4 Note: This is just an ASCII snapshot of the faq and may not be up to
5 date. Please go to http://www.wireshark.org/faq.html for the up
6 to date version. The version of this snapshot can be found at
7 the end of this document.
14 1.1 What is Wireshark?
16 1.2 What's up with the name change? Is Wireshark a fork?
18 1.3 Where can I get help?
20 1.4 How much does Wireshark cost?
22 1.5 Can I use Wireshark commercially?
24 1.6 Can I use Wireshark as part of my commercial product?
26 1.7 What protocols are currently supported?
28 1.8 Are there any plans to support {your favorite protocol}?
30 1.9 Can Wireshark read capture files from {your favorite network
33 1.10 What devices can Wireshark use to capture packets?
35 1.11 Does Wireshark work on Windows Me?
37 1.12 Does Wireshark work on Windows XP?
39 2. Downloading Wireshark:
41 2.1 Why do I get an error when I try to run the Win32 installer?
43 3. Installing Wireshark:
45 3.1 I installed the Wireshark RPM (or other package); why did it
46 install TShark but not Wireshark?
48 4. Building Wireshark:
50 4.1 I have libpcap installed; why did the configure script not find
53 4.2 Why do I get the error
55 dftest_DEPENDENCIES was already defined in condition TRUE, which
56 implies condition HAVE_PLUGINS_TRUE
58 when I try to build Wireshark from SVN or a SVN snapshot?
60 4.3 Why does the linker fail with a number of "Output line too long."
61 messages followed by linker errors when I try to buil Wireshark?
63 4.4 When I try to build Wireshark on Solaris, why does the link fail
64 complaining that plugin_list is undefined?
66 4.5 When I try to build Wireshark on Windows, why does the build fail
67 because of conflicts between winsock.h and winsock2.h?
69 5. Starting Wireshark:
71 5.1 Why does Wireshark crash with a Bus Error when I try to run it on
74 5.2 When I run Wireshark on Windows NT, why does it die with a Dr.
75 Watson error, reporting an "Integer division by zero" exception, when I
78 5.3 When I try to run Wireshark, why does it complain about
79 sprint_realloc_objid being undefined?
81 5.4 When I try to run Wireshark on Windows, why does it fail to run
82 with a complaint that it can't find packet.dll?
84 5.5 I've installed Wireshark from Fink on Mac OS X; why is it very slow
87 6. Crashes and other fatal errors:
89 6.1 I have an XXX network card on my machine; if I try to capture on
90 it, why does my machine crash or reset itself?
92 6.2 Why does my machine crash or reset itself when I select "Start"
93 from the "Capture" menu or select "Preferences" from the "Edit" menu?
97 7.1 When I use Wireshark to capture packets, why do I see only packets
98 to and from my machine, or not see all the traffic I'm expecting to see
99 from or to the machine I'm trying to monitor?
101 7.2 When I capture with Wireshark, why can't I see any TCP packets
102 other than packets to and from my machine, even though another analyzer
103 on the network sees those packets?
105 7.3 Why am I only seeing ARP packets when I try to capture traffic?
107 7.4 Why am I not seeing any traffic when I try to capture traffic?
109 7.5 Can Wireshark capture on (my T1/E1 line, SS7 links, etc.)?
111 7.6 How do I put an interface into promiscuous mode?
113 7.7 I can set a display filter just fine; why don't capture filters
116 7.8 I'm entering valid capture filters; why do I still get "parse
119 7.9 How can I capture packets with CRC errors?
121 7.10 How can I capture entire frames, including the FCS?
123 7.11 I'm capturing packets on a machine on a VLAN; why don't the
124 packets I'm capturing have VLAN tags?
126 7.12 Why does Wireshark hang after I stop a capture?
128 8. Capturing packets on Windows:
130 8.1 I'm running Wireshark on Windows; why does some network interface
131 on my machine not show up in the list of interfaces in the "Interface:"
132 field in the dialog box popped up by "Capture->Start", and/or why does
133 Wireshark give me an error if I try to capture on that interface?
135 8.2 I'm running Wireshark on Windows; why do no network interfaces show
136 up in the list of interfaces in the "Interface:" field in the dialog
137 box popped up by "Capture->Start"?
139 8.3 I'm running Wireshark on Windows; why doesn't my serial port/ADSL
140 modem/ISDN modem show up in the list of interfaces in the "Interface:"
141 field in the dialog box popped up by "Capture->Start"?
143 8.4 I'm running Wireshark on Windows NT 4.0/Windows 2000/Windows
144 XP/Windows Server 2003; my machine has a PPP (dial-up POTS, ISDN, etc.)
145 interface, and it shows up in the "Interface" item in the "Capture
146 Options" dialog box. Why can no packets be sent on or received from
147 that network while I'm trying to capture traffic on that interface?
149 8.5 I'm running Wireshark on Windows 95/98/Me, on a machine with more
150 than one network adapter of the same type; why does Wireshark show all
151 of those adapters with the same name, not letting me use any of those
152 adapters other than the first one?
154 8.6 I'm running Wireshark on Windows; why am I not seeing any traffic
155 being sent by the machine running Wireshark?
157 8.7 When I capture on Windows in promiscuous mode, I can see packets
158 other than those sent to or from my machine; however, those packets
159 show up with a "Short Frame" indication, unlike packets to or from my
160 machine. What should I do to arrange that I see those packets in their
163 8.8 I'm capturing packets on {Windows 95, Windows 98, Windows Me}; why
164 are the time stamps on packets wrong?
166 8.9 I'm trying to capture 802.11 traffic on Windows; why am I not
169 8.10 I'm trying to capture 802.11 traffic on Windows; why am I seeing
170 packets received by the machine on which I'm capturing traffic, but not
171 packets sent by that machine?
173 8.11 I'm trying to capture Ethernet VLAN traffic on Windows, and I'm
174 capturing on a "raw" Ethernet device rather than a "VLAN interface", so
175 that I can see the VLAN headers; why am I seeing packets received by
176 the machine on which I'm capturing traffic, but not packets sent by
179 9. Capturing packets on UN*Xes:
181 9.1 I'm running Wireshark on a UNIX-flavored OS; why does some network
182 interface on my machine not show up in the list of interfaces in the
183 "Interface:" field in the dialog box popped up by "Capture->Start",
184 and/or why does Wireshark give me an error if I try to capture on that
187 9.2 I'm running Wireshark on a UNIX-flavored OS; why do no network
188 interfaces show up in the list of interfaces in the "Interface:" field
189 in the dialog box popped up by "Capture->Start"?
191 9.3 I'm capturing packets on Linux; why do the time stamps have only
192 100ms resolution, rather than 1us resolution?
194 10. Capturing packets on wireless LANs:
196 10.1 How can I capture raw 802.11 frames, including non-data
197 (management, beacon) frames?
199 10.2 How do I capture on an 802.11 device in monitor mode?
203 11.1 Why am I seeing lots of packets with incorrect TCP checksums?
205 11.2 I've just installed Wireshark, and the traffic on my local LAN is
206 boring. Where can I find more interesting captures?
208 11.3 Why doesn't Wireshark correctly identify RTP packets? It shows
211 11.4 Why doesn't Wireshark show Yahoo Messenger packets in captures
212 that contain Yahoo Messenger traffic?
214 12. Filtering traffic:
216 12.1 I saved a filter and tried to use its name to filter the display;
217 why do I get an "Unexpected end of filter string" error?
219 12.2 How can I search for, or filter, packets that have a particular
220 string anywhere in them?
222 12.3 How do I filter a capture to see traffic for virus XXX?
226 Q 1.1: What is Wireshark?
228 A: Gerald Combs, the creator of Ethereal®, has initiated the Wireshark
229 network protocol analyzer project, a successor to Ethereal®. The
230 Ethereal® core developer team has moved with Gerald to the Wireshark
231 project. It is the world's most popular network protocol analyzer. It
232 has a rich and powerful feature set, and runs on most computing
233 platforms including Windows, OS X, and Linux. It is freely available as
234 open source, and is released under the GNU General Public License.
236 For more information, please see the About Wireshark page.
238 Q 1.2: What's up with the name change? Is Wireshark a fork?
240 A: In May of 2006, the original author of Ethereal® went to work for
241 CACE Technologies (best known for WinPcap). Unfortunately, he had to
242 leave the Ethereal® trademarks behind.
