shows two addresses for
7929               <code class="literal">XX.LCS.MIT.EDU</code>, each of a different class.
7930             </p>
7931 </div>
7932 </div>
7933 <div class="sect2" lang="en">
7934 <div class="titlepage"><div><div><h3 class="title">
7935 <a name="id2595454"></a>Discussion of MX Records</h3></div></div></div>
7936 <p>
7937             As described above, domain servers store information as a
7938             series of resource records, each of which contains a particular
7939             piece of information about a given domain name (which is usually,
7940             but not always, a host). The simplest way to think of a RR is as
7941             a typed pair of data, a domain name matched with a relevant datum,
7942             and stored with some additional type information to help systems
7943             determine when the RR is relevant.
7944           </p>
7945 <p>
7946             MX records are used to control delivery of email. The data
7947             specified in the record is a priority and a domain name. The
7948             priority
7949             controls the order in which email delivery is attempted, with the
7950             lowest number first. If two priorities are the same, a server is
7951             chosen randomly. If no servers at a given priority are responding,
7952             the mail transport agent will fall back to the next largest
7953             priority.
7954             Priority numbers do not have any absolute meaning &#8212; they are
7955             relevant
7956             only respective to other MX records for that domain name. The
7957             domain
7958             name given is the machine to which the mail will be delivered.
7959             It <span class="emphasis"><em>must</em></span> have an associated address record
7960             (A or AAAA) &#8212; CNAME is not sufficient.
7961           </p>
7962 <p>
7963             For a given domain, if there is both a CNAME record and an
7964             MX record, the MX record is in error, and will be ignored.
7965             Instead,
7966             the mail will be delivered to the server specified in the MX
7967             record
7968             pointed to by the CNAME.
7969             For example:
7970           </p>
7971 <div class="informaltable"><table border="1">
7972 <colgroup>
7973 <col>
7974 <col>
7975 <col>
7976 <col>
7977 <col>
7978 </colgroup>
7979 <tbody>
7980 <tr>
7981 <td>
7982                     <p>
7983                       <code class="literal">example.com.</code>
7984                     </p>
7985                   </td>
7986 <td>
7987                     <p>
7988                       <code class="literal">IN</code>
7989                     </p>
7990                   </td>
7991 <td>
7992                     <p>
7993                       <code class="literal">MX</code>
7994                     </p>
7995                   </td>
7996 <td>
7997                     <p>
7998                       <code class="literal">10</code>
7999                     </p>
8000                   </td>
8001 <td>
8002                     <p>
8003                       <code class="literal">mail.example.com.</code>
8004                     </p>
8005                   </td>
8006 </tr>
8007 <tr>
8008 <td>
8009                     <p></p>
8010                   </td>
8011 <td>
8012                     <p>
8013                       <code class="literal">IN</code>
8014                     </p>
8015                   </td>
8016 <td>
8017                     <p>
8018                       <code class="literal">MX</code>
8019                     </p>
8020                   </td>
8021 <td>
8022                     <p>
8023                       <code class="literal">10</code>
8024                     </p>
8025                   </td>
8026 <td>
8027                     <p>
8028                       <code class="literal">mail2.example.com.</code>
8029                     </p>
8030                   </td>
8031 </tr>
8032 <tr>
8033 <td>
8034                     <p></p>
8035                   </td>
8036 <td>
8037                     <p>
8038                       <code class="literal">IN</code>
8039                     </p>
8040                   </td>
8041 <td>
8042                     <p>
8043                       <code class="literal">MX</code>
8044                     </p>
8045                   </td>
8046 <td>
8047                     <p>
8048                       <code class="literal">20</code>
8049                     </p>
8050                   </td>
8051 <td>
8052                     <p>
8053                       <code class="literal">mail.backup.org.</code>
8054                     </p>
8055                   </td>
8056 </tr>
8057 <tr>
8058 <td>
8059                     <p>
8060                       <code class="literal">mail.example.com.</code>
8061                     </p>
8062                   </td>
8063 <td>
8064                     <p>
8065                       <code class="literal">IN</code>
8066                     </p>
8067                   </td>
8068 <td>
8069                     <p>
8070                       <code class="literal">A</code>
8071                     </p>
8072                   </td>
8073 <td>
8074                     <p>
8075                       <code class="literal">10.0.0.1</code>
8076                     </p>
8077                   </td>
8078 <td>
8079                     <p></p>
8080                   </td>
8081 </tr>
8082 <tr>
8083 <td>
8084                     <p>
8085                       <code class="literal">mail2.example.com.</code>
8086                     </p>
8087                   </td>
8088 <td>
8089                     <p>
8090                       <code class="literal">IN</code>
8091                     </p>
8092                   </td>
8093 <td>
8094                     <p>
8095                       <code class="literal">A</code>
8096                     </p>
8097                   </td>
8098 <td>
8099                     <p>
8100                       <code class="literal">10.0.0.2</code>
8101                     </p>
8102                   </td>
8103 <td>
8104                     <p></p>
8105                   </td>
8106 </tr>
8107 </tbody>
8108 </table></div>
8109 <p>
8110             Mail delivery will be attempted to <code class="literal">mail.example.com</code> and
8111             <code class="literal">mail2.example.com</code> (in
8112             any order), and if neither of those succeed, delivery to <code class="literal">mail.backup.org</code> will
8113             be attempted.
8114           </p>
8115 </div>
8116 <div class="sect2" lang="en">
8117 <div class="titlepage"><div><div><h3 class="title">
8118 <a name="Setting_TTLs"></a>Setting TTLs</h3></div></div></div>
8119 <p>
8120             The time-to-live of the RR field is a 32-bit integer represented
8121             in units of seconds, and is primarily used by resolvers when they
8122             cache RRs. The TTL describes how long a RR can be cached before it
8123             should be discarded. The following three types of TTL are
8124             currently
8125             used in a zone file.
8126           </p>
8127 <div class="informaltable"><table border="1">
8128 <colgroup>
8129 <col>
8130 <col>
8131 </colgroup>
8132 <tbody>
8133 <tr>
8134 <td>
8135                     <p>
8136                       SOA
8137                     </p>
8138                   </td>
8139 <td>
8140                     <p>
8141                       The last field in the SOA is the negative
8142                       caching TTL. This controls how long other servers will
8143                       cache no-such-domain
8144                       (NXDOMAIN) responses from you.
8145                     </p>
8146                     <p>
8147                       The maximum time for
8148                       negative caching is 3 hours (3h).
8149                     </p>
8150                   </td>
8151 </tr>
8152 <tr>
8153 <td>
8154                     <p>
8155                       $TTL
8156                     </p>
8157                   </td>
8158 <td>
8159                     <p>
8160                       The $TTL directive at the top of the
8161                       zone file (before the SOA) gives a default TTL for every
8162                       RR without
8163                       a specific TTL set.
8164                     </p>
8165                   </td>
8166 </tr>
8167 <tr>
8168 <td>
8169                     <p>
8170                       RR TTLs
8171                     </p>
8172                   </td>
8173 <td>
8174                     <p>
8175                       Each RR can have a TTL as the second
8176                       field in the RR, which will control how long other
8177                       servers can cache
8178                       the it.
8179                     </p>
8180                   </td>
8181 </tr>
8182 </tbody>
8183 </table></div>
8184 <p>
8185             All of these TTLs default to units of seconds, though units
8186             can be explicitly specified, for example, <code class="literal">1h30m</code>.
8187           </p>
8188 </div>
8189 <div class="sect2" lang="en">
8190 <div class="titlepage"><div><div><h3 class="title">
8191 <a name="id2596070"></a>Inverse Mapping in IPv4</h3></div></div></div>
8192 <p>
8193             Reverse name resolution (that is, translation from IP address
8194             to name) is achieved by means of the <span class="emphasis"><em>in-addr.arpa</em></span> domain
8195             and PTR records. Entries in the in-addr.arpa domain are made in
8196             least-to-most significant order, read left to right. This is the
8197             opposite order to the way IP addresses are usually written. Thus,
8198             a machine with an IP address of 10.1.2.3 would have a
8199             corresponding
8200             in-addr.arpa name of
8201             3.2.1.10.in-addr.arpa. This name should have a PTR resource record
8202             whose data field is the name of the machine or, optionally,
8203             multiple
8204             PTR records if the machine has more than one name. For example,
8205             in the [<span class="optional">example.com</span>] domain:
8206           </p>
8207 <div class="informaltable"><table border="1">
8208 <colgroup>
8209 <col>
8210 <col>
8211 </colgroup>
8212 <tbody>
8213 <tr>
8214 <td>
8215                     <p>
8216                       <code class="literal">$ORIGIN</code>
8217                     </p>
8218                   </td>
8219 <td>
8220                     <p>
8221                       <code class="literal">2.1.10.in-addr.arpa</code>
8222                     </p>
8223                   </td>
8224 </tr>
8225 <tr>
8226 <td>
8227                     <p>
8228                       <code class="literal">3</code>
8229                     </p>
8230                   </td>
8231 <td>
8232                     <p>
8233                       <code class="literal">IN PTR foo.example.com.</code>
8234                     </p>
8235                   </td>
8236 </tr>
8237 </tbody>
8238 </table></div>
8239 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
8240 <h3 class="title">Note</h3>
8241 <p>
8242               The <span><strong class="command">$ORIGIN</strong></span> lines in the examples
8243               are for providing context to the examples only &#8212; they do not
8244               necessarily
8245               appear in the actual usage. They are only used here to indicate
8246               that the example is relative to the listed origin.
