4 tethereal - Dump and analyze network traffic
9 S<[ B<-a> capture autostop condition ] ...>
10 S<[ B<-b> number of ring buffer files ]>
13 S<[ B<-f> capture filter expression ]>
14 S<[ B<-F> file format ]>
16 S<[ B<-i> interface ]>
19 S<[ B<-N> resolving flags ]>
20 S<[ B<-o> preference setting ] ...>
24 S<[ B<-R> display filter expression ]>
27 S<[ B<-t> time stamp format ]>
32 S<[ B<-z> statistics-string ]>
33 S<[ filter expression ]>
37 B<Tethereal> is a network protocol analyzer. It lets you capture packet
38 data from a live network, or read packets from a previously saved
39 capture file, either printing a decoded form of those packets to the
40 standard output or writing the packets to a file. B<Tethereal>'s native
41 capture file format is B<libpcap> format, which is also the format used
42 by B<tcpdump> and various other tools. In addition, B<Tethereal> can
43 read capture files from B<snoop> and B<atmsnoop>, Shomiti/Finisar
44 B<Surveyor>, Novell B<LANalyzer>, Network General/Network Associates
45 DOS-based B<Sniffer> (compressed or uncompressed), Microsoft B<Network
46 Monitor>, AIX's B<iptrace>, Cinco Networks B<NetXRay>, Network
47 Associates Windows-based B<Sniffer>, AG Group/WildPackets
48 B<EtherPeek>/B<TokenPeek>/B<AiroPeek>, B<RADCOM>'s WAN/LAN analyzer,
49 B<Lucent/Ascend> router debug output, HP-UX's B<nettl>, the dump output
50 from B<Toshiba's> ISDN routers, the output from B<i4btrace> from the
51 ISDN4BSD project, the output in B<IPLog> format from the Cisco Secure
52 Intrusion Detection System, B<pppd logs> (pppdump format), the output
53 from VMS's B<TCPIPtrace> utility, the text output from the B<DBS
54 Etherwatch> VMS utility, traffic capture files from Visual Networks'
55 Visual UpTime, and the output from B<CoSine> L2 debug. There is no
56 need to tell B<Tethereal> what type of file you are reading; it will
57 determine the file type by itself. B<Tethereal> is also capable of
58 reading any of these file formats if they are compressed using gzip.
59 B<Tethereal> recognizes this directly from the file; the '.gz' extension
60 is not required for this purpose.
62 If the B<-w> flag is not specified, B<Tethereal> prints a decoded form
63 of the packets it captures or reads; otherwise, it writes those packets
64 to the file specified by that flag.
66 When printing a decoded form of packets, B<Tethereal> prints, by
67 default, a summary line containing the fields specified by the
68 preferences file (which are also the fields displayed in the packet list
69 pane in B<Ethereal>), although if it's printing packets as it captures
70 them, rather than printing packets from a saved capture file, it won't
71 print the "frame number" field. If the B<-V> flag is specified, it
72 prints intead a protocol tree, showing all the fields of all protocols
75 When writing packets to a file, B<Tethereal>, by default, writes the
76 file in B<libpcap> format, and writes all of the packets it sees to the
77 output file. The B<-F> flag can be used to specify the format in which
78 to write the file; it can write the file in B<libpcap> format (standard
79 B<libpcap> format, a modified format used by some patched versions of
80 B<libpcap>, or the format used by Red Hat Linux 6.1), B<snoop> format,
81 uncompressed B<Sniffer> format, Microsoft B<Network Monitor> 1.x format,
82 the format used by Windows-based versions of the B<Sniffer>
83 software, and the format used by Visual Networks' software.
85 Read filters in B<Tethereal>, which allow you to select which packets
86 are to be decoded or written to a file, are very powerful; more fields
87 are filterable in B<Tethereal> than in other protocol analyzers, and the
88 syntax you can use to create your filters is richer. As B<Tethereal>
89 progresses, expect more and more protocol fields to be allowed in read
92 Packet capturing is performed with the pcap library. The capture filter
93 syntax follows the rules of the pcap library. This syntax is different
94 from the read filter syntax. A read filter can also be specified when
95 capturing, and only packets that pass the read filter will be displayed
96 or saved to the output file; note, however, that capture filters are much
97 more efficient than read filters, and it may be more difficult for
98 B<Tethereal> to keep up with a busy network if a read filter is
99 specified for a live capture.