244 This left the project in an awkward position. The only reasonable way
245 to ensure the continued success of the project was to change the name.
246 This is how Wireshark was born.
248 Wireshark is almost (but not quite) a fork. Normally a "fork" of an
249 open source project results in two names, web sites, development teams,
250 support infrastructures, etc. This is the case with Wireshark except
251 for one notable exception -- every member of the core development team
252 is now working on Wireshark. More information on the name change can be
257 Q 1.3: Where can I get help?
259 A: Community support is available on the wireshark-users mailing list.
260 Subscription information and archives for all of Wireshark's mailing
261 lists can be found at http://www.wireshark.org/mailman/listinfo. An IRC
262 channel dedicated to Wireshark can be found at
263 irc://irc.freenode.net/wireshark.
265 Commercial support, training, and development services are available
266 from CACE Technologies.
268 Q 1.4: How much does Wireshark cost?
270 A: Wireshark is "free software"; you can download it without paying any
271 license fee. The version of Wireshark you download isn't a "demo"
272 version, with limitations not present in a "full" version; it is the
275 The license under which Wireshark is issued is the GNU General Public
276 License. See the GNU GPL FAQ for some more information.
278 Q 1.5: Can I use Wireshark commercially?
280 A: Yes, if, for example, you mean "I work for a commercial
281 organization; can I use Wireshark to capture and analyze network
282 traffic in our company's networks or in our customer's networks?"
284 If you mean "Can I use Wireshark as part of my commercial product?",
285 see the next entry in the FAQ.
287 Q 1.6: Can I use Wireshark as part of my commercial product?
289 A: As noted, Wireshark is licensed under the GNU General Public
290 License. The GPL imposes conditions on your use of GPL'ed code in your
291 own products; you cannot, for example, make a "derived work" from
292 Wireshark, by making modifications to it, and then sell the resulting
293 derived work and not allow recipients to give away the resulting work.
294 You must also make the changes you've made to the Wireshark source
295 available to all recipients of your modified version; those changes
296 must also be licensed under the terms of the GPL. See the GPL FAQ for
297 more details; in particular, note the answer to the question about
298 modifying a GPLed program and selling it commercially, and the question
299 about linking GPLed code with other code to make a proprietary program.
301 You can combine a GPLed program such as Wireshark and a commercial
302 program as long as they communicate "at arm's length", as per this item
305 Q 1.7: What protocols are currently supported?
307 A: There are currently hundreds of supported protocols and media.
308 Details can be found in the wireshark(1) man page.
310 Q 1.8: Are there any plans to support {your favorite protocol}?
312 A: Support for particular protocols is added to Wireshark as a result
313 of people contributing that support; no formal plans for adding support
314 for particular protocols in particular future releases exist.
316 Q 1.9: Can Wireshark read capture files from {your favorite network
319 A: Support for particular protocols is added to Wireshark as a result
320 of people contributing that support; no formal plans for adding support
321 for particular protocols in particular future releases exist.
323 If a network analyzer writes out files in a format already supported by
324 Wireshark (e.g., in libpcap format), Wireshark may already be able to
325 read them, unless the analyzer has added its own proprietary extensions
328 If a network analyzer writes out files in its own format, or has added
329 proprietary extensions to another format, in order to make Wireshark
330 read captures from that network analyzer, we would either have to have
331 a specification for the file format, or the extensions, sufficient to
332 give us enough information to read the parts of the file relevant to
333 Wireshark, or would need at least one capture file in that format AND a
334 detailed textual analysis of the packets in that capture file (showing
335 packet time stamps, packet lengths, and the top-level packet header) in
336 order to reverse-engineer the file format.
338 Note that there is no guarantee that we will be able to
339 reverse-engineer a capture file format.
341 Q 1.10: What devices can Wireshark use to capture packets?
343 A: Wireshark can read live data from Ethernet, Token-Ring, FDDI, serial
344 (PPP and SLIP) (if the OS on which it's running allows Wireshark to do
345 so), 802.11 wireless LAN (if the OS on which it's running allows
346 Wireshark to do so), ATM connections (if the OS on which it's running
347 allows Wireshark to do so), and the "any" device supported on Linux by
348 recent versions of libpcap.
350 It can also read a variety of capture file formats, including:
351 * AG Group/WildPackets EtherPeek/TokenPeek/AiroPeek/EtherHelp/Packet
353 * AIX's iptrace captures
354 * Accellent's 5Views LAN agent output
355 * Cinco Networks NetXRay captures
356 * Cisco Secure Intrusion Detection System IPLog output
357 * CoSine L2 debug output
358 * DBS Etherwatch VMS text output
359 * Endace Measurement Systems' ERF format captures
360 * EyeSDN USB S0 traces
361 * HP-UX nettl captures
362 * ISDN4BSD project i4btrace captures
363 * Linux Bluez Bluetooth stack hcidump -w traces
364 * Lucent/Ascend router debug output
365 * Microsoft Network Monitor captures
366 * Network Associates Windows-based Sniffer captures
367 * Network General/Network Associates DOS-based Sniffer (compressed or
368 uncompressed) captures
369 * Network Instruments Observer version 9 captures
370 * Novell LANalyzer captures
371 * RADCOM's WAN/LAN analyzer captures
372 * Shomiti/Finisar Surveyor captures
373 * Toshiba's ISDN routers dump output
374 * VMS TCPIPtrace/TCPtrace/UCX$TRACE output
375 * Visual Networks' Visual UpTime traffic capture
376 * libpcap, tcpdump and various other tools using tcpdump's capture
378 * snoop and atmsnoop output
380 so that it can read traces from various network types, as captured by
381 other applications or equipment, even if it cannot itself capture on
384 Q 1.11: Does Wireshark work on Windows Me?
386 A: Yes, but if you want to capture packets, you will need to install
387 the latest version of WinPcap, as 2.02 and earlier versions of WinPcap
388 didn't support Windows Me. You should also install the latest version
389 of Wireshark as well.
391 Q 1.12: Does Wireshark work on Windows XP?
393 A: Yes, but if you want to capture packets, you will need to install
394 the latest version of WinPcap, as 2.2 and earlier versions of WinPcap
395 didn't support Windows XP.
397 2. Downloading Wireshark
399 Q 2.1: Why do I get an error when I try to run the Win32 installer?
401 A: The program you used to download it may have downloaded it
402 incorrectly. Web browsers sometimes may do this.
404 Try downloading it with, for example:
405 * Wget, for which Windows binaries are available on the SunSITE FTP
406 server at sunsite.tk or Heiko Herold's windows wget spot - wGetGUI
407 offers a GUI interface that uses wget;
408 * WS_FTP from Ipswitch,
409 * the ftp command that comes with Windows.
411 If you use the ftp command, make sure you do the transfer in binary
412 mode rather than ASCII mode, by using the binary command before
413 transferring the file.
415 3. Installing Wireshark
417 Q 3.1: I installed the Wireshark RPM (or other package); why did it
418 install TShark but not Wireshark?
420 A: Many distributions have separate Wireshark packages, one for non-GUI
421 components such as TShark, editcap, dumpcap, etc. and one for the GUI.
422 If this is the case on your system, there's probably a separate package
423 named wireshark-gnome or wireshark-gtk+. Find it and install it.
425 4. Building Wireshark
427 Q 4.1: I have libpcap installed; why did the configure script not find
430 A: Are you sure pcap.h and bpf.h are installed? The official
431 distribution of libpcap only installs the libpcap.a library file when
432 "make install" is run. To install pcap.h and bpf.h, you must run "make
433 install-incl". If you're running Debian or Redhat, make sure you have
434 the "libpcap-dev" or "libpcap-devel" packages installed.
436 It's also possible that pcap.h and bpf.h have been installed in a
437 strange location. If this is the case, you may have to tweak
440 Q 4.2: Why do I get the error
442 dftest_DEPENDENCIES was already defined in condition TRUE, which
443 implies condition HAVE_PLUGINS_TRUE
445 when I try to build Wireshark from SVN or a SVN snapshot?
447 A: You probably have automake 1.5 installed on your machine (the
448 command automake --version will report the version of automake on your
449 machine). There is a bug in that version of automake that causes this
450 problem; upgrade to a later version of automake (1.6 or later).