8247             </p>
8248 </div>
8249 </div>
8250 <div class="sect2" lang="en">
8251 <div class="titlepage"><div><div><h3 class="title">
8252 <a name="id2596197"></a>Other Zone File Directives</h3></div></div></div>
8253 <p>
8254             The Master File Format was initially defined in RFC 1035 and
8255             has subsequently been extended. While the Master File Format
8256             itself
8257             is class independent all records in a Master File must be of the
8258             same
8259             class.
8260           </p>
8261 <p>
8262             Master File Directives include <span><strong class="command">$ORIGIN</strong></span>, <span><strong class="command">$INCLUDE</strong></span>,
8263             and <span><strong class="command">$TTL.</strong></span>
8264           </p>
8265 <div class="sect3" lang="en">
8266 <div class="titlepage"><div><div><h4 class="title">
8267 <a name="id2596219"></a>The <span><strong class="command">@</strong></span> (at-sign)</h4></div></div></div>
8268 <p>
8269               When used in the label (or name) field, the asperand or
8270               at-sign (@) symbol represents the current origin.
8271               At the start of the zone file, it is the
8272               &lt;<code class="varname">zone_name</code>&gt; (followed by
8273               trailing dot).
8274             </p>
8275 </div>
8276 <div class="sect3" lang="en">
8277 <div class="titlepage"><div><div><h4 class="title">
8278 <a name="id2596235"></a>The <span><strong class="command">$ORIGIN</strong></span> Directive</h4></div></div></div>
8279 <p>
8280               Syntax: <span><strong class="command">$ORIGIN</strong></span>
8281               <em class="replaceable"><code>domain-name</code></em>
8282               [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
8283             </p>
8284 <p><span><strong class="command">$ORIGIN</strong></span>
8285               sets the domain name that will be appended to any
8286               unqualified records. When a zone is first read in there
8287               is an implicit <span><strong class="command">$ORIGIN</strong></span>
8288               &lt;<code class="varname">zone_name</code>&gt;<span><strong class="command">.</strong></span>
8289               (followed by trailing dot).
8290               The current <span><strong class="command">$ORIGIN</strong></span> is appended to
8291               the domain specified in the <span><strong class="command">$ORIGIN</strong></span>
8292               argument if it is not absolute.
8293             </p>
8294 <pre class="programlisting">
8295 $ORIGIN example.com.
8296 WWW     CNAME   MAIN-SERVER
8297 </pre>
8298 <p>
8299               is equivalent to
8300             </p>
8301 <pre class="programlisting">
8302 WWW.EXAMPLE.COM. CNAME MAIN-SERVER.EXAMPLE.COM.
8303 </pre>
8304 </div>
8305 <div class="sect3" lang="en">
8306 <div class="titlepage"><div><div><h4 class="title">
8307 <a name="id2596296"></a>The <span><strong class="command">$INCLUDE</strong></span> Directive</h4></div></div></div>
8308 <p>
8309               Syntax: <span><strong class="command">$INCLUDE</strong></span>
8310               <em class="replaceable"><code>filename</code></em>
8311               [<span class="optional">
8312 <em class="replaceable"><code>origin</code></em> </span>]
8313               [<span class="optional"> <em class="replaceable"><code>comment</code></em> </span>]
8314             </p>
8315 <p>
8316               Read and process the file <code class="filename">filename</code> as
8317               if it were included into the file at this point.  If <span><strong class="command">origin</strong></span> is
8318               specified the file is processed with <span><strong class="command">$ORIGIN</strong></span> set
8319               to that value, otherwise the current <span><strong class="command">$ORIGIN</strong></span> is
8320               used.
8321             </p>
8322 <p>
8323               The origin and the current domain name
8324               revert to the values they had prior to the <span><strong class="command">$INCLUDE</strong></span> once
8325               the file has been read.
8326             </p>
8327 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
8328 <h3 class="title">Note</h3>
8329 <p>
8330                 RFC 1035 specifies that the current origin should be restored
8331                 after
8332                 an <span><strong class="command">$INCLUDE</strong></span>, but it is silent
8333                 on whether the current
8334                 domain name should also be restored.  BIND 9 restores both of
8335                 them.
8336                 This could be construed as a deviation from RFC 1035, a
8337                 feature, or both.
8338               </p>
8339 </div>
8340 </div>
8341 <div class="sect3" lang="en">
8342 <div class="titlepage"><div><div><h4 class="title">
8343 <a name="id2596365"></a>The <span><strong class="command">$TTL</strong></span> Directive</h4></div></div></div>
8344 <p>
8345               Syntax: <span><strong class="command">$TTL</strong></span>
8346               <em class="replaceable"><code>default-ttl</code></em>
8347               [<span class="optional">
8348 <em class="replaceable"><code>comment</code></em> </span>]
8349             </p>
8350 <p>
8351               Set the default Time To Live (TTL) for subsequent records
8352               with undefined TTLs. Valid TTLs are of the range 0-2147483647
8353               seconds.
8354             </p>
8355 <p><span><strong class="command">$TTL</strong></span>
8356                is defined in RFC 2308.
8357             </p>
8358 </div>
8359 </div>
8360 <div class="sect2" lang="en">
8361 <div class="titlepage"><div><div><h3 class="title">
8362 <a name="id2596470"></a><acronym class="acronym">BIND</acronym> Master File Extension: the  <span><strong class="command">$GENERATE</strong></span> Directive</h3></div></div></div>
8363 <p>
8364             Syntax: <span><strong class="command">$GENERATE</strong></span>
8365             <em class="replaceable"><code>range</code></em>
8366             <em class="replaceable"><code>lhs</code></em>
8367             [<span class="optional"><em class="replaceable"><code>ttl</code></em></span>]
8368             [<span class="optional"><em class="replaceable"><code>class</code></em></span>]
8369             <em class="replaceable"><code>type</code></em>
8370             <em class="replaceable"><code>rhs</code></em>
8371             [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
8372           </p>
8373 <p><span><strong class="command">$GENERATE</strong></span>
8374             is used to create a series of resource records that only
8375             differ from each other by an
8376             iterator. <span><strong class="command">$GENERATE</strong></span> can be used to
8377             easily generate the sets of records required to support
8378             sub /24 reverse delegations described in RFC 2317:
8379             Classless IN-ADDR.ARPA delegation.
8380           </p>
8381 <pre class="programlisting">$ORIGIN 0.0.192.IN-ADDR.ARPA.
8382 $GENERATE 1-2 @ NS SERVER$.EXAMPLE.
8383 $GENERATE 1-127 $ CNAME $.0</pre>
8384 <p>
8385             is equivalent to
8386           </p>
8387 <pre class="programlisting">0.0.0.192.IN-ADDR.ARPA. NS SERVER1.EXAMPLE.
8388 0.0.0.192.IN-ADDR.ARPA. NS SERVER2.EXAMPLE.
8389 1.0.0.192.IN-ADDR.ARPA. CNAME 1.0.0.0.192.IN-ADDR.ARPA.
8390 2.0.0.192.IN-ADDR.ARPA. CNAME 2.0.0.0.192.IN-ADDR.ARPA.
8391 ...
8392 127.0.0.192.IN-ADDR.ARPA. CNAME 127.0.0.0.192.IN-ADDR.ARPA.
8393 </pre>
8394 <p>
8395             Generate a set of A and MX records.  Note the MX's right hand
8396             side is a quoted string.  The quotes will be stripped when the
8397             right hand side is processed.
8398            </p>
8399 <pre class="programlisting">
8400 $ORIGIN EXAMPLE.
8401 $GENERATE 1-127 HOST-$ A 1.2.3.$
8402 $GENERATE 1-127 HOST-$ MX "0 ."</pre>
8403 <p>
8404             is equivalent to
8405           </p>
8406 <pre class="programlisting">HOST-1.EXAMPLE.   A  1.2.3.1
8407 HOST-1.EXAMPLE.   MX 0 .
8408 HOST-2.EXAMPLE.   A  1.2.3.2
8409 HOST-2.EXAMPLE.   MX 0 .
8410 HOST-3.EXAMPLE.   A  1.2.3.3
8411 HOST-3.EXAMPLE.   MX 0 .
8412 ...