101 Compressed file support uses (and therefore requires) the zlib library.
102 If the zlib library is not present, B<Tethereal> will compile, but will
103 be unable to read compressed files.
105 A capture or read filter can either be specified with the B<-f> or B<-R>
106 option, respectively, in which case the entire filter expression must be
107 specified as a single argument (which means that if it contains spaces,
108 it must be quoted), or can be specified with command-line arguments
109 after the option arguments, in which case all the arguments after the
110 filter arguments are treated as a filter expression. If the filter is
111 specified with command-line arguments after the option arguments, it's a
112 capture filter if a capture is being done (i.e., if no B<-r> flag was
113 specified) and a read filter if a capture file is being read (i.e., if a
114 B<-r> flag was specified).
122 Specify a criterion that specifies when B<Tethereal> is to stop writing
123 to a capture file. The criterion is of the form I<test>B<:>I<value>,
124 where I<test> is one of:
132 Stop writing to a capture file after I<value> seconds have elapsed.
136 Stop writing to a capture file after it reaches a size of I<value>
137 kilobytes (where a kilobyte is 1000 bytes, not 1024 bytes).
145 If a maximum capture file size was specified, cause B<Tethereal> to run
146 in "ring buffer" mode, with the specified number of files. In "ring
147 buffer" mode, B<Tethereal> will write to several capture files; the name
148 of the first file, while the capture is in progress, will be the name
149 specified by the B<-w> flag, and subsequent files with have .I<n>
150 appended, with I<n> counting up.
152 When the first capture file fills up, B<Tethereal> will switch to
153 writing to the next file, until it fills up the last file, at which
154 point it'll discard the data in the first file and start writing to that
155 file. When that file fills up, B<Tethereal> will discard the data in
156 the next file and start writing to it, and so on.
158 When the capture completes, the files will be renamed to have names
159 based on the number of the file and on the date and time at which
160 packets most recently started being written to the file.
162 You can only save files in B<libpcap> format when using a ring buffer.
166 Set the default number of packets to read when capturing live
171 Print a list of the interfaces on which B<Tethereal> can capture, and
172 exit. Note that "can capture" means that B<Tethereal> was able to open
173 that device to do a live capture; if, on your system, a program doing a
174 network capture must be run from an account with special privileges (for
175 example, as root), then, if B<Tethereal> is run with the B<-D> flag and
176 is not run from such an account, it will not list any interfaces.
180 Set the capture filter expression.
184 Set the file format of the output capture file.
188 Print the version and options and exits.
192 Set the name of the network interface to use for live packet capture. It
193 should match one of the names listed in "B<tethereal -D>" (described
194 above). If you're using Unix, "B<netstat -i>" or "B<ifconfig -a>" should
195 also work. If no interface is specified, B<Tethereal> searches the list
196 of interfaces, choosing the first non-loopback interface if there are any
197 non-loopback interfaces, and choosing the first loopback interface if
198 there are no non-loopback interfaces; if there are no interfaces,
199 B<Tethereal> reports an error and doesn't start the capture.
203 Flush the standard output after the information for each packet is
204 printed. (This is not, strictly speaking, line-buffered if B<-V>
205 was specified; however, it is the same as line-buffered if B<-V> wasn't
206 specified, as only one line is printed for each packet, and, as B<-l> is
207 normally used when piping a live capture to a program or script, so that
208 output for a packet shows up as soon as the packet is seen and
209 dissected, it should work just as well as true line-buffering. We do
210 this as a workaround for a deficiency in the Microsoft Visual C++ C
213 This may be useful when piping the output of B<Tethereal> to another
214 program, as it means that the program to which the output is piped will
215 see the dissected data for a packet as soon as B<Tethereal> sees the
216 packet and generates that output, rather than seeing it only when the
217 standard output buffer containing that data fills up.