452 Q 4.3: Why does the linker fail with a number of "Output line too
453 long." messages followed by linker errors when I try to buil Wireshark?
455 A: The version of the sed command on your system is incapable of
456 handling very long lines. On Solaris, for example, /usr/bin/sed has a
457 line length limit too low to allow libtool to work; /usr/xpg4/bin/sed
458 can handle it, as can GNU sed if you have it installed.
460 On Solaris, changing your command search path to search /usr/xpg4/bin
461 before /usr/bin should make the problem go away; on any platform on
462 which you have this problem, installing GNU sed and changing your
463 command path to search the directory in which it is installed before
464 searching the directory with the version of sed that came with the OS
465 should make the problem go away.
467 Q 4.4: When I try to build Wireshark on Solaris, why does the link fail
468 complaining that plugin_list is undefined?
470 A: This appears to be due to a problem with some versions of the GTK+
471 and GLib packages from www.sunfreeware.org; un-install those packages,
472 and try getting the 1.2.10 versions from that site, or the versions
473 from The Written Word, or the versions from Sun's GNOME distribution,
474 or the versions from the supplemental software CD that comes with the
475 Solaris media kit, or build them from source from the GTK Web site.
476 Then re-run the configuration script, and try rebuilding Wireshark. (If
477 you get the 1.2.10 versions from www.sunfreeware.org, and the problem
478 persists, un-install them and try installing one of the other versions
481 Q 4.5: When I try to build Wireshark on Windows, why does the build
482 fail because of conflicts between winsock.h and winsock2.h?
484 A: As of Wireshark 0.9.5, you must install WinPcap 2.3 or later, and
485 the corresponding version of the developer's pack, in order to be able
486 to compile Wireshark; it will not compile with older versions of the
487 developer's pack. The symptoms of this failure are conflicts between
488 definitions in winsock.h and in winsock2.h; Wireshark uses winsock2.h,
489 but pre-2.3 versions of the WinPcap developer's packet use winsock.h.
490 (2.3 uses winsock2.h, so if Wireshark were to use winsock.h, it would
491 not be able to build with current versions of the WinPcap developer's
494 Note that the installed version of the developer's pack should be the
495 same version as the version of WinPcap you have installed.
497 5. Starting Wireshark
499 Q 5.1: Why does Wireshark crash with a Bus Error when I try to run it
502 A: Some versions of the GTK+ library from www.sunfreeware.org appear to
503 be buggy, causing Wireshark to drop core with a Bus Error. Un-install
504 those packages, and try getting the 1.2.10 version from that site, or
505 the version from The Written Word, or the version from Sun's GNOME
506 distribution, or the version from the supplemental software CD that
507 comes with the Solaris media kit, or build it from source from the GTK
508 Web site. Update the GLib library to the 1.2.10 version, from the same
509 source, as well. (If you get the 1.2.10 versions from
510 www.sunfreeware.org, and the problem persists, un-install them and try
511 installing one of the other versions mentioned.)
513 Similar problems may exist with older versions of GTK+ for earlier
516 Q 5.2: When I run Wireshark on Windows NT, why does it die with a Dr.
517 Watson error, reporting an "Integer division by zero" exception, when I
520 A: In at least some case, this appears to be due to using the default
521 VGA driver; if that's not the correct driver for your video card, try
522 running the correct driver for your video card.
524 Q 5.3: When I try to run Wireshark, why does it complain about
525 sprint_realloc_objid being undefined?
527 A: Wireshark can only be linked with version 4.2.2 or later of UCD
528 SNMP. Your version of Wireshark was dynamically linked with such a
529 version of UCD SNMP; however, you have an older version of UCD SNMP
530 installed, which means that when Wireshark is run, it tries to link to
531 the older version, and fails. You will have to replace that version of
532 UCD SNMP with version 4.2.2 or a later version.
534 Q 5.4: When I try to run Wireshark on Windows, why does it fail to run
535 with a complaint that it can't find packet.dll?
537 A: In older versions of Wireshark, there were two binary distributions
538 available for Windows, one that supported capturing packets, and one
539 that didn't. The version that supported capturing packets required that
540 you install the WinPcap driver; if you didn't install it, it would fail
541 to run because it couldn't find packet.dll.
543 The current version of Wireshark has only one binary distribution for
544 Windows; that version will check whether WinPcap is installed and, if
545 it's not, will disable support for packet capture.
547 The WinPcap driver and libraries can be downloaded from the WinPcap Web
548 site or the Wiretapped.net mirror of the WinPcap site.
550 Q 5.5: I've installed Wireshark from Fink on Mac OS X; why is it very
553 A: When an application is installed on OS X, prior to 10.4, it is
554 usually "prebound" to speed up launching the application. (That's what
555 the "Optimizing" phase of installation is.) Fink normally performs
556 prebinding automatically when you install a package. However, in some
557 rare cases, for whatever reason the prebinding caches get corrupt, and
558 then not only does prebinding fail, but startup actually becomes much
559 slower, because the system tries in vain to perform prebinding "on the
560 fly" as you launch the application. This fails, causing sometimes huge
561 delays. To fix the prebinding caches, run the command
562 sudo /sw/var/lib/fink/prebound/update-package-prebinding.pl -f
564 6. Crashes and other fatal errors
566 Q 6.1: I have an XXX network card on my machine; if I try to capture on
567 it, why does my machine crash or reset itself?
569 A: This is almost certainly a problem with one or more of:
570 * the operating system you're using;
571 * the device driver for the interface you're using;
572 * the libpcap/WinPcap library and, if this is Windows, the WinPcap
576 * if you are using Windows, see the WinPcap support page - check the
577 "Submitting bugs" section;
578 * if you are using some Linux distribution, some version of BSD, or
579 some other UNIX-flavored OS, you should report the problem to the
580 company or organization that produces the OS (in the case of a
581 Linux distribution, report the problem to whoever produces the
584 Q 6.2: Why does my machine crash or reset itself when I select "Start"
585 from the "Capture" menu or select "Preferences" from the "Edit" menu?
587 A: Both of those operations cause Wireshark to try to build a list of
588 the interfaces that it can open; it does so by getting a list of
589 interfaces and trying to open them. There is probably an OS, driver,
590 or, for Windows, WinPcap bug that causes the system to crash when this
591 happens; see the previous question.
595 Q 7.1: When I use Wireshark to capture packets, why do I see only
596 packets to and from my machine, or not see all the traffic I'm
597 expecting to see from or to the machine I'm trying to monitor?
599 A: This might be because the interface on which you're capturing is
600 plugged into an Ethernet or Token Ring switch; on a switched network,
601 unicast traffic between two ports will not necessarily appear on other
602 ports - only broadcast and multicast traffic will be sent to all ports.
604 Note that even if your machine is plugged into a hub, the "hub" may be
605 a switched hub, in which case you're still on a switched network.
607 Note also that on the Linksys Web site, they say that their
608 auto-sensing hubs "broadcast the 10Mb packets to the port that operate
609 at 10Mb only and broadcast the 100Mb packets to the ports that operate
610 at 100Mb only", which would indicate that if you sniff on a 10Mb port,
611 you will not see traffic coming sent to a 100Mb port, and vice versa.
612 This problem has also been reported for Netgear dual-speed hubs, and
613 may exist for other "auto-sensing" or "dual-speed" hubs.
615 Some switches have the ability to replicate all traffic on all ports to
616 a single port so that you can plug your analyzer into that single port
617 to sniff all traffic. You would have to check the documentation for the
618 switch to see if this is possible and, if so, to see how to do this.
619 See the switch reference page on the Wireshark Wiki for information on
620 some switches. (Note that it's a Wiki, so you can update or fix that
621 information, or add additional information on those switches or
622 information on new switches, yourself.)
624 Note also that many firewall/NAT boxes have a switch built into them;
625 this includes many of the "cable/DSL router" boxes. If you have a box
626 of that sort, that has a switch with some number of Ethernet ports into
627 which you plug machines on your network, and another Ethernet port used
628 to connect to a cable or DSL modem, you can, at least, sniff traffic
629 between the machines on your network and the Internet by plugging the
630 Ethernet port on the router going to the modem, the Ethernet port on
631 the modem, and the machine on which you're running Wireshark into a hub
632 (make sure it's not a switching hub, and that, if it's a dual-speed
633 hub, all three of those ports are running at the same speed.