8413 HOST-127.EXAMPLE. A  1.2.3.127
8414 HOST-127.EXAMPLE. MX 0 .
8415 </pre>
8416 <div class="informaltable"><table border="1">
8417 <colgroup>
8418 <col>
8419 <col>
8420 </colgroup>
8421 <tbody>
8422 <tr>
8423 <td>
8424                     <p><span><strong class="command">range</strong></span></p>
8425                   </td>
8426 <td>
8427                     <p>
8428                       This can be one of two forms: start-stop
8429                       or start-stop/step. If the first form is used, then step
8430                       is set to
8431                       1. All of start, stop and step must be positive.
8432                     </p>
8433                   </td>
8434 </tr>
8435 <tr>
8436 <td>
8437                     <p><span><strong class="command">lhs</strong></span></p>
8438                   </td>
8439 <td>
8440                     <p>This
8441                       describes the owner name of the resource records
8442                       to be created.  Any single <span><strong class="command">$</strong></span>
8443                       (dollar sign)
8444                       symbols within the <span><strong class="command">lhs</strong></span> string
8445                       are replaced by the iterator value.
8446
8447                       To get a $ in the output, you need to escape the
8448                       <span><strong class="command">$</strong></span> using a backslash
8449                       <span><strong class="command">\</strong></span>,
8450                       e.g. <span><strong class="command">\$</strong></span>. The
8451                       <span><strong class="command">$</strong></span> may optionally be followed
8452                       by modifiers which change the offset from the
8453                       iterator, field width and base.
8454
8455                       Modifiers are introduced by a
8456                       <span><strong class="command">{</strong></span> (left brace) immediately following the
8457                       <span><strong class="command">$</strong></span> as
8458                       <span><strong class="command">${offset[,width[,base]]}</strong></span>.
8459                       For example, <span><strong class="command">${-20,3,d}</strong></span>
8460                       subtracts 20 from the current value, prints the
8461                       result as a decimal in a zero-padded field of
8462                       width 3.
8463
8464                       Available output forms are decimal
8465                       (<span><strong class="command">d</strong></span>), octal
8466                       (<span><strong class="command">o</strong></span>), hexadecimal
8467                       (<span><strong class="command">x</strong></span> or <span><strong class="command">X</strong></span>
8468                       for uppercase) and nibble
8469                       (<span><strong class="command">n</strong></span> or <span><strong class="command">N</strong></span>\
8470                       for uppercase).  The default modifier is
8471                       <span><strong class="command">${0,0,d}</strong></span>.  If the
8472                       <span><strong class="command">lhs</strong></span> is not absolute, the
8473                       current <span><strong class="command">$ORIGIN</strong></span> is appended
8474                       to the name.
8475                     </p>
8476                     <p>
8477                       In nibble mode the value will be treated as
8478                       if it was a reversed hexadecimal string
8479                       with each hexadecimal digit as a separate
8480                       label.  The width field includes the label
8481                       separator.
8482                     </p>
8483                     <p>
8484                       For compatibility with earlier versions,
8485                       <span><strong class="command">$$</strong></span> is still recognized as
8486                       indicating a literal $ in the output.
8487                     </p>
8488                   </td>
8489 </tr>
8490 <tr>
8491 <td>
8492                     <p><span><strong class="command">ttl</strong></span></p>
8493                   </td>
8494 <td>
8495                     <p>
8496                       Specifies the time-to-live of the generated records. If
8497                       not specified this will be inherited using the
8498                       normal TTL inheritance rules.
8499                     </p>
8500                     <p><span><strong class="command">class</strong></span>
8501                       and <span><strong class="command">ttl</strong></span> can be
8502                       entered in either order.
8503                     </p>
8504                   </td>
8505 </tr>
8506 <tr>
8507 <td>
8508                     <p><span><strong class="command">class</strong></span></p>
8509                   </td>
8510 <td>
8511                     <p>
8512                       Specifies the class of the generated records.
8513                       This must match the zone class if it is
8514                       specified.
8515                     </p>
8516                     <p><span><strong class="command">class</strong></span>
8517                       and <span><strong class="command">ttl</strong></span> can be
8518                       entered in either order.
8519                     </p>
8520                   </td>
8521 </tr>
8522 <tr>
8523 <td>
8524                     <p><span><strong class="command">type</strong></span></p>
8525                   </td>
8526 <td>
8527                     <p>
8528                       Any valid type.
8529                     </p>
8530                   </td>
8531 </tr>
8532 <tr>
8533 <td>
8534                     <p><span><strong class="command">rhs</strong></span></p>
8535                   </td>
8536 <td>
8537                     <p>
8538                       <span><strong class="command">rhs</strong></span>, optionally, quoted string.
8539                     </p>
8540                   </td>
8541 </tr>
8542 </tbody>
8543 </table></div>
8544 <p>
8545             The <span><strong class="command">$GENERATE</strong></span> directive is a <acronym class="acronym">BIND</acronym> extension
8546             and not part of the standard zone file format.
8547           </p>
8548 <p>
8549             BIND 8 does not support the optional TTL and CLASS fields.
8550           </p>
8551 </div>
8552 <div class="sect2" lang="en">
8553 <div class="titlepage"><div><div><h3 class="title">
8554 <a name="zonefile_format"></a>Additional File Formats</h3></div></div></div>
8555 <p>
8556             In addition to the standard textual format, BIND 9
8557             supports the ability to read or dump to zone files in
8558             other formats.  The <code class="constant">raw</code> format is
8559             currently available as an additional format.  It is a
8560             binary format representing BIND 9's internal data
8561             structure directly, thereby remarkably improving the
8562             loading time.
8563           </p>
8564 <p>
8565             For a primary server, a zone file in the
8566             <code class="constant">raw</code> format is expected to be
8567             generated from a textual zone file by the
8568             <span><strong class="command">named-compilezone</strong></span> command.  For a
8569             secondary server or for a dynamic zone, it is automatically
8570             generated (if this format is specified by the
8571             <span><strong class="command">masterfile-format</strong></span> option) when
8572             <span><strong class="command">named</strong></span> dumps the zone contents after
8573             zone transfer or when applying prior updates.
8574           </p>
8575 <p>
8576             If a zone file in a binary format needs manual modification,
8577             it first must be converted to a textual form by the
8578             <span><strong class="command">named-compilezone</strong></span> command.  All
8579             necessary modification should go to the text file, which
8580             should then be converted to the binary form by the
8581             <span><strong class="command">named-compilezone</strong></span> command again.
8582           </p>
8583 <p>
8584              Although the <code class="constant">raw</code> format uses the
8585              network byte order and avoids architecture-dependent
8586              data alignment so that it is as much portable as
8587              possible, it is primarily expected to be used inside
8588              the same single system.  In order to export a zone
8589              file in the <code class="constant">raw</code> format or make a
8590              portable backup of the file, it is recommended to
8591              convert the file to the standard textual representation.
8592           </p>
8593 </div>
8594 </div>
8595 <div class="sect1" lang="en">
8596 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
8597 <a name="statistics"></a>BIND9 Statistics</h2></div></div></div>
8598 <p>
8599           <acronym class="acronym">BIND</acronym> 9 maintains lots of statistics
8600           information and provides several interfaces for users to
8601           get access to the statistics.
8602           The available statistics include all statistics counters
8603           that were available in <acronym class="acronym">BIND</acronym> 8 and
8604           are meaningful in <acronym class="acronym">BIND</acronym> 9,
8605           and other information that is considered useful.
8606         </p>
8607 <p>
8608           The statistics information is categorized into the following
8609           sections.
8610         </p>
8611 <div class="informaltable"><table border="1">
8612 <colgroup>
8613 <col>
8614 <col>
8615 </colgroup>
8616 <tbody>
8617 <tr>
8618 <td>
8619                   <p>Incoming Requests</p>
8620                 </td>
8621 <td>
8622                   <p>
8623                     The number of incoming DNS requests for each OPCODE.
8624                   </p>
8625                 </td>
8626 </tr>
8627 <tr>
8628 <td>
8629                   <p>Incoming Queries</p>
8630                 </td>
8631 <td>
8632                   <p>
8633                     The number of incoming queries for each RR type.
8634                   </p>
8635                 </td>
8636 </tr>
8637 <tr>
8638 <td>
8639                   <p>Outgoing Queries</p>
8640                 </td>
8641 <td>
8642                   <p>
8643                     The number of outgoing queries for each RR
8644                     type sent from the internal resolver.
8645                     Maintained per view.
8646                   </p>
8647                 </td>
8648 </tr>
8649 <tr>
8650 <td>
8651                   <p>Name Server Statistics</p>
8652                 </td>
8653 <td>
8654                   <p>
8655                     Statistics counters about incoming request processing.
8656                   </p>
8657                 </td>
8658 </tr>
8659 <tr>
8660 <td>
8661                   <p>Zone Maintenance Statistics</p>
8662                 </td>
8663 <td>
8664                   <p>
8665                     Statistics counters regarding zone maintenance
8666                     operations such as zone transfers.