221 Disable network object name resolution (such as hostname, TCP and UDP port
226 Turn on name resolving for particular types of addresses and port
227 numbers, with name resolving for other types of addresses and port
228 numbers turned off; the argument is a string that may contain the
229 letters B<m> to enable MAC address resolution, B<n> to enable network
230 address resolution, and B<t> to enable transport-layer port number
231 resolution. This overrides B<-n> if both B<-N> and B<-n> are present.
235 Set a preference value, overriding the default value and any value read
236 from a preference file. The argument to the flag is a string of the
237 form I<prefname>B<:>I<value>, where I<prefname> is the name of the
238 preference (which is the same name that would appear in the preference
239 file), and I<value> is the value to which it should be set.
243 I<Don't> put the interface into promiscuous mode. Note that the
244 interface might be in promiscuous mode for some other reason; hence,
245 B<-p> cannot be used to ensure that the only traffic that is captured is
246 traffic sent to or from the machine on which B<Tethereal> is running,
247 broadcast traffic, and multicast traffic to addresses received by that
252 Don't display the continuous count of packets captured that is normally
253 shown when saving a capture to a file; instead, just display, at the end
254 of the capture, a count of packets captured.
258 Read packet data from I<infile>.
262 Cause the specified filter (which uses the syntax of read filters,
263 rather than that of capture filters) to be applied before printing a
264 decoded form of packets or writing packets to a file; packets not
265 matching the filter are discarded rather than being printed or written.
269 Set the default snapshot length to use when capturing live data.
270 No more than I<snaplen> bytes of each network packet will be read into
271 memory, or saved to disk.
275 Decode and display packets even while writing to file.
279 Set the format of the packet timestamp printed in summary lines. The
280 format can be one of 'r' (relative), 'a' (absolute), 'ad' (absolute with
281 date), or 'd' (delta). The relative time is the time elapsed between
282 the first packet and the current packet. The absolute time is the
283 actual time the packet was captured, with no date displayed; the
284 absolute date and time is the actual time and date the packet was
285 captured. The delta time is the time since the previous packet was
286 captured. The default is relative.
290 Print the version and exit.
294 Cause B<Tethereal> to print a protocol tree for each packet rather than
295 a one-line summary of the packet.
299 Write packet data to I<savefile> or to the standard output if
304 Cause B<Tethereal> to print a hex and ASCII dump of the packet data
305 after printing the summary or protocol tree.
309 Get B<Tethereal> to collect various types of statistics and display the result
310 after finishing reading the capture file.
311 Currently implemented statistics are:
313 B<-z> dcerpc,rtt,I<uuid>,I<major>.I<minor>[,I<filter>]
315 Collect call/reply RTT data for DCERPC interface I<uuid>,
316 version I<major>.I<minor>.
317 Data collected is number of calls for each procedure, MinRTT, MaxRTT
319 Example: use B<-z dcerpc,rtt,12345778-1234-abcd-ef00-0123456789ac,1.0> to collect data for CIFS SAMR Interface.
320 This option can be used multiple times on the command line.
322 If the optional filterstring is provided, the stats will only be calculated
323 on those calls that match that filter.
324 Example: use B<-z dcerpc,rtt,12345778-1234-abcd-ef00-0123456789ac,1.0,ip.addr==1.2.3.4> to collect SAMR
325 RTT statistics for a specific host.
328 B<-z> io,phs[,I<filter>]
330 Create Protocol Hierarchy Statistics listing both number of frames and bytes.
331 If no I<filter> is specified the statistics will be calculated for all frames.
332 If a I<filters> is specified statistics will be only calculated for those
333 packets that match the filter.
335 This option can be used multiple times on the command line.
338 B<-z> io,stat,I<interval>[,I<filter>][,I<filter>][,I<filter>]...
340 Collect frame/bytes statistics for the capture in intervals of I<interval>
342 If no I<filter> is specified the statistics will be calculated for all frames.
343 If one or more I<filters> are specified statistics will be calculated for
344 all filters and presented with one column of statistics for each filter.
346 This option can be used multiple times on the command line.
349 B<-z> rpc,rtt,I<program>,I<version>[,I<filter>]
351 Collect call/reply RTT data for I<program>/I<version>. Data collected
352 is number of calls for each procedure, MinRTT, MaxRTT and AvgRTT.