635 If your machine is not plugged into a switched network or a dual-speed
636 hub, or it is plugged into a switched network but the port is set up to
637 have all traffic replicated to it, the problem might be that the
638 network interface on which you're capturing doesn't support
639 "promiscuous" mode, or because your OS can't put the interface into
640 promiscuous mode. Normally, network interfaces supply to the host only:
641 * packets sent to one of that host's link-layer addresses;
643 * multicast packets sent to a multicast address that the host has
644 configured the interface to accept.
646 Most network interfaces can also be put in "promiscuous" mode, in which
647 they supply to the host all network packets they see. Wireshark will
648 try to put the interface on which it's capturing into promiscuous mode
649 unless the "Capture packets in promiscuous mode" option is turned off
650 in the "Capture Options" dialog box, and TShark will try to put the
651 interface on which it's capturing into promiscuous mode unless the -p
652 option was specified. However, some network interfaces don't support
653 promiscuous mode, and some OSes might not allow interfaces to be put
654 into promiscuous mode.
656 If the interface is not running in promiscuous mode, it won't see any
657 traffic that isn't intended to be seen by your machine. It will see
658 broadcast packets, and multicast packets sent to a multicast MAC
659 address the interface is set up to receive.
661 You should ask the vendor of your network interface whether it supports
662 promiscuous mode. If it does, you should ask whoever supplied the
663 driver for the interface (the vendor, or the supplier of the OS you're
664 running on your machine) whether it supports promiscuous mode with that
667 In the case of token ring interfaces, the drivers for some of them, on
668 Windows, may require you to enable promiscuous mode in order to capture
669 in promiscuous mode. See the Wireshark Wiki item on Token Ring
670 capturing for details.
672 In the case of wireless LAN interfaces, it appears that, when those
673 interfaces are promiscuously sniffing, they're running in a
674 significantly different mode from the mode that they run in when
675 they're just acting as network interfaces (to the extent that it would
676 be a significant effor for those drivers to support for promiscuously
677 sniffing and acting as regular network interfaces at the same time), so
678 it may be that Windows drivers for those interfaces don't support
681 Q 7.2: When I capture with Wireshark, why can't I see any TCP packets
682 other than packets to and from my machine, even though another analyzer
683 on the network sees those packets?
685 A: You're probably not seeing any packets other than unicast packets to
686 or from your machine, and broadcast and multicast packets; a switch
687 will normally send to a port only unicast traffic sent to the MAC
688 address for the interface on that port, and broadcast and multicast
689 traffic - it won't send to that port unicast traffic sent to a MAC
690 address for some other interface - and a network interface not in
691 promiscuous mode will receive only unicast traffic sent to the MAC
692 address for that interface, broadcast traffic, and multicast traffic
693 sent to a multicast MAC address the interface is set up to receive.
695 TCP doesn't use broadcast or multicast, so you will only see your own
696 TCP traffic, but UDP services may use broadcast or multicast so you'll
697 see some UDP traffic - however, this is not a problem with TCP traffic,
698 it's a problem with unicast traffic, as you also won't see all UDP
699 traffic between other machines.
701 I.e., this is probably the same question as this earlier one; see the
702 response to that question.
704 Q 7.3: Why am I only seeing ARP packets when I try to capture traffic?
706 A: You're probably on a switched network, and running Wireshark on a
707 machine that's not sending traffic to the switch and not being sent any
708 traffic from other machines on the switch. ARP packets are often
709 broadcast packets, which are sent to all switch ports.
711 I.e., this is probably the same question as this earlier one; see the
712 response to that question.
714 Q 7.4: Why am I not seeing any traffic when I try to capture traffic?
716 A: Is the machine running Wireshark sending out any traffic on the
717 network interface on which you're capturing, or receiving any traffic
718 on that network, or is there any broadcast traffic on the network or
719 multicast traffic to a multicast group to which the machine running
722 If not, this may just be a problem with promiscuous sniffing, either
723 due to running on a switched network or a dual-speed hub, or due to
724 problems with the interface not supporting promiscuous mode; see the
725 response to this earlier question.
727 Otherwise, on Windows, see the response to this question and, on a
728 UNIX-flavored OS, see the response to this question.
730 Q 7.5: Can Wireshark capture on (my T1/E1 line, SS7 links, etc.)?
732 A: Wireshark can only capture on devices supported by libpcap/WinPcap.
733 On most OSes, only devices that can act as network interfaces of the
734 type that support IP are supported as capture devices for
735 libpcap/WinPcap, although the device doesn't necessarily have to be
736 running as an IP interface in order to support traffic capture.
738 On Linux and FreeBSD, libpcap 0.8 and later support the API for Endace
739 Measurement Systems' DAG cards, so that a system with one of those
740 cards, and its driver and libraries, installed can capture traffic with
741 those cards with libpcap-based applications. You would either have to
742 have a version of Wireshark built with that version of libpcap, or a
743 dynamically-linked version of Wireshark and a shared libpcap library
744 with DAG support, in order to do so with Wireshark. You should ask
745 Endace whether that could be used to capture traffic on, for example,
746 your T1/E1 link. See the SS7 capture setup page on the Wireshark Wiki
747 for current information on capturing SS7 traffic on TDM links.
749 Q 7.6: How do I put an interface into promiscuous mode?
751 A: By not disabling promiscuous mode when running Wireshark or TShark.
754 * the form of promiscuous mode that libpcap (the library that
755 programs such as tcpdump, Wireshark, etc. use to do packet capture)
756 turns on will not necessarily be shown if you run ifconfig on the
757 interface on a UNIX system;
758 * some network interfaces might not support promiscuous mode, and
759 some drivers might not allow promiscuous mode to be turned on - see
760 this earlier question for more information on that;
761 * the fact that you're not seeing any traffic, or are only seeing
762 broadcast traffic, or aren't seeing any non-broadcast traffic other
763 than traffic to or from the machine running Wireshark, does not
764 mean that promiscuous mode isn't on - see this earlier question for
765 more information on that.
767 I.e., this is probably the same question as this earlier one; see the
768 response to that question.
770 Q 7.7: I can set a display filter just fine; why don't capture filters
773 A: Capture filters currently use a different syntax than display
774 filters. Here's the corresponding section from the wireshark(1) man
777 "Display filters in Wireshark are very powerful; more fields are
778 filterable in Wireshark than in other protocol analyzers, and the
779 syntax you can use to create your filters is richer. As Wireshark
780 progresses, expect more and more protocol fields to be allowed in
783 Packet capturing is performed with the pcap library. The capture filter
784 syntax follows the rules of the pcap library. This syntax is different
785 from the display filter syntax."
787 The capture filter syntax used by libpcap can be found in the
790 Q 7.8: I'm entering valid capture filters; why do I still get "parse
793 A: There is a bug in some versions of libpcap/WinPcap that cause it to
794 report parse errors even for valid expressions if a previous filter
795 expression was invalid and got a parse error.
797 Try exiting and restarting Wireshark; if you are using a version of
798 libpcap/WinPcap with this bug, this will "erase" its memory of the
799 previous parse error. If the capture filter that got the "parse error"
800 now works, the earlier error with that filter was probably due to this
803 The bug was fixed in libpcap 0.6; 0.4[.x] and 0.5[.x] versions of
804 libpcap have this bug, but 0.6[.x] and later versions don't.
806 Versions of WinPcap prior to 2.3 are based on pre-0.6 versions of
807 libpcap, and have this bug; WinPcap 2.3 is based on libpcap 0.6.2, and
808 doesn't have this bug.
810 If you are running Wireshark on a UNIX-flavored platform, run
811 "wireshark -v", or select "About Wireshark..." from the "Help" menu in
812 Wireshark, to see what version of libpcap it's using. If it's not 0.6
813 or later, you will need either to upgrade your OS to get a later
814 version of libpcap, or will need to build and install a later version
815 of libpcap from the tcpdump.org Web site and then recompile Wireshark
816 from source with that later version of libpcap.
818 If you are running Wireshark on Windows with a pre-2.3 version of
819 WinPcap, you will need to un-install WinPcap and then download and
822 Q 7.9: How can I capture packets with CRC errors?
824 A: Wireshark can capture only the packets that the packet capture
825 library - libpcap on UNIX-flavored OSes, and the WinPcap port to
826 Windows of libpcap on Windows - can capture, and libpcap/WinPcap can
827 capture only the packets that the OS's raw packet capture mechanism (or
828 the WinPcap driver, and the underlying OS networking code and network
829 interface drivers, on Windows) will allow it to capture.