8667                   </p>
8668                 </td>
8669 </tr>
8670 <tr>
8671 <td>
8672                   <p>Resolver Statistics</p>
8673                 </td>
8674 <td>
8675                   <p>
8676                     Statistics counters about name resolution
8677                     performed in the internal resolver.
8678                     Maintained per view.
8679                   </p>
8680                 </td>
8681 </tr>
8682 <tr>
8683 <td>
8684                   <p>Cache DB RRsets</p>
8685                 </td>
8686 <td>
8687                   <p>
8688                     The number of RRsets per RR type and nonexistent
8689                     names stored in the cache database.
8690                     If the exclamation mark (!) is printed for a RR
8691                     type, it means that particular type of RRset is
8692                     known to be nonexistent (this is also known as
8693                     "NXRRSET").
8694                     Maintained per view.
8695                   </p>
8696                 </td>
8697 </tr>
8698 <tr>
8699 <td>
8700                   <p>Socket I/O Statistics</p>
8701                 </td>
8702 <td>
8703                   <p>
8704                     Statistics counters about network related events.
8705                   </p>
8706                 </td>
8707 </tr>
8708 </tbody>
8709 </table></div>
8710 <p>
8711           A subset of Name Server Statistics is collected and shown
8712           per zone for which the server has the authority when
8713           <span><strong class="command">zone-statistics</strong></span> is set to
8714           <strong class="userinput"><code>yes</code></strong>.
8715           These statistics counters are shown with their zone and view
8716           names.
8717           In some cases the view names are omitted for the default view.
8718         </p>
8719 <p>
8720           There are currently two user interfaces to get access to the
8721           statistics.
8722           One is in the plain text format dumped to the file specified
8723           by the <span><strong class="command">statistics-file</strong></span> configuration option.
8724           The other is remotely accessible via a statistics channel
8725           when the <span><strong class="command">statistics-channels</strong></span> statement
8726           is specified in the configuration file
8727           (see <a href="Bv9ARM.ch06.html#statschannels" title="statistics-channels Statement Grammar">the section called &#8220;<span><strong class="command">statistics-channels</strong></span> Statement Grammar&#8221;</a>.)
8728         </p>
8729 <div class="sect3" lang="en">
8730 <div class="titlepage"><div><div><h4 class="title">
8731 <a name="statsfile"></a>The Statistics File</h4></div></div></div>
8732 <p>
8733             The text format statistics dump begins with a line, like:
8734           </p>
8735 <p>
8736             <span><strong class="command">+++ Statistics Dump +++ (973798949)</strong></span>
8737           </p>
8738 <p>
8739             The number in parentheses is a standard
8740             Unix-style timestamp, measured as seconds since January 1, 1970.
8741
8742             Following
8743             that line is a set of statistics information, which is categorized
8744             as described above.
8745             Each section begins with a line, like:
8746           </p>
8747 <p>
8748             <span><strong class="command">++ Name Server Statistics ++</strong></span>
8749           </p>
8750 <p>
8751             Each section consists of lines, each containing the statistics
8752             counter value followed by its textual description.
8753             See below for available counters.
8754             For brevity, counters that have a value of 0 are not shown
8755             in the statistics file.
8756           </p>
8757 <p>
8758             The statistics dump ends with the line where the
8759             number is identical to the number in the beginning line; for example:
8760           </p>
8761 <p>
8762             <span><strong class="command">--- Statistics Dump --- (973798949)</strong></span>
8763           </p>
8764 </div>
8765 <div class="sect2" lang="en">
8766 <div class="titlepage"><div><div><h3 class="title">
8767 <a name="statistics_counters"></a>Statistics Counters</h3></div></div></div>
8768 <p>
8769             The following tables summarize statistics counters that
8770             <acronym class="acronym">BIND</acronym> 9 provides.
8771             For each row of the tables, the leftmost column is the
8772             abbreviated symbol name of that counter.
8773             These symbols are shown in the statistics information
8774             accessed via an HTTP statistics channel.
8775             The rightmost column gives the description of the counter,
8776             which is also shown in the statistics file
8777             (but, in this document, possibly with slight modification
8778             for better readability).
8779             Additional notes may also be provided in this column.
8780             When a middle column exists between these two columns,
8781             it gives the corresponding counter name of the
8782             <acronym class="acronym">BIND</acronym> 8 statistics, if applicable.
8783           </p>
8784 <div class="sect3" lang="en">
8785 <div class="titlepage"><div><div><h4 class="title">
8786 <a name="id2597560"></a>Name Server Statistics Counters</h4></div></div></div>
8787 <div class="informaltable"><table border="1">
8788 <colgroup>
8789 <col>
8790 <col>
8791 <col>
8792 </colgroup>
8793 <tbody>
8794 <tr>
8795 <td>
8796                       <p>
8797                         <span class="emphasis"><em>Symbol</em></span>
8798                       </p>
8799                     </td>
8800 <td>
8801                       <p>
8802                         <span class="emphasis"><em>BIND8 Symbol</em></span>
8803                       </p>
8804                     </td>
8805 <td>
8806                       <p>
8807                         <span class="emphasis"><em>Description</em></span>
8808                       </p>
8809                     </td>
8810 </tr>
8811 <tr>
8812 <td>
8813                       <p><span><strong class="command">Requestv4</strong></span></p>
8814                     </td>
8815 <td>
8816                       <p><span><strong class="command">RQ</strong></span></p>
8817                     </td>
8818 <td>
8819                       <p>
8820                         IPv4 requests received.
8821                         Note: this also counts non query requests.
8822                       </p>
8823                     </td>
8824 </tr>
8825 <tr>
8826 <td>
8827                       <p><span><strong class="command">Requestv6</strong></span></p>
8828                     </td>
8829 <td>
8830                       <p><span><strong class="command">RQ</strong></span></p>
8831                     </td>
8832 <td>
8833                       <p>
8834                         IPv6 requests received.
8835                         Note: this also counts non query requests.
8836                       </p>
8837                     </td>
8838 </tr>
8839 <tr>
8840 <td>
8841                       <p><span><strong class="command">ReqEdns0</strong></span></p>
8842                     </td>
8843 <td>
8844                       <p><span><strong class="command"></strong></span></p>
8845                     </td>
8846 <td>
8847                       <p>
8848                         Requests with EDNS(0) received.
8849                       </p>
8850                     </td>
8851 </tr>
8852 <tr>
8853 <td>
8854                       <p><span><strong class="command">ReqBadEDNSVer</strong></span></p>
8855                     </td>
8856 <td>
8857                       <p><span><strong class="command"></strong></span></p>
8858                     </td>
8859 <td>
8860                       <p>
8861                         Requests with unsupported EDNS version received.
8862                       </p>
8863                     </td>
8864 </tr>
8865 <tr>
8866 <td>
8867                       <p><span><strong class="command">ReqTSIG</strong></span></p>
8868                     </td>
8869 <td>
8870                       <p><span><strong class="command"></strong></span></p>
8871                     </td>
8872 <td>
8873                       <p>
8874                         Requests with TSIG received.
8875                       </p>
8876                     </td>
8877 </tr>
8878 <tr>
8879 <td>
8880                       <p><span><strong class="command">ReqSIG0</strong></span></p>
8881                     </td>
8882 <td>
8883                       <p><span><strong class="command"></strong></span></p>
8884                     </td>
8885 <td>
8886                       <p>
8887                         Requests with SIG(0) received.
8888                       </p>
8889                     </td>
8890 </tr>
8891 <tr>
8892 <td>
8893                       <p><span><strong class="command">ReqBadSIG</strong></span></p>
8894                     </td>
8895 <td>
8896                       <p><span><strong class="command"></strong></span></p>
8897                     </td>
8898 <td>
8899                       <p>
8900                         Requests with invalid (TSIG or SIG(0)) signature.
8901                       </p>
8902                     </td>
8903 </tr>
8904 <tr>
8905 <td>
8906                       <p><span><strong class="command">ReqTCP</strong></span></p>
8907                     </td>
8908 <td>
8909                       <p><span><strong class="command">RTCP</strong></span></p>
8910                     </td>
8911 <td>
8912                       <p>
8913                         TCP requests received.
8914                       </p>
8915                     </td>
8916 </tr>
8917 <tr>
8918 <td>
8919                       <p><span><strong class="command">AuthQryRej</strong></span></p>
8920                     </td>
8921 <td>
8922                       <p><span><strong class="command">RUQ</strong></span></p>
8923                     </td>
8924 <td>
8925                       <p>
8926                         Authoritative (non recursive) queries rejected.
8927                       </p>
8928                     </td>
8929 </tr>
8930 <tr>
8931 <td>
8932                       <p><span><strong class="command">RecQryRej</strong></span></p>
8933                     </td>
8934 <td>
8935                       <p><span><strong class="command">RURQ</strong></span></p>