353 Example: use B<-z rpc,rtt,100003,3> to collect data for NFS v3. This
354 option can be used multiple times on the command line.
356 If the optional filterstring is provided, the stats will only be calculated
357 on those calls that match that filter.
358 Example: use B<-z rpc,rtt,100003,3,nfs.fh.hash==0x12345678> to collect NFS v3
359 RTT statistics for a specific file.
364 Collect call/reply RTT data for all known ONC-RPC programs/versions.
365 Data collected is number of calls for each protocol/version, MinRTT,
367 This option can only be used once on the command line.
372 =head1 CAPTURE FILTER SYNTAX
374 See manual page of tcpdump(8).
376 =head1 READ FILTER SYNTAX
378 Read filters help you remove the noise from a packet trace and let you
379 see only the packets that interest you. If a packet meets the
380 requirements expressed in your read filter, then it is printed. Read
381 filters let you compare the fields within a protocol against a specific
382 value, compare fields against fields, and to check the existence of
383 specified fields or protocols.
385 The simplest read filter allows you to check for the existence of a
386 protocol or field. If you want to see all packets which contain the IPX
387 protocol, the filter would be "ipx". (Without the quotation marks) To
388 see all packets that contain a Token-Ring RIF field, use "tr.rif".
390 Fields can also be compared against values. The comparison operators
391 can be expressed either through C-like symbols, or through English-like
398 ge, >= Greater than or Equal to
399 le, <= Less than or Equal to
401 Furthermore, each protocol field is typed. The types are:
403 Unsigned integer (either 8-bit, 16-bit, 24-bit, or 32-bit)
404 Signed integer (either 8-bit, 16-bit, 24-bit, or 32-bit)
406 Ethernet address (6 bytes)
407 Byte string (n-number of bytes)
412 Double-precision floating point number
414 An integer may be expressed in decimal, octal, or hexadecimal notation.
415 The following three read filters are equivalent:
421 Boolean values are either true or false. In a read filter expression
422 testing the value of a Boolean field, "true" is expressed as 1 or any
423 other non-zero value, and "false" is expressed as zero. For example, a
424 token-ring packet's source route field is boolean. To find any
425 source-routed packets, a read filter would be:
429 Non source-routed packets can be found with:
433 Ethernet addresses, as well as a string of bytes, are represented in hex
434 digits. The hex digits may be separated by colons, periods, or hyphens:
436 fddi.dst eq ff:ff:ff:ff:ff:ff
437 ipx.srcnode == 0.0.0.0.0.1
438 eth.src == aa-aa-aa-aa-aa-aa
440 If a string of bytes contains only one byte, then it is represented as
441 an unsigned integer. That is, if you are testing for hex value 'ff' in
442 a one-byte byte-string, you must compare it agains '0xff' and not 'ff'.
444 IPv4 addresses can be represented in either dotted decimal notation, or
445 by using the hostname:
447 ip.dst eq www.mit.edu
448 ip.src == 192.168.1.1
450 IPv4 addresses can be compared with the same logical relations as numbers:
451 eq, ne, gt, ge, lt, and le. The IPv4 address is stored in host order,
452 so you do not have to worry about how the endianness of an IPv4 address
453 when using it in a read filter.
455 Classless InterDomain Routing (CIDR) notation can be used to test if an
456 IPv4 address is in a certain subnet. For example, this display filter
457 will find all packets in the 129.111 Class-B network:
459 ip.addr == 129.111.0.0/16
461 Remember, the number after the slash represents the number of bits used
462 to represent the network. CIDR notation can also be used with
463 hostnames, in this example of finding IP addresses on the same Class C
468 The CIDR notation can only be used on IP addresses or hostnames, not in
469 variable names. So, a display filter like "ip.src/24 == ip.dst/24" is
472 IPX networks are represented by unsigned 32-bit integers. Most likely
473 you will be using hexadecimal when testing for IPX network values:
475 ipx.srcnet == 0xc0a82c00
477 A slice operator also exists. You can check the substring
478 (byte-string) of any protocol or field. For example, you can filter on
479 the vendor portion of an ethernet address (the first three bytes) like
482 eth.src[0:3] == 00:00:83
484 If the length of your byte-slice is only one byte, then it is still
485 represented in hex, but without the preceding "0x":
489 You can use the slice operator on a protocol name, too. And
490 remember, the "frame" protocol encompasses the entire packet, allowing
491 you to look at the nth byte of a packet regardless of its frame type
492 (Ethernet, token-ring, etc.).