831 Unless the OS always supplies packets with errors such as invalid CRCs
832 to the raw packet capture mechanism, or can be configured to do so,
833 invalid CRCs to the raw packet capture mechanism, Wireshark - and other
834 programs that capture raw packets, such as tcpdump - cannot capture
835 those packets. You will have to determine whether your OS needs to be
836 so configured and, if so, can be so configured, configure it if
837 necessary and possible, and make whatever changes to libpcap and the
838 packet capture program you're using are necessary, if any, to support
839 capturing those packets.
841 Most OSes probably do not support capturing packets with invalid CRCs
842 on Ethernet, and probably do not support it on most other link-layer
843 types. Some drivers on some OSes do support it, such as some Ethernet
844 drivers on FreeBSD; in those OSes, you might always get those packets,
845 or you might only get them if you capture in promiscuous mode (you'd
846 have to determine which is the case).
848 Note that libpcap does not currently supply to programs that use it an
849 indication of whether the packet's CRC was invalid (because the drivers
850 themselves do not supply that information to the raw packet capture
851 mechanism); therefore, Wireshark will not indicate which packets had
852 CRC errors unless the FCS was captured (see the next question) and
853 you're using Wireshark 0.9.15 and later, in which case Wireshark will
854 check the CRC and indicate whether it's correct or not.
856 Q 7.10: How can I capture entire frames, including the FCS?
858 A: Wireshark can only capture data that the packet capture library -
859 libpcap on UNIX-flavored OSes, and the WinPcap port to Windows of
860 libpcap on Windows - can capture, and libpcap/WinPcap can capture only
861 the data that the OS's raw packet capture mechanism (or the WinPcap
862 driver, and the underlying OS networking code and network interface
863 drivers, on Windows) will allow it to capture.
865 For any particular link-layer network type, unless the OS supplies the
866 FCS of a frame as part of the frame, or can be configured to do so,
867 Wireshark - and other programs that capture raw packets, such as
868 tcpdump - cannot capture the FCS of a frame. You will have to determine
869 whether your OS needs to be so configured and, if so, can be so
870 configured, configure it if necessary and possible, and make whatever
871 changes to libpcap and the packet capture program you're using are
872 necessary, if any, to support capturing the FCS of a frame.
874 Most OSes do not support capturing the FCS of a frame on Ethernet, and
875 probably do not support it on most other link-layer types. Some drivres
876 on some OSes do support it, such as some (all?) Ethernet drivers on
877 NetBSD and possibly the driver for Apple's gigabit Ethernet interface
878 in Mac OS X; in those OSes, you might always get the FCS, or you might
879 only get the FCS if you capture in promiscuous mode (you'd have to
880 determine which is the case).
882 Versions of Wireshark prior to 0.9.15 will not treat an Ethernet FCS in
883 a captured packet as an FCS. 0.9.15 and later will attempt to determine
884 whether there's an FCS at the end of the frame and, if it thinks there
885 is, will display it as such, and will check whether it's the correct
888 Q 7.11: I'm capturing packets on a machine on a VLAN; why don't the
889 packets I'm capturing have VLAN tags?
891 A: You might be capturing on what might be called a "VLAN interface" -
892 the way a particular OS makes VLANs plug into the networking stack
893 might, for example, be to have a network device object for the physical
894 interface, which takes VLAN packets, strips off the VLAN header and
895 constructs an Ethernet header, and passes that packet to an internal
896 network device object for the VLAN, which then passes the packets onto
897 various higher-level protocol implementations.
899 In order to see the raw Ethernet packets, rather than "de-VLANized"
900 packets, you would have to capture not on the virtual interface for the
901 VLAN, but on the interface corresponding to the physical network
902 device, if possible. See the Wireshark Wiki item on VLAN capturing for
905 Q 7.12: Why does Wireshark hang after I stop a capture?
907 A: The most likely reason for this is that Wireshark is trying to look
908 up an IP address in the capture to convert it to a name (so that, for
909 example, it can display the name in the source address or destination
910 address columns), and that lookup process is taking a very long time.
912 Wireshark calls a routine in the OS of the machine on which it's
913 running to convert of IP addresses to the corresponding names. That
914 routine probably does one or more of:
915 * a search of a system file listing IP addresses and names;
916 * a lookup using DNS;
917 * on UNIX systems, a lookup using NIS;
918 * on Windows systems, a NetBIOS-over-TCP query.
920 If a DNS server that's used in an address lookup is not responding, the
921 lookup will fail, but will only fail after a timeout while the system
922 routine waits for a reply.
924 In addition, on Windows systems, if the DNS lookup of the address
925 fails, either because the server isn't responding or because there are
926 no records in the DNS that could be used to map the address to a name,
927 a NetBIOS-over-TCP query will be made. That query involves sending a
928 message to the NetBIOS-over-TCP name service on that machine, asking
929 for the name and other information about the machine. If the machine
930 isn't running software that responds to those queries - for example,
931 many non-Windows machines wouldn't be running that software - the
932 lookup will only fail after a timeout. Those timeouts can cause the
933 lookup to take a long time.
935 If you disable network address-to-name translation - for example, by
936 turning off the "Enable network name resolution" option in the "Capture
937 Options" dialog box for starting a network capture - the lookups of the
938 address won't be done, which may speed up the process of reading the
939 capture file after the capture is stopped. You can make that setting
940 the default by selecting "Preferences" from the "Edit" menu, turning
941 off the "Enable network name resolution" option in the "Name
942 resolution" options in the preferences disalog box, and using the
943 "Save" button in that dialog box; note that this will save all your
944 current preference settings.
946 If Wireshark hangs when reading a capture even with network name
947 resolution turned off, there might, for example, be a bug in one of
948 Wireshark's dissectors for a protocol causing it to loop infinitely. If
949 you're not running the most recent release of Wireshark, you should
950 first upgrade to that release, as, if there's a bug of that sort, it
951 might've been fixed in a release after the one you're running. If the
952 hang occurs in the most recent release of Wireshark, the bug should be
953 reported to the Wireshark developers' mailing list at
954 wireshark-dev@wireshark.org.
956 On UNIX-flavored OSes, please try to force Wireshark to dump core, by
957 sending it a SIGABRT signal (usually signal 6) with the kill command,
958 and then get a stack trace if you have a debugger installed. A stack
959 trace can be obtained by using your debugger (gdb in this example), the
960 Wireshark binary, and the resulting core file. Here's an example of how
961 to use the gdb command backtrace to do so.
964 ..... prints the stack trace
968 The core dump file may be named "wireshark.core" rather than "core" on
969 some platforms (e.g., BSD systems).
971 Also, if at all possible, please send a copy of the capture file that
972 caused the problem; when capturing packets, Wireshark normally writes
973 captured packets to a temporary file, which will probably be in /tmp or
974 /var/tmp on UNIX-flavored OSes, \TEMP on the main system disk (normally
975 C:) on Windows 9x/Me/NT 4.0, and \Documents and Settings\your login
976 name\Local Settings\Temp on the main system disk on Windows
977 2000/Windows XP/Windows Server 2003, so the capture file will probably
978 be there. It will have a name beginning with ether, with some mixture
979 of letters and numbers after that. Please don't send a trace file
980 greater than 1 MB when compressed; instead, make it available via FTP
981 or HTTP, or say it's available but leave it up to a developer to ask
982 for it. If the trace file contains sensitive information (e.g.,
983 passwords), then please do not send it.
985 8. Capturing packets on Windows
987 Q 8.1: I'm running Wireshark on Windows; why does some network
988 interface on my machine not show up in the list of interfaces in the
989 "Interface:" field in the dialog box popped up by "Capture->Start",
990 and/or why does Wireshark give me an error if I try to capture on that
993 A: If you are running Wireshark on Windows NT 4.0, Windows 2000,
994 Windows XP, or Windows Server 2003, and this is the first time you have
995 run a WinPcap-based program (such as Wireshark, or TShark, or WinDump,
996 or Analyzer, or...) since the machine was rebooted, you need to run
997 that program from an account with administrator privileges; once you
998 have run such a program, you will not need administrator privileges to
999 run any such programs until you reboot.