8936                     </td>
8937 <td>
8938                       <p>
8939                         Recursive queries rejected.
8940                       </p>
8941                     </td>
8942 </tr>
8943 <tr>
8944 <td>
8945                       <p><span><strong class="command">XfrRej</strong></span></p>
8946                     </td>
8947 <td>
8948                       <p><span><strong class="command">RUXFR</strong></span></p>
8949                     </td>
8950 <td>
8951                       <p>
8952                         Zone transfer requests rejected.
8953                       </p>
8954                     </td>
8955 </tr>
8956 <tr>
8957 <td>
8958                       <p><span><strong class="command">UpdateRej</strong></span></p>
8959                     </td>
8960 <td>
8961                       <p><span><strong class="command">RUUpd</strong></span></p>
8962                     </td>
8963 <td>
8964                       <p>
8965                         Dynamic update requests rejected.
8966                       </p>
8967                     </td>
8968 </tr>
8969 <tr>
8970 <td>
8971                       <p><span><strong class="command">Response</strong></span></p>
8972                     </td>
8973 <td>
8974                       <p><span><strong class="command">SAns</strong></span></p>
8975                     </td>
8976 <td>
8977                       <p>
8978                         Responses sent.
8979                       </p>
8980                     </td>
8981 </tr>
8982 <tr>
8983 <td>
8984                       <p><span><strong class="command">RespTruncated</strong></span></p>
8985                     </td>
8986 <td>
8987                       <p><span><strong class="command"></strong></span></p>
8988                     </td>
8989 <td>
8990                       <p>
8991                         Truncated responses sent.
8992                       </p>
8993                     </td>
8994 </tr>
8995 <tr>
8996 <td>
8997                       <p><span><strong class="command">RespEDNS0</strong></span></p>
8998                     </td>
8999 <td>
9000                       <p><span><strong class="command"></strong></span></p>
9001                     </td>
9002 <td>
9003                       <p>
9004                         Responses with EDNS(0) sent.
9005                       </p>
9006                     </td>
9007 </tr>
9008 <tr>
9009 <td>
9010                       <p><span><strong class="command">RespTSIG</strong></span></p>
9011                     </td>
9012 <td>
9013                       <p><span><strong class="command"></strong></span></p>
9014                     </td>
9015 <td>
9016                       <p>
9017                         Responses with TSIG sent.
9018                       </p>
9019                     </td>
9020 </tr>
9021 <tr>
9022 <td>
9023                       <p><span><strong class="command">RespSIG0</strong></span></p>
9024                     </td>
9025 <td>
9026                       <p><span><strong class="command"></strong></span></p>
9027                     </td>
9028 <td>
9029                       <p>
9030                         Responses with SIG(0) sent.
9031                       </p>
9032                     </td>
9033 </tr>
9034 <tr>
9035 <td>
9036                       <p><span><strong class="command">QrySuccess</strong></span></p>
9037                     </td>
9038 <td>
9039                       <p><span><strong class="command"></strong></span></p>
9040                     </td>
9041 <td>
9042                       <p>
9043                         Queries resulted in a successful answer.
9044                         This means the query which returns a NOERROR response
9045                         with at least one answer RR.
9046                         This corresponds to the
9047                         <span><strong class="command">success</strong></span> counter
9048                         of previous versions of
9049                         <acronym class="acronym">BIND</acronym> 9.
9050                       </p>
9051                     </td>
9052 </tr>
9053 <tr>
9054 <td>
9055                       <p><span><strong class="command">QryAuthAns</strong></span></p>
9056                     </td>
9057 <td>
9058                       <p><span><strong class="command"></strong></span></p>
9059                     </td>
9060 <td>
9061                       <p>
9062                         Queries resulted in authoritative answer.
9063                       </p>
9064                     </td>
9065 </tr>
9066 <tr>
9067 <td>
9068                       <p><span><strong class="command">QryNoauthAns</strong></span></p>
9069                     </td>
9070 <td>
9071                       <p><span><strong class="command">SNaAns</strong></span></p>
9072                     </td>
9073 <td>
9074                       <p>
9075                         Queries resulted in non authoritative answer.
9076                       </p>
9077                     </td>
9078 </tr>
9079 <tr>
9080 <td>
9081                       <p><span><strong class="command">QryReferral</strong></span></p>
9082                     </td>
9083 <td>
9084                       <p><span><strong class="command"></strong></span></p>
9085                     </td>
9086 <td>
9087                       <p>
9088                         Queries resulted in referral answer.
9089                         This corresponds to the
9090                         <span><strong class="command">referral</strong></span> counter
9091                         of previous versions of
9092                         <acronym class="acronym">BIND</acronym> 9.
9093                       </p>
9094                     </td>
9095 </tr>
9096 <tr>
9097 <td>
9098                       <p><span><strong class="command">QryNxrrset</strong></span></p>
9099                     </td>
9100 <td>
9101                       <p><span><strong class="command"></strong></span></p>
9102                     </td>
9103 <td>
9104                       <p>
9105                         Queries resulted in NOERROR responses with no data.
9106                         This corresponds to the
9107                         <span><strong class="command">nxrrset</strong></span> counter
9108                         of previous versions of
9109                         <acronym class="acronym">BIND</acronym> 9.
9110                       </p>
9111                     </td>
9112 </tr>
9113 <tr>
9114 <td>
9115                       <p><span><strong class="command">QrySERVFAIL</strong></span></p>
9116                     </td>
9117 <td>
9118                       <p><span><strong class="command">SFail</strong></span></p>
9119                     </td>
9120 <td>
9121                       <p>
9122                         Queries resulted in SERVFAIL.
9123                       </p>
9124                     </td>
9125 </tr>
9126 <tr>
9127 <td>
9128                       <p><span><strong class="command">QryFORMERR</strong></span></p>
9129                     </td>
9130 <td>
9131                       <p><span><strong class="command">SFErr</strong></span></p>
9132                     </td>
9133 <td>
9134                       <p>
9135                         Queries resulted in FORMERR.
9136                       </p>
9137                     </td>
9138 </tr>
9139 <tr>
9140 <td>
9141                       <p><span><strong class="command">QryNXDOMAIN</strong></span></p>
9142                     </td>
9143 <td>
9144                       <p><span><strong class="command">SNXD</strong></span></p>
9145                     </td>
9146 <td>
9147                       <p>
9148                         Queries resulted in NXDOMAIN.
9149                         This corresponds to the
9150                         <span><strong class="command">nxdomain</strong></span> counter
9151                         of previous versions of
9152                         <acronym class="acronym">BIND</acronym> 9.
9153                       </p>
9154                     </td>
9155 </tr>
9156 <tr>
9157 <td>
9158                       <p><span><strong class="command">QryRecursion</strong></span></p>
9159                     </td>
9160 <td>
9161                       <p><span><strong class="command">RFwdQ</strong></span></p>
9162                     </td>
9163 <td>
9164                       <p>
9165                         Queries which caused the server
9166                         to perform recursion in order to find the final answer.
9167                         This corresponds to the
9168                         <span><strong class="command">recursion</strong></span> counter
9169                         of previous versions of
9170                         <acronym class="acronym">BIND</acronym> 9.
9171                       </p>
9172                     </td>
9173 </tr>
9174 <tr>
9175 <td>
9176                       <p><span><strong class="command">QryDuplicate</strong></span></p>
9177                     </td>
9178 <td>
9179                       <p><span><strong class="command">RDupQ</strong></span></p>
9180                     </td>
9181 <td>
9182                       <p>
9183                         Queries which the server attempted to
9184                         recurse but discovered an existing query with the same
9185                         IP address, port, query ID, name, type and class
9186                         already being processed.
9187                         This corresponds to the
9188                         <span><strong class="command">duplicate</strong></span> counter
9189                         of previous versions of
9190                         <acronym class="acronym">BIND</acronym> 9.
9191                       </p>
9192                     </td>
9193 </tr>
9194 <tr>
9195 <td>
9196                       <p><span><strong class="command">QryDropped</strong></span></p>
9197                     </td>
9198 <td>
9199                       <p><span><strong class="command"></strong></span></p>
9200                     </td>
9201 <td>
9202                       <p>
9203                         Recursive queries for which the server
9204                         discovered an excessive number of existing
9205                         recursive queries for the same name, type and
9206                         class and were subsequently dropped.
9207                         This is the number of dropped queries due to
9208                         the reason explained with the
9209                         <span><strong class="command">clients-per-query</strong></span>
9210                         and
9211                         <span><strong class="command">max-clients-per-query</strong></span>
9212                         options
9213                         (see the description about
9214                         <a href="Bv9ARM.ch06.html#clients-per-query"><span><strong class="command">clients-per-query</strong></span></a>.)
9215                         This corresponds to the
9216                         <span><strong class="command">dropped</strong></span> counter
9217                         of previous versions of
9218                         <acronym class="acronym">BIND</acronym> 9.