494 token[0:5] ne 0.0.0.1.1
498 The following syntax governs slices:
500 [i:j] i = start_offset, j = length
501 [i-j] i = start_offet, j = end_offset, inclusive.
502 [i] i = start_offset, length = 1
503 [:j] start_offset = 0, length = j
504 [i:] start_offset = i, end_offset = end_of_field
506 Offsets and lengths can be negative, in which case they indicate the
507 offset from the B<end> of the field. Here's how to check the last 4
510 frame[-4:4] == 0.1.2.3
514 frame[-4:] == 0.1.2.3
516 You can create complex concatenations of slices using the comma operator:
518 field[1,3-5,9:] == 01:03:04:05:09:0a:0b
520 All the above tests can be combined together with logical expressions.
521 These too are expressable in C-like syntax or with English-like
528 Expressions can be grouped by parentheses as well. The following are
529 all valid read filter expression:
531 tcp.port == 80 and ip.src == 192.168.2.1
533 (ipx.srcnet == 0xbad && ipx.srnode == 0.0.0.0.0.1) || ip
534 tr.dst[0:3] == 0.6.29 xor tr.src[0:3] == 0.6.29
536 A special caveat must be given regarding fields that occur more than
537 once per packet. "ip.addr" occurs twice per IP packet, once for the
538 source address, and once for the destination address. Likewise,
539 tr.rif.ring fields can occur more than once per packet. The following
540 two expressions are not equivalent:
542 ip.addr ne 192.168.4.1
543 not ip.addr eq 192.168.4.1
545 The first filter says "show me IP packets where an ip.addr exists that
546 does not equal 192.168.4.1". That is, as long as one ip.addr in the
547 packet does not equal 192.168.44.1, the packet passes the read
548 filter. The second filter "don't show me any packets that have at least
549 one ip.addr field equal to 192.168.4.1". If one ip.addr is 192.168.4.1,
550 the packet does not pass. If B<neither> ip.addr fields is 192.168.4.1,
551 then the packet passes.
553 It is easy to think of the 'ne' and 'eq' operators as having an implict
554 "exists" modifier when dealing with multiply-recurring fields. "ip.addr
555 ne 192.168.4.1" can be thought of as "there exists an ip.addr that does
556 not equal 192.168.4.1".
558 Be careful with multiply-recurring fields; they can be confusing.
560 Care must also be taken when using the read filter to remove noise
561 from the packet trace. If you want to e.g. filter out all IP multicast
562 packets to address 224.1.2.3, then using:
566 may be too restrictive. Filtering with "ip.dst" selects only those
567 B<IP> packets that satisfy the rule. Any other packets, including all
568 non-IP packets, will not printed. For printing also the non-IP
569 packets, you can use one of the following two expressions:
571 not ip or ip.dst ne 224.1.2.3
572 not ip.addr eq 224.1.2.3
574 The first filter uses "not ip" to include all non-IP packets and then
575 lets "ip.dst ne 224.1.2.3" to filter out the unwanted IP packets. The
576 second filter has already been explained above where filtering with
577 multiply occuring fields was discussed.
579 The following is a table of protocol and protocol fields that are
580 filterable in B<Tethereal>. The abbreviation of the protocol or field is
581 given. This abbreviation is what you use in the read filter. The
582 type of the field is also given.