1001 If you are running on Windows 95/98/Me, or if you are running on
1002 Windows NT 4.0/Windows 2000/Windows XP/Windows Server 2003 and have
1003 administrator privileges or a WinPcap-based program has been run with
1004 those privileges since the machine rebooted, this problem might clear
1005 up if you completely un-install WinPcap and then re-install it.
1007 If that doesn't work, then note that Wireshark relies on the WinPcap
1008 library, on the WinPcap device driver, and on the facilities that come
1009 with the OS on which it's running in order to do captures.
1011 Therefore, if the OS, the WinPcap library, or the WinPcap driver don't
1012 support capturing on a particular network interface device, Wireshark
1013 won't be able to capture on that device.
1016 1. 2.02 and earlier versions of the WinPcap driver and library that
1017 Wireshark uses for packet capture didn't support Token Ring
1018 interfaces; versions 2.1 and later support Token Ring, and the
1019 current version of Wireshark works with (and, in fact, requires)
1020 WinPcap 2.1 or later.
1021 If you are having problems capturing on Token Ring interfaces, and
1022 you have WinPcap 2.02 or an earlier version of WinPcap installed,
1023 you should uninstall WinPcap, download and install the current
1024 version of WinPcap, and then install the latest version of
1026 2. On Windows 95, 98, or Me, sometimes more than one interface will be
1027 given the same name; if that is the case, you will only be able to
1028 capture on one of those interfaces - it's not clear to which one
1029 the name, when used in a WinPcap-based application, will refer. For
1030 example, if you have a PPP serial interface and a VPN interface,
1031 they might show up with the same name, for example "ppp-mac", and
1032 if you try to capture on "ppp-mac", it might not capture on the
1033 interface you're currently using. In that case, you might, for
1034 example, have to remove the VPN interface from the system in order
1035 to capture on the PPP serial interface.
1036 3. WinPcap 2.3 has problems supporting PPP WAN interfaces on Windows
1037 NT 4.0, Windows 2000, Windows XP, and Windows Server 2003, and, to
1038 avoid those problems, support for PPP WAN interfaces on those
1039 versions of Windows has been disabled in WinPcap 3.0. Regular
1040 dial-up lines, ISDN lines, ADSL connections using PPPoE or PPPoA,
1041 and various other lines such as T1/E1 lines are all PPP interfaces,
1042 so those interfaces might not show up on the list of interfaces in
1043 the "Capture Options" dialog on those OSes.
1044 On Windows 2000, Windows XP, and Windows Server 2003, but not
1045 Windows NT 4.0 or Windows Vista Beta 1, you should be able to
1046 capture on the "GenericDialupAdapter" with WinPcap 3.1. (3.1 beta
1047 releases called it the "NdisWanAdapter"; if you're using a 3.1 beta
1048 release, you should un-install it and install the final 3.1
1049 release.) See the Wireshark Wiki item on PPP capturing for details.
1050 4. WinPcap prior to 3.0 does not support multiprocessor machines (note
1051 that machines with a single multi-threaded processor, such as
1052 Intel's new multi-threaded x86 processors, are multiprocessor
1053 machines as far as the OS and WinPcap are concerned), and recent
1054 2.x versions of WinPcap refuse to operate if they detect that
1055 they're running on a multiprocessor machine, which means that they
1056 may not show any network interfaces. You will need to use WinPcap
1057 3.0 to capture on a multiprocessor machine.
1059 If an interface doesn't show up in the list of interfaces in the
1060 "Interface:" field, and you know the name of the interface, try
1061 entering that name in the "Interface:" field and capturing on that
1064 If the attempt to capture on it succeeds, the interface is somehow not
1065 being reported by the mechanism Wireshark uses to get a list of
1066 interfaces. Try listing the interfaces with WinDump; see the WinDump
1067 Web site for information on using WinDump.
1069 You would run WinDump with the -D flag; if it lists the interface,
1070 please report this to wireshark-dev@wireshark.org giving full details
1071 of the problem, including
1072 * the operating system you're using, and the version of that
1074 * the type of network device you're using;
1075 * the output of WinDump.
1077 If WinDump does not list the interface, this is almost certainly a
1078 problem with one or more of:
1079 * the operating system you're using;
1080 * the device driver for the interface you're using;
1081 * the WinPcap library and/or the WinPcap device driver;
1083 so first check the WinPcap FAQ or the Wiretapped.net mirror of that
1084 FAQ, to see if your problem is mentioned there. If not, then see the
1085 WinPcap support page - check the "Submitting bugs" section.
1087 If you are having trouble capturing on a particular network interface,
1088 first try capturing on that device with WinDump; see the WinDump Web
1089 site for information on using WinDump.
1091 If you can capture on the interface with WinDump, send mail to
1092 wireshark-users@wireshark.org giving full details of the problem,
1094 * the operating system you're using, and the version of that
1096 * the type of network device you're using;
1097 * the error message you get from Wireshark.
1099 If you cannot capture on the interface with WinDump, this is almost
1100 certainly a problem with one or more of:
1101 * the operating system you're using;
1102 * the device driver for the interface you're using;
1103 * the WinPcap library and/or the WinPcap device driver;
1105 so first check the WinPcap FAQ or the Wiretapped.net mirror of that
1106 FAQ, to see if your problem is mentioned there. If not, then see the
1107 WinPcap support page - check the "Submitting bugs" section.
1109 You may also want to ask the wireshark-users@wireshark.org and the
1110 winpcap-users@winpcap.org mailing lists to see if anybody happens to
1111 know about the problem and know a workaround or fix for the problem.
1112 (Note that you will have to subscribe to that list in order to be
1113 allowed to mail to it; see the WinPcap support page for information on
1114 the mailing list.) In your mail, please give full details of the
1115 problem, as described above, and also indicate that the problem occurs
1116 with WinDump, not just with Wireshark.
1118 Q 8.2: I'm running Wireshark on Windows; why do no network interfaces
1119 show up in the list of interfaces in the "Interface:" field in the
1120 dialog box popped up by "Capture->Start"?
1122 A: This is really the same question as the previous one; see the
1123 response to that question.
1125 Q 8.3: I'm running Wireshark on Windows; why doesn't my serial
1126 port/ADSL modem/ISDN modem show up in the list of interfaces in the
1127 "Interface:" field in the dialog box popped up by "Capture->Start"?
1129 A: Internet access on those devices is often done with the
1130 Point-to-Point (PPP) protocol; WinPcap 2.3 has problems supporting PPP
1131 WAN interfaces on Windows NT 4.0, Windows 2000, Windows XP, and Windows
1132 Server 2003, and, to avoid those problems, support for PPP WAN
1133 interfaces on those versions of Windows has been disabled in WinPcap
1136 On Windows 2000, Windows XP, and Windows Server 2003, but not Windows
1137 NT 4.0 or Windows Vista Beta 1, you should be able to capture on the
1138 "GenericDialupAdapter" with WinPcap 3.1. (3.1 beta releases called it
1139 the "NdisWanAdapter"; if you're using a 3.1 beta release, you should
1140 un-install it and install the final 3.1 release.) See the Wireshark
1141 Wiki item on PPP capturing for details.
1143 Q 8.4: I'm running Wireshark on Windows NT 4.0/Windows 2000/Windows
1144 XP/Windows Server 2003; my machine has a PPP (dial-up POTS, ISDN, etc.)
1145 interface, and it shows up in the "Interface" item in the "Capture
1146 Options" dialog box. Why can no packets be sent on or received from
1147 that network while I'm trying to capture traffic on that interface?
1149 A: Some versions of WinPcap have problems with PPP WAN interfaces on
1150 Windows NT 4.0, Windows 2000, Windows XP, and Windows Server 2003; one
1151 symptom that may be seen is that attempts to capture in promiscuous
1152 mode on the interface cause the interface to be incapable of sending or
1153 receiving packets. You can disable promiscuous mode using the -p
1154 command-line flag or the item in the "Capture Preferences" dialog box,
1155 but this may mean that outgoing packets, or incoming packets, won't be
1156 seen in the capture.