9219                       </p>
9220                     </td>
9221 </tr>
9222 <tr>
9223 <td>
9224                       <p><span><strong class="command">QryFailure</strong></span></p>
9225                     </td>
9226 <td>
9227                       <p><span><strong class="command"></strong></span></p>
9228                     </td>
9229 <td>
9230                       <p>
9231                         Other query failures.
9232                         This corresponds to the
9233                         <span><strong class="command">failure</strong></span> counter
9234                         of previous versions of
9235                         <acronym class="acronym">BIND</acronym> 9.
9236                         Note: this counter is provided mainly for
9237                         backward compatibility with the previous versions.
9238                         Normally a more fine-grained counters such as
9239                         <span><strong class="command">AuthQryRej</strong></span> and
9240                         <span><strong class="command">RecQryRej</strong></span>
9241                         that would also fall into this counter are provided,
9242                         and so this counter would not be of much
9243                         interest in practice.
9244                       </p>
9245                     </td>
9246 </tr>
9247 <tr>
9248 <td>
9249                       <p><span><strong class="command">XfrReqDone</strong></span></p>
9250                     </td>
9251 <td>
9252                       <p><span><strong class="command"></strong></span></p>
9253                     </td>
9254 <td>
9255                       <p>
9256                         Requested zone transfers completed.
9257                       </p>
9258                     </td>
9259 </tr>
9260 <tr>
9261 <td>
9262                       <p><span><strong class="command">UpdateReqFwd</strong></span></p>
9263                     </td>
9264 <td>
9265                       <p><span><strong class="command"></strong></span></p>
9266                     </td>
9267 <td>
9268                       <p>
9269                         Update requests forwarded.
9270                       </p>
9271                     </td>
9272 </tr>
9273 <tr>
9274 <td>
9275                       <p><span><strong class="command">UpdateRespFwd</strong></span></p>
9276                     </td>
9277 <td>
9278                       <p><span><strong class="command"></strong></span></p>
9279                     </td>
9280 <td>
9281                       <p>
9282                         Update responses forwarded.
9283                       </p>
9284                     </td>
9285 </tr>
9286 <tr>
9287 <td>
9288                       <p><span><strong class="command">UpdateFwdFail</strong></span></p>
9289                     </td>
9290 <td>
9291                       <p><span><strong class="command"></strong></span></p>
9292                     </td>
9293 <td>
9294                       <p>
9295                         Dynamic update forward failed.
9296                       </p>
9297                     </td>
9298 </tr>
9299 <tr>
9300 <td>
9301                       <p><span><strong class="command">UpdateDone</strong></span></p>
9302                     </td>
9303 <td>
9304                       <p><span><strong class="command"></strong></span></p>
9305                     </td>
9306 <td>
9307                       <p>
9308                         Dynamic updates completed.
9309                       </p>
9310                     </td>
9311 </tr>
9312 <tr>
9313 <td>
9314                       <p><span><strong class="command">UpdateFail</strong></span></p>
9315                     </td>
9316 <td>
9317                       <p><span><strong class="command"></strong></span></p>
9318                     </td>
9319 <td>
9320                       <p>
9321                         Dynamic updates failed.
9322                       </p>
9323                     </td>
9324 </tr>
9325 <tr>
9326 <td>
9327                       <p><span><strong class="command">UpdateBadPrereq</strong></span></p>
9328                     </td>
9329 <td>
9330                       <p><span><strong class="command"></strong></span></p>
9331                     </td>
9332 <td>
9333                       <p>
9334                         Dynamic updates rejected due to prerequisite failure.
9335                       </p>
9336                     </td>
9337 </tr>
9338 </tbody>
9339 </table></div>
9340 </div>
9341 <div class="sect3" lang="en">
9342 <div class="titlepage"><div><div><h4 class="title">
9343 <a name="id2599033"></a>Zone Maintenance Statistics Counters</h4></div></div></div>
9344 <div class="informaltable"><table border="1">
9345 <colgroup>
9346 <col>
9347 <col>
9348 </colgroup>
9349 <tbody>
9350 <tr>
9351 <td>
9352                       <p>
9353                         <span class="emphasis"><em>Symbol</em></span>
9354                       </p>
9355                     </td>
9356 <td>
9357                       <p>
9358                         <span class="emphasis"><em>Description</em></span>
9359                       </p>
9360                     </td>
9361 </tr>
9362 <tr>
9363 <td>
9364                       <p><span><strong class="command">NotifyOutv4</strong></span></p>
9365                     </td>
9366 <td>
9367                       <p>
9368                         IPv4 notifies sent.
9369                       </p>
9370                     </td>
9371 </tr>
9372 <tr>
9373 <td>
9374                       <p><span><strong class="command">NotifyOutv6</strong></span></p>
9375                     </td>
9376 <td>
9377                       <p>
9378                         IPv6 notifies sent.
9379                       </p>
9380                     </td>
9381 </tr>
9382 <tr>
9383 <td>
9384                       <p><span><strong class="command">NotifyInv4</strong></span></p>
9385                     </td>
9386 <td>
9387                       <p>
9388                         IPv4 notifies received.
9389                       </p>
9390                     </td>
9391 </tr>
9392 <tr>
9393 <td>
9394                       <p><span><strong class="command">NotifyInv6</strong></span></p>
9395                     </td>
9396 <td>
9397                       <p>
9398                         IPv6 notifies received.
9399                       </p>
9400                     </td>
9401 </tr>
9402 <tr>
9403 <td>
9404                       <p><span><strong class="command">NotifyRej</strong></span></p>
9405                     </td>
9406 <td>
9407                       <p>
9408                         Incoming notifies rejected.
9409                       </p>
9410                     </td>
9411 </tr>
9412 <tr>
9413 <td>
9414                       <p><span><strong class="command">SOAOutv4</strong></span></p>
9415                     </td>
9416 <td>
9417                       <p>
9418                         IPv4 SOA queries sent.
9419                       </p>
9420                     </td>
9421 </tr>
9422 <tr>
9423 <td>
9424                       <p><span><strong class="command">SOAOutv6</strong></span></p>
9425                     </td>
9426 <td>
9427                       <p>
9428                         IPv6 SOA queries sent.
9429                       </p>
9430                     </td>
9431 </tr>
9432 <tr>
9433 <td>
9434                       <p><span><strong class="command">AXFRReqv4</strong></span></p>
9435                     </td>
9436 <td>
9437                       <p>
9438                         IPv4 AXFR requested.
9439                       </p>
9440                     </td>
9441 </tr>
9442 <tr>
9443 <td>
9444                       <p><span><strong class="command">AXFRReqv6</strong></span></p>
9445                     </td>
9446 <td>
9447                       <p>
9448                         IPv6 AXFR requested.
9449                       </p>
9450                     </td>
9451 </tr>
9452 <tr>
9453 <td>
9454                       <p><span><strong class="command">IXFRReqv4</strong></span></p>
9455                     </td>
9456 <td>
9457                       <p>
9458                         IPv4 IXFR requested.
9459                       </p>
9460                     </td>
9461 </tr>
9462 <tr>
9463 <td>
9464                       <p><span><strong class="command">IXFRReqv6</strong></span></p>
9465                     </td>
9466 <td>
9467                       <p>
9468                         IPv6 IXFR requested.
9469                       </p>
9470                     </td>
9471 </tr>
9472 <tr>
9473 <td>
9474                       <p><span><strong class="command">XfrSuccess</strong></span></p>
9475                     </td>
9476 <td>
9477                       <p>
9478                         Zone transfer requests succeeded.
9479                       </p>
9480                     </td>
9481 </tr>
9482 <tr>
9483 <td>
9484                       <p><span><strong class="command">XfrFail</strong></span></p>
9485                     </td>
9486 <td>
9487                       <p>
9488                         Zone transfer requests failed.
9489                       </p>
9490                     </td>
9491 </tr>
9492 </tbody>
9493 </table></div>
9494 </div>
9495 <div class="sect3" lang="en">
9496 <div class="titlepage"><div><div><h4 class="title">
9497 <a name="id2599484"></a>Resolver Statistics Counters</h4></div></div></div>
9498 <div class="informaltable"><table border="1">
9499 <colgroup>
9500 <col>
9501 <col>
9502 <col>
9503 </colgroup>
9504 <tbody>
9505 <tr>
9506 <td>
9507                       <p>
9508                         <span class="emphasis"><em>Symbol</em></span>
9509                       </p>
9510                     </td>
9511 <td>
9512                       <p>
9513                         <span class="emphasis"><em>BIND8 Symbol</em></span>
9514                       </p>
9515                     </td>
9516 <td>
9517                       <p>
9518                         <span class="emphasis"><em>Description</em></span>
9519                       </p>
9520                     </td>
9521 </tr>
9522 <tr>
9523 <td>
9524                       <p><span><strong class="command">Queryv4</strong></span></p>
9525                     </td>
9526 <td>
9527                       <p><span><strong class="command">SFwdQ</strong></span></p>