584 =insert_dfilter_table
588 The F<ethereal.conf> file, which is installed in the F<etc> directory
589 under the main installation directory (for example, F</usr/local/etc>)
590 on UNIX-compatible systems, and in the main installation directory (for
591 example, F<C:\Program Files\Ethereal>) on Windows systems, and the
592 personal preferences file, which is F<$HOME/.ethereal/preferences> on
593 UNIX-compatible systems and F<%APPDATA%\Ethereal\preferences> (or, if
594 %APPDATA% isn't defined,
595 F<%USERPROFILE%\Application Data\Ethereal\preferences>) on
596 Windows systems, contain system-wide and personal preference settings,
597 respectively. The file contains preference settings of the form
598 I<prefname>B<:>I<value>, one per line, where I<prefname> is the name of
599 the preference (which is the same name that would appear in the
600 preference file), and I<value> is the value to which it should be set;
601 white space is allowed between B<:> and I<value>. A preference setting
602 can be continued on subsequent lines by indenting the continuation lines
603 with white space. A B<#> character starts a comment that runs to the
606 The system-wide preference file is read first, if it exists, overriding
607 B<Tethereal>'s default values; the personal preferences file is then
608 read, if it exists, overriding default values and values read from the
609 system-wide preference file.
611 The F<ethers> file, which is found in the F</etc> directory on
612 UNIX-compatible systems, and in the main installation directory (for
613 example, F<C:\Program Files\Ethereal>) on Windows systems, is consulted
614 to correlate 6-byte hardware addresses to names. If an address is not
615 found in the F<ethers> file, the F<$HOME/.ethereal/ethers> file on
616 UNIX-compatible systems, and the F<%APPDATA%\Ethereal\ethers> file (or, if
617 %APPDATA% isn't defined, the
618 F<%USERPROFILE%\Application Data\Ethereal\ethers> file) on Windows
619 systems is consulted next. Each line contains one hardware
620 address and name, separated by whitespace. The digits of the hardware
621 address are separated by either a colon (:), a dash (-), or a period
622 (.). The following three lines are valid lines of an ethers file:
624 ff:ff:ff:ff:ff:ff Broadcast
625 c0-00-ff-ff-ff-ff TR_broadcast
626 00.00.00.00.00.00 Zero_broadcast
628 The F<manuf> file, which is installed in the F<etc> directory under the
629 main installation directory (for example, F</usr/local/etc>) on
630 UNIX-compatible systems, and in the main installation directory (for
631 example, F<C:\Program Files\Ethereal>) on Windows systems, matches the
632 3-byte vendor portion of a 6-byte hardware address with the
633 manufacturer's name; it can also contain well-known MAC addresses and
634 address ranges specified with a netmask. The format of the file is the
635 same as the F<ethers> file, except that entries of the form
639 can be provided, with the 3-byte OUI and the name for a vendor, and
642 00-00-0C-07-AC/40 All-HSRP-routers
644 can be specified, with a MAC address and a mask indicating how many bits
645 of the address must match. Trailing zero bytes can be omitted from
646 address ranges. That entry, for example, will match addresses from
647 00-00-0C-07-AC-00 through 00-00-0C-07-AC-FF. The mask need not be a
650 The F<ipxnets> file, which is found in the F</etc> directory on
651 UNIX-compatible systems, and in the main installation directory (for
652 example, F<C:\Program Files\Ethereal>) on Windows systems, correlates
653 4-byte IPX network numbers to names. If a network number is not found
654 in the F<ipxnets> file, the F<$HOME/.ethereal/ipxnets> file on
655 UNIX-compatible systems, and the F<%APPDATA%\Ethereal\ipxnets> file (or,
656 if %APPDATA% isn't defined, the
657 F<%USERPROFILE%\Application Data\Ethereal\ipxnets> file)
658 on Windows systems, is consulted next. The format is the same as the
659 F<ethers> file, except that each address if four bytes instead of six.
660 Additionally, the address can be represented a single hexadecimal
661 number, as is more common in the IPX world, rather than four hex octets.
662 For example, these four lines are valid lines of an ipxnets file.
666 00:00:BE:EF IT_Server1
671 I<ethereal(1)>, I<editcap(1)>, I<tcpdump(8)>, I<pcap(3)>
675 B<Tethereal> is part of the B<Ethereal> distribution. The latest version
676 of B<Ethereal> can be found at B<http://www.ethereal.com>.
680 B<Tethereal> uses the same packet dissection code that B<Ethereal> does,
681 as well as using many other modules from B<Ethereal>; see the list of
682 authors in the B<Ethereal> man page for a list of authors of that code.