1158 On Windows 2000, Windows XP, and Windows Server 2003, but not Windows
1159 NT 4.0 or Windows Vista Beta 1, you should be able to capture on the
1160 "GenericDialupAdapter" with WinPcap 3.1. (3.1 beta releases called it
1161 the "NdisWanAdapter"; if you're using a 3.1 beta release, you should
1162 un-install it and install the final 3.1 release.) See the Wireshark
1163 Wiki item on PPP capturing for details.
1165 Q 8.5: I'm running Wireshark on Windows 95/98/Me, on a machine with
1166 more than one network adapter of the same type; why does Wireshark show
1167 all of those adapters with the same name, not letting me use any of
1168 those adapters other than the first one?
1170 A: Unfortunately, Windows 95/98/Me gives the same name to multiple
1171 instances of the type of same network adapter. Therefore, WinPcap
1172 cannot distinguish between them, so a WinPcap-based application can
1173 capture only on the first such interface; Wireshark is a
1174 libpcap/WinPcap-based application.
1176 Q 8.6: I'm running Wireshark on Windows; why am I not seeing any
1177 traffic being sent by the machine running Wireshark?
1179 A: If you are running some form of VPN client software, it might be
1180 causing this problem; people have seen this problem when they have
1181 Check Point's VPN software installed on their machine. If that's the
1182 cause of the problem, you will have to remove the VPN software in order
1183 to have Wireshark (or any other application using WinPcap) see outgoing
1184 packets; unfortunately, neither we nor the WinPcap developers know any
1185 way to make WinPcap and the VPN software work well together.
1187 Also, some drivers for Windows (especially some wireless network
1188 interface drivers) apparently do not, when running in promiscuous mode,
1189 arrange that outgoing packets are delivered to the software that
1190 requested that the interface run promiscuously; try turning promiscuous
1193 Q 8.7: When I capture on Windows in promiscuous mode, I can see packets
1194 other than those sent to or from my machine; however, those packets
1195 show up with a "Short Frame" indication, unlike packets to or from my
1196 machine. What should I do to arrange that I see those packets in their
1199 A: In at least some cases, this appears to be the result of PGPnet
1200 running on the network interface on which you're capturing; turn it off
1203 Q 8.8: I'm capturing packets on {Windows 95, Windows 98, Windows Me};
1204 why are the time stamps on packets wrong?
1206 A: This is due to a bug in WinPcap. The bug should be fixed in WinPcap
1207 3.0 and later releases.
1209 Q 8.9: I'm trying to capture 802.11 traffic on Windows; why am I not
1212 A: At least some 802.11 card drivers on Windows appear not to see any
1213 packets if they're running in promiscuous mode. Try turning promiscuous
1214 mode off; you'll only be able to see packets sent by and received by
1215 your machine, not third-party traffic, and it'll look like Ethernet
1216 traffic and won't include any management or control frames, but that's
1217 a limitation of the card drivers.
1219 See MicroLogix's list of cards supported with WinPcap for information
1220 on support of various adapters and drivers with WinPcap.
1222 Q 8.10: I'm trying to capture 802.11 traffic on Windows; why am I
1223 seeing packets received by the machine on which I'm capturing traffic,
1224 but not packets sent by that machine?
1226 A: This appears to be another problem with promiscuous mode; try
1229 Q 8.11: I'm trying to capture Ethernet VLAN traffic on Windows, and I'm
1230 capturing on a "raw" Ethernet device rather than a "VLAN interface", so
1231 that I can see the VLAN headers; why am I seeing packets received by
1232 the machine on which I'm capturing traffic, but not packets sent by
1235 A: The way the Windows networking code works probably means that
1236 packets are sent on a "VLAN interface" rather than the "raw" device, so
1237 packets sent by the machine will only be seen when you capture on the
1238 "VLAN interface". If so, you will be unable to see outgoing packets
1239 when capturing on the "raw" device, so you are stuck with a choice
1240 between seeing VLAN headers and seeing outgoing packets.
1242 9. Capturing packets on UN*Xes
1244 Q 9.1: I'm running Wireshark on a UNIX-flavored OS; why does some
1245 network interface on my machine not show up in the list of interfaces
1246 in the "Interface:" field in the dialog box popped up by
1247 "Capture->Start", and/or why does Wireshark give me an error if I try
1248 to capture on that interface?
1250 A: You may need to run Wireshark from an account with sufficient
1251 privileges to capture packets, such as the super-user account, or may
1252 need to give your account sufficient privileges to capture packets.
1253 Only those interfaces that Wireshark can open for capturing show up in
1254 that list; if you don't have sufficient privileges to capture on any
1255 interfaces, no interfaces will show up in the list. See the Wireshark
1256 Wiki item on capture privileges for details on how to give a particular
1257 account or account group capture privileges on platforms where that can
1260 If you are running Wireshark from an account with sufficient
1261 privileges, then note that Wireshark relies on the libpcap library, and
1262 on the facilities that come with the OS on which it's running in order
1263 to do captures. On some OSes, those facilities aren't present by
1264 default; see the Wireshark Wiki item on adding capture support for
1267 And, even if you're running with an account that has sufficient
1268 privileges to capture, and capture support is present in your OS, if
1269 the OS or the libpcap library don't support capturing on a particular
1270 network interface device or particular types of devices, Wireshark
1271 won't be able to capture on that device.
1273 On Solaris, note that libpcap 0.6.2 and earlier didn't support Token
1274 Ring interfaces; the current version, 0.7.2, does support Token Ring,
1275 and the current version of Wireshark works with libcap 0.7.2 and later.
1277 If an interface doesn't show up in the list of interfaces in the
1278 "Interface:" field, and you know the name of the interface, try
1279 entering that name in the "Interface:" field and capturing on that
1282 If the attempt to capture on it succeeds, the interface is somehow not
1283 being reported by the mechanism Wireshark uses to get a list of
1284 interfaces; please report this to wireshark-dev@wireshark.org giving
1285 full details of the problem, including
1286 * the operating system you're using, and the version of that
1287 operating system (for Linux, give both the version number of the
1288 kernel and the name and version number of the distribution you're
1290 * the type of network device you're using.
1292 If you are having trouble capturing on a particular network interface,
1293 and you've made sure that (on platforms that require it) you've
1294 arranged that packet capture support is present, as per the above,
1295 first try capturing on that device with tcpdump.
1297 If you can capture on the interface with tcpdump, send mail to
1298 wireshark-users@wireshark.org giving full details of the problem,
1300 * the operating system you're using, and the version of that
1301 operating system (for Linux, give both the version number of the
1302 kernel and the name and version number of the distribution you're
1304 * the type of network device you're using;
1305 * the error message you get from Wireshark.
1307 If you cannot capture on the interface with tcpdump, this is almost
1308 certainly a problem with one or more of:
1309 * the operating system you're using;
1310 * the device driver for the interface you're using;
1311 * the libpcap library;
1313 so you should report the problem to the company or organization that
1314 produces the OS (in the case of a Linux distribution, report the
1315 problem to whoever produces the distribution).
1317 You may also want to ask the wireshark-users@wireshark.org and the
1318 tcpdump-workers@tcpdump.org mailing lists to see if anybody happens to
1319 know about the problem and know a workaround or fix for the problem. In
1320 your mail, please give full details of the problem, as described above,
1321 and also indicate that the problem occurs with tcpdump not just with
1324 Q 9.2: I'm running Wireshark on a UNIX-flavored OS; why do no network
1325 interfaces show up in the list of interfaces in the "Interface:" field
1326 in the dialog box popped up by "Capture->Start"?
1328 A: This is really the same question as the previous one; see the
1329 response to that question.
1331 Q 9.3: I'm capturing packets on Linux; why do the time stamps have only
1332 100ms resolution, rather than 1us resolution?
1334 A: Wireshark gets time stamps from libpcap/WinPcap, and libpcap/WinPcap
1335 get them from the OS kernel, so Wireshark - and any other program using
1336 libpcap, such as tcpdump - is at the mercy of the time stamping code in
1337 the OS for time stamps.
1339 At least on x86-based machines, Linux can get high-resolution time
1340 stamps on newer processors with the Time Stamp Counter (TSC) register;
1341 for example, Intel x86 processors, starting with the Pentium Pro, and
1342 including all x86 processors since then, have had a TSC, and other
1343 vendors probably added the TSC at some point to their families of x86
1346 The Linux kernel must be configured with the CONFIG_X86_TSC option
1347 enabled in order to use the TSC. Make sure this option is enabled in
1350 In addition, some Linux distributions may have bugs in their versions
1351 of the kernel that cause packets not to be given high-resolution time
1352 stamps even if the TSC is enabled. See, for example, bug 61111 for Red
1353 Hat Linux 7.2. If your distribution has a bug such as this, you may
1354 have to run a standard kernel from kernel.org in order to get
1355 high-resolution time stamps.