9528                     </td>
9529 <td>
9530                       <p>
9531                         IPv4 queries sent.
9532                       </p>
9533                     </td>
9534 </tr>
9535 <tr>
9536 <td>
9537                       <p><span><strong class="command">Queryv6</strong></span></p>
9538                     </td>
9539 <td>
9540                       <p><span><strong class="command">SFwdQ</strong></span></p>
9541                     </td>
9542 <td>
9543                       <p>
9544                         IPv6 queries sent.
9545                       </p>
9546                     </td>
9547 </tr>
9548 <tr>
9549 <td>
9550                       <p><span><strong class="command">Responsev4</strong></span></p>
9551                     </td>
9552 <td>
9553                       <p><span><strong class="command">RR</strong></span></p>
9554                     </td>
9555 <td>
9556                       <p>
9557                         IPv4 responses received.
9558                       </p>
9559                     </td>
9560 </tr>
9561 <tr>
9562 <td>
9563                       <p><span><strong class="command">Responsev6</strong></span></p>
9564                     </td>
9565 <td>
9566                       <p><span><strong class="command">RR</strong></span></p>
9567                     </td>
9568 <td>
9569                       <p>
9570                         IPv6 responses received.
9571                       </p>
9572                     </td>
9573 </tr>
9574 <tr>
9575 <td>
9576                       <p><span><strong class="command">NXDOMAIN</strong></span></p>
9577                     </td>
9578 <td>
9579                       <p><span><strong class="command">RNXD</strong></span></p>
9580                     </td>
9581 <td>
9582                       <p>
9583                         NXDOMAIN received.
9584                       </p>
9585                     </td>
9586 </tr>
9587 <tr>
9588 <td>
9589                       <p><span><strong class="command">SERVFAIL</strong></span></p>
9590                     </td>
9591 <td>
9592                       <p><span><strong class="command">RFail</strong></span></p>
9593                     </td>
9594 <td>
9595                       <p>
9596                         SERVFAIL received.
9597                       </p>
9598                     </td>
9599 </tr>
9600 <tr>
9601 <td>
9602                       <p><span><strong class="command">FORMERR</strong></span></p>
9603                     </td>
9604 <td>
9605                       <p><span><strong class="command">RFErr</strong></span></p>
9606                     </td>
9607 <td>
9608                       <p>
9609                         FORMERR received.
9610                       </p>
9611                     </td>
9612 </tr>
9613 <tr>
9614 <td>
9615                       <p><span><strong class="command">OtherError</strong></span></p>
9616                     </td>
9617 <td>
9618                       <p><span><strong class="command">RErr</strong></span></p>
9619                     </td>
9620 <td>
9621                       <p>
9622                         Other errors received.
9623                       </p>
9624                     </td>
9625 </tr>
9626 <tr>
9627 <td>
9628                       <p><span><strong class="command">EDNS0Fail</strong></span></p>
9629                                                  </td>
9630 <td>
9631                       <p><span><strong class="command"></strong></span></p>
9632                     </td>
9633 <td>
9634                       <p>
9635                         EDNS(0) query failures.
9636                       </p>
9637                     </td>
9638 </tr>
9639 <tr>
9640 <td>
9641                       <p><span><strong class="command">Mismatch</strong></span></p>
9642                     </td>
9643 <td>
9644                       <p><span><strong class="command">RDupR</strong></span></p>
9645                     </td>
9646 <td>
9647                       <p>
9648                         Mismatch responses received.
9649                         The DNS ID, response's source address,
9650                         and/or the response's source port does not
9651                         match what was expected.
9652                         (The port must be 53 or as defined by
9653                         the <span><strong class="command">port</strong></span> option.)
9654                         This may be an indication of a cache
9655                         poisoning attempt.
9656                       </p>
9657                     </td>
9658 </tr>
9659 <tr>
9660 <td>
9661                       <p><span><strong class="command">Truncated</strong></span></p>
9662                     </td>
9663 <td>
9664                       <p><span><strong class="command"></strong></span></p>
9665                     </td>
9666 <td>
9667                       <p>
9668                         Truncated responses received.
9669                       </p>
9670                     </td>
9671 </tr>
9672 <tr>
9673 <td>
9674                       <p><span><strong class="command">Lame</strong></span></p>
9675                     </td>
9676 <td>
9677                       <p><span><strong class="command">RLame</strong></span></p>
9678                     </td>
9679 <td>
9680                       <p>
9681                         Lame delegations received.
9682                       </p>
9683                     </td>
9684 </tr>
9685 <tr>
9686 <td>
9687                       <p><span><strong class="command">Retry</strong></span></p>
9688                     </td>
9689 <td>
9690                       <p><span><strong class="command">SDupQ</strong></span></p>
9691                     </td>
9692 <td>
9693                       <p>
9694                         Query retries performed.
9695                       </p>
9696                     </td>
9697 </tr>
9698 <tr>
9699 <td>
9700                       <p><span><strong class="command">QueryAbort</strong></span></p>
9701                     </td>
9702 <td>
9703                       <p><span><strong class="command"></strong></span></p>
9704                     </td>
9705 <td>
9706                       <p>
9707                         Queries aborted due to quota control.
9708                       </p>
9709                     </td>
9710 </tr>
9711 <tr>
9712 <td>
9713                       <p><span><strong class="command">QuerySockFail</strong></span></p>
9714                     </td>
9715 <td>
9716                       <p><span><strong class="command"></strong></span></p>
9717                     </td>
9718 <td>
9719                       <p>
9720                         Failures in opening query sockets.
9721                         One common reason for such failures is a
9722                         failure of opening a new socket due to a
9723                         limitation on file descriptors.
9724                       </p>
9725                     </td>
9726 </tr>
9727 <tr>
9728 <td>
9729                       <p><span><strong class="command">QueryTimeout</strong></span></p>
9730                     </td>
9731 <td>
9732                       <p><span><strong class="command"></strong></span></p>
9733                     </td>
9734 <td>
9735                       <p>
9736                         Query timeouts.
9737                       </p>
9738                     </td>
9739 </tr>
9740 <tr>
9741 <td>
9742                       <p><span><strong class="command">GlueFetchv4</strong></span></p>
9743                     </td>
9744 <td>
9745                       <p><span><strong class="command">SSysQ</strong></span></p>
9746                     </td>
9747 <td>
9748                       <p>
9749                         IPv4 NS address fetches invoked.
9750                       </p>
9751                     </td>
9752 </tr>
9753 <tr>
9754 <td>
9755                       <p><span><strong class="command">GlueFetchv6</strong></span></p>
9756                     </td>
9757 <td>
9758                       <p><span><strong class="command">SSysQ</strong></span></p>
9759                     </td>
9760 <td>
9761                       <p>
9762                         IPv6 NS address fetches invoked.
9763                       </p>
9764                     </td>
9765 </tr>
9766 <tr>
9767 <td>
9768                       <p><span><strong class="command">GlueFetchv4Fail</strong></span></p>
9769                     </td>
9770 <td>
9771                       <p><span><strong class="command"></strong></span></p>
9772                     </td>
9773 <td>
9774                       <p>
9775                         IPv4 NS address fetch failed.
9776                       </p>
9777                     </td>
9778 </tr>
9779 <tr>
9780 <td>
9781                       <p><span><strong class="command">GlueFetchv6Fail</strong></span></p>
9782                     </td>
9783 <td>
9784                       <p><span><strong class="command"></strong></span></p>
9785                     </td>
9786 <td>
9787                       <p>
9788                         IPv6 NS address fetch failed.
9789                       </p>
9790                     </td>
9791 </tr>
9792 <tr>
9793 <td>
9794                       <p><span><strong class="command">ValAttempt</strong></span></p>
9795                     </td>
9796 <td>
9797                       <p><span><strong class="command"></strong></span></p>
9798                     </td>
9799 <td>
9800                       <p>
9801                         DNSSEC validation attempted.
9802                       </p>
9803                     </td>
9804 </tr>
9805 <tr>
9806 <td>
9807                       <p><span><strong class="command">ValOk</strong></span></p>
9808                     </td>
9809 <td>
9810                       <p><span><strong class="command"></strong></span></p>
9811                     </td>
9812 <td>
9813                       <p>
9814                         DNSSEC validation succeeded.
9815                       </p>
9816                     </td>
9817 </tr>
9818 <tr>
9819 <td>
9820                       <p><span><strong class="command">ValNegOk</strong></span></p>
9821                     </td>
9822 <td>
9823                       <p><span><strong class="command"></strong></span></p>
9824                     </td>
9825 <td>
9826                       <p>
9827                         DNSSEC validation on negative information succeeded.
9828                       </p>
9829                     </td>
9830 </tr>
9831 <tr>
9832 <td>
9833                       <p><span><strong class="command">ValFail</strong></span></p>
9834                     </td>
9835 <td>
9836                       <p><span><strong class="command"></strong></span></p>
9837                     </td>
9838 <td>
9839                       <p>
9840                         DNSSEC validation failed.
9841                       </p>
9842                     </td>
9843 </tr>
9844 <tr>
9845 <td>
9846                       <p><span><strong class="command">QryRTTnn</strong></span></p>
9847                     </td>
9848 <td>
9849                       <p><span><strong class="command"></strong></span></p>
9850                     </td>
9851 <td>
9852                       <p>
9853                         Frequency table on round trip times (RTTs) of
9854                         queries.