1357 10. Capturing packets on wireless LANs
1359 Q 10.1: How can I capture raw 802.11 frames, including non-data
1360 (management, beacon) frames?
1362 A: That depends on the operating system on which you're running, and on
1363 the 802.11 interface on which you're capturing.
1365 This would probably require that you capture in promiscuous mode or in
1366 the mode called "monitor mode" or "RFMON mode". On some platforms, or
1367 with some cards, this might require that you capture in monitor mode -
1368 promiscuous mode might not be sufficient. If you want to capture
1369 traffic on networks other than the one with which you're associated,
1370 you will have to capture in monitor mode.
1372 Not all operating systems support capturing non-data packets and, even
1373 on operating systems that do support it, not all drivers, and thus not
1374 all interfaces, support it. Even on those that do, monitor mode might
1375 not be supported by the operating system or by the drivers for all
1378 NOTE: an interface running in monitor mode will, on most if not all
1379 platforms, not be able to act as a regular network interface; putting
1380 it into monitor mode will, in effect, take your machine off of whatever
1381 network it's on as long as the interface is in monitor mode, allowing
1382 it only to passively capture packets.
1384 This means that you should disable name resolution when capturing in
1385 monitor mode; otherwise, when Wireshark (or TShark, or tcpdump) tries
1386 to display IP addresses as host names, it will probably block for a
1387 long time trying to resolve the name because it will not be able to
1388 communicate with any DNS or NIS servers.
1390 See the Wireshark Wiki item on 802.11 capturing for details.
1392 Q 10.2: How do I capture on an 802.11 device in monitor mode?
1394 A: Whether you will be able to capture in monitor mode depends on the
1395 operating system, adapter, and driver you're using. See the previous
1396 question for information on monitor mode, including a link to the
1397 Wireshark Wiki page that gives details on 802.11 capturing.
1401 Q 11.1: Why am I seeing lots of packets with incorrect TCP checksums?
1403 A: If the packets that have incorrect TCP checksums are all being sent
1404 by the machine on which Wireshark is running, this is probably because
1405 the network interface on which you're capturing does TCP checksum
1406 offloading. That means that the TCP checksum is added to the packet by
1407 the network interface, not by the OS's TCP/IP stack; when capturing on
1408 an interface, packets being sent by the host on which you're capturing
1409 are directly handed to the capture interface by the OS, which means
1410 that they are handed to the capture interface without a TCP checksum
1411 being added to them.
1413 The only way to prevent this from happening would be to disable TCP
1414 checksum offloading, but
1415 1. that might not even be possible on some OSes;
1416 2. that could reduce networking performance significantly.
1418 However, you can disable the check that Wireshark does of the TCP
1419 checksum, so that it won't report any packets as having TCP checksum
1420 errors, and so that it won't refuse to do TCP reassembly due to a
1421 packet having an incorrect TCP checksum. That can be set as an
1422 Wireshark preference by selecting "Preferences" from the "Edit" menu,
1423 opening up the "Protocols" list in the left-hand pane of the
1424 "Preferences" dialog box, selecting "TCP", from that list, turning off
1425 the "Check the validity of the TCP checksum when possible" option,
1426 clicking "Save" if you want to save that setting in your preference
1427 file, and clicking "OK".
1429 It can also be set on the Wireshark or TShark command line with a -o
1430 tcp.check_checksum:false command-line flag, or manually set in your
1431 preferences file by adding a tcp.check_checksum:false line.
1433 Q 11.2: I've just installed Wireshark, and the traffic on my local LAN
1434 is boring. Where can I find more interesting captures?
1436 A: We have a collection of strange and exotic sample capture files at
1437 http://wiki.wireshark.org/SampleCaptures
1439 Q 11.3: Why doesn't Wireshark correctly identify RTP packets? It shows
1442 A: Wireshark can identify a UDP datagram as containing a packet of a
1443 particular protocol running atop UDP only if
1444 1. The protocol in question has a particular standard port number, and
1445 the UDP source or destination port number is that port
1446 2. Packets of that protocol can be identified by looking for a
1447 "signature" of some type in the packet - i.e., some data that, if
1448 Wireshark finds it in some particular part of a packet, means that
1449 the packet is almost certainly a packet of that type.
1450 3. Some other traffic earlier in the capture indicated that, for
1451 example, UDP traffic between two particular addresses and ports
1452 will be RTP traffic.
1454 RTP doesn't have a standard port number, so 1) doesn't work; it
1455 doesn't, as far as I know, have any "signature", so 2) doesn't work.
1457 That leaves 3). If there's RTSP traffic that sets up an RTP session,
1458 then, at least in some cases, the RTSP dissector will set things up so
1459 that subsequent RTP traffic will be identified. Currently, that's the
1460 only place we do that; there may be other places.
1462 However, there will always be places where Wireshark is simply
1463 incapable of deducing that a given UDP flow is RTP; a mechanism would
1464 be needed to allow the user to specify that a given conversation should
1465 be treated as RTP. As of Wireshark 0.8.16, such a mechanism exists; if
1466 you select a UDP or TCP packet, the right mouse button menu will have a
1467 "Decode As..." menu item, which will pop up a dialog box letting you
1468 specify that the source port, the destination port, or both the source
1469 and destination ports of the packet should be dissected as some
1470 particular protocol.
1472 Q 11.4: Why doesn't Wireshark show Yahoo Messenger packets in captures
1473 that contain Yahoo Messenger traffic?
1475 A: Wireshark only recognizes as Yahoo Messenger traffic packets to or
1476 from TCP port 3050 that begin with "YPNS", "YHOO", or "YMSG". TCP
1477 segments that start with the middle of a Yahoo Messenger packet that
1478 takes more than one TCP segment will not be recognized as Yahoo
1479 Messenger packets (even if the TCP segment also contains the beginning
1480 of another Yahoo Messenger packet).
1482 12. Filtering traffic
1484 Q 12.1: I saved a filter and tried to use its name to filter the
1485 display; why do I get an "Unexpected end of filter string" error?
1487 A: You cannot use the name of a saved display filter as a filter. To
1488 filter the display, you can enter a display filter expression - not the
1489 name of a saved display filter - in the "Filter:" box at the bottom of
1490 the display, and type the key or press the "Apply" button (that does
1491 not require you to have a saved filter), or, if you want to use a saved
1492 filter, you can press the "Filter:" button, select the filter in the
1493 dialog box that pops up, and press the "OK" button.
1495 Q 12.2: How can I search for, or filter, packets that have a particular
1496 string anywhere in them?
1498 A: If you want to do this when capturing, you can't. That's a feature
1499 that would be hard to implement in capture filters without changes to
1500 the capture filter code, which, on many platforms, is in the OS kernel
1501 and, on other platforms, is in the libpcap library.
1503 In releases prior to 0.9.14, you also can't search for, or filter,
1504 packets containing a particular string even after you've captured them.
1506 In 0.9.14, you can search for, but not filter, packets that have a
1507 particular string; this has been added to the "Find Frame" dialog
1508 ("Find Frame" under the "Edit" menu, or control-F).
1510 In 0.9.15 and later, you can search for those packets using either the
1511 mechanism introduced in 0.9.14 or using the new "contains" operator in
1512 filter expressions, which lets you search the entire packet or text
1513 string or byte string fields in the packet; the "contains" operator can
1514 also be used in expressions used to filter the display.
1516 Q 12.3: How do I filter a capture to see traffic for virus XXX?
1518 A: For some viruses/worms there might be a capture filter to recognize
1519 the virus traffic. Check the CaptureFilters page on the Wireshark Wiki
1520 to see if anybody's added such a filter.
1522 Note that Wireshark was not designed to be an intrusion detection
1523 system; you might be able to use it as an IDS, but in most cases
1524 software designed to be an IDS, such as Snort or Prelude, will probably
1527 The Bleeding Edge of Snort has a collection of signatures for Snort to
1528 detect various viruses, worms, and the like.