9855                         Each <span><strong class="command">nn</strong></span> specifies the corresponding
9856                         frequency.
9857                         In the sequence of
9858                         <span><strong class="command">nn_1</strong></span>,
9859                         <span><strong class="command">nn_2</strong></span>,
9860                         ...,
9861                         <span><strong class="command">nn_m</strong></span>,
9862                         the value of <span><strong class="command">nn_i</strong></span> is the
9863                         number of queries whose RTTs are between
9864                         <span><strong class="command">nn_(i-1)</strong></span> (inclusive) and
9865                         <span><strong class="command">nn_i</strong></span> (exclusive) milliseconds.
9866                         For the sake of convenience we define
9867                         <span><strong class="command">nn_0</strong></span> to be 0.
9868                         The last entry should be represented as
9869                         <span><strong class="command">nn_m+</strong></span>, which means the
9870                         number of queries whose RTTs are equal to or over
9871                         <span><strong class="command">nn_m</strong></span> milliseconds.
9872                       </p>
9873                     </td>
9874 </tr>
9875 </tbody>
9876 </table></div>
9877 </div>
9878 <div class="sect3" lang="en">
9879 <div class="titlepage"><div><div><h4 class="title">
9880 <a name="id2600506"></a>Socket I/O Statistics Counters</h4></div></div></div>
9881 <p>
9882               Socket I/O statistics counters are defined per socket
9883               types, which are
9884               <span><strong class="command">UDP4</strong></span> (UDP/IPv4),
9885               <span><strong class="command">UDP6</strong></span> (UDP/IPv6),
9886               <span><strong class="command">TCP4</strong></span> (TCP/IPv4),
9887               <span><strong class="command">TCP6</strong></span> (TCP/IPv6),
9888               <span><strong class="command">Unix</strong></span> (Unix Domain), and
9889               <span><strong class="command">FDwatch</strong></span> (sockets opened outside the
9890               socket module).
9891               In the following table <span><strong class="command">&lt;TYPE&gt;</strong></span>
9892               represents a socket type.
9893               Not all counters are available for all socket types;
9894               exceptions are noted in the description field.
9895             </p>
9896 <div class="informaltable"><table border="1">
9897 <colgroup>
9898 <col>
9899 <col>
9900 </colgroup>
9901 <tbody>
9902 <tr>
9903 <td>
9904                       <p>
9905                         <span class="emphasis"><em>Symbol</em></span>
9906                       </p>
9907                     </td>
9908 <td>
9909                       <p>
9910                         <span class="emphasis"><em>Description</em></span>
9911                       </p>
9912                     </td>
9913 </tr>
9914 <tr>
9915 <td>
9916                       <p><span><strong class="command">&lt;TYPE&gt;Open</strong></span></p>
9917                     </td>
9918 <td>
9919                       <p>
9920                         Sockets opened successfully.
9921                         This counter is not applicable to the
9922                         <span><strong class="command">FDwatch</strong></span> type.
9923                       </p>
9924                     </td>
9925 </tr>
9926 <tr>
9927 <td>
9928                       <p><span><strong class="command">&lt;TYPE&gt;OpenFail</strong></span></p>
9929                     </td>
9930 <td>
9931                       <p>
9932                         Failures of opening sockets.
9933                         This counter is not applicable to the
9934                         <span><strong class="command">FDwatch</strong></span> type.
9935                       </p>
9936                     </td>
9937 </tr>
9938 <tr>
9939 <td>
9940                       <p><span><strong class="command">&lt;TYPE&gt;Close</strong></span></p>
9941                     </td>
9942 <td>
9943                       <p>
9944                         Sockets closed.
9945                       </p>
9946                     </td>
9947 </tr>
9948 <tr>
9949 <td>
9950                       <p><span><strong class="command">&lt;TYPE&gt;BindFail</strong></span></p>
9951                     </td>
9952 <td>
9953                       <p>
9954                         Failures of binding sockets.
9955                       </p>
9956                     </td>
9957 </tr>
9958 <tr>
9959 <td>
9960                       <p><span><strong class="command">&lt;TYPE&gt;ConnFail</strong></span></p>
9961                     </td>
9962 <td>
9963                       <p>
9964                         Failures of connecting sockets.
9965                       </p>
9966                     </td>
9967 </tr>
9968 <tr>
9969 <td>
9970                       <p><span><strong class="command">&lt;TYPE&gt;Conn</strong></span></p>
9971                     </td>
9972 <td>
9973                       <p>
9974                         Connections established successfully.
9975                       </p>
9976                     </td>
9977 </tr>
9978 <tr>
9979 <td>
9980                       <p><span><strong class="command">&lt;TYPE&gt;AcceptFail</strong></span></p>
9981                     </td>
9982 <td>
9983                       <p>
9984                         Failures of accepting incoming connection requests.
9985                         This counter is not applicable to the
9986                         <span><strong class="command">UDP</strong></span> and
9987                         <span><strong class="command">FDwatch</strong></span> types.
9988                       </p>
9989                     </td>
9990 </tr>
9991 <tr>
9992 <td>
9993                       <p><span><strong class="command">&lt;TYPE&gt;Accept</strong></span></p>
9994                     </td>
9995 <td>
9996                       <p>
9997                         Incoming connections successfully accepted.
9998                         This counter is not applicable to the
9999                         <span><strong class="command">UDP</strong></span> and
10000                         <span><strong class="command">FDwatch</strong></span> types.
10001                       </p>
10002                     </td>
10003 </tr>
10004 <tr>
10005 <td>
10006                       <p><span><strong class="command">&lt;TYPE&gt;SendErr</strong></span></p>
10007                     </td>
10008 <td>
10009                       <p>
10010                         Errors in socket send operations.
10011                         This counter corresponds
10012                         to <span><strong class="command">SErr</strong></span> counter of
10013                         <span><strong class="command">BIND</strong></span> 8.
10014                       </p>
10015                     </td>
10016 </tr>
10017 <tr>
10018 <td>
10019                       <p><span><strong class="command">&lt;TYPE&gt;RecvErr</strong></span></p>
10020                     </td>
10021 <td>
10022                       <p>
10023                         Errors in socket receive operations.
10024                         This includes errors of send operations on a
10025                         connected UDP socket notified by an ICMP error
10026                         message.
10027                       </p>
10028                     </td>
10029 </tr>
10030 </tbody>
10031 </table></div>
10032 </div>
10033 <div class="sect3" lang="en">
10034 <div class="titlepage"><div><div><h4 class="title">
10035 <a name="id2600948"></a>Compatibility with <span class="emphasis"><em>BIND</em></span> 8 Counters</h4></div></div></div>
10036 <p>
10037               Most statistics counters that were available
10038               in <span><strong class="command">BIND</strong></span> 8 are also supported in
10039               <span><strong class="command">BIND</strong></span> 9 as shown in the above tables.
10040               Here are notes about other counters that do not appear
10041               in these tables.
10042             </p>
10043 <div class="variablelist"><dl>
10044 <dt><span class="term"><span><strong class="command">RFwdR,SFwdR</strong></span></span></dt>
10045 <dd><p>
10046                     These counters are not supported
10047                     because <span><strong class="command">BIND</strong></span> 9 does not adopt
10048                     the notion of <span class="emphasis"><em>forwarding</em></span>
10049                     as <span><strong class="command">BIND</strong></span> 8 did.
10050                   </p></dd>
10051 <dt><span class="term"><span><strong class="command">RAXFR</strong></span></span></dt>
10052 <dd><p>
10053                     This counter is accessible in the Incoming Queries section.
10054                   </p></dd>
10055 <dt><span class="term"><span><strong class="command">RIQ</strong></span></span></dt>
10056 <dd><p>
10057                     This counter is accessible in the Incoming Requests section.
10058                   </p></dd>
10059 <dt><span class="term"><span><strong class="command">ROpts</strong></span></span></dt>
10060 <dd><p>
10061                     This counter is not supported
10062                     because <span><strong class="command">BIND</strong></span> 9 does not care
10063                     about IP options in the first place.
10064                   </p></dd>
10065 </dl></div>
10066 </div>
10067 </div>
10068 </div>
10069 </div>
10070 <div class="navfooter">
10071 <hr>
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10073 <tr>
10074 <td width="40%" align="left">
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10078 </td>
10079 </tr>
10080 <tr>
10081 <td width="40%" align="left" valign="top">Chapter 5. The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver </td>
10082 <td width="20%" align="center"><a accesskey="h" href="Bv9ARM.html">Home</a></td>
10083 <td width="40%" align="right" valign="top"> Chapter 7. <acronym class="acronym">BIND</acronym> 9 Security Considerations</td>
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