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 What kind of shark is Wireshark?
22 1.5 How is Wireshark pronounced, spelled and capitalized?
24 1.6 How much does Wireshark cost?
26 1.7 Can I use Wireshark commercially?
28 1.8 Can I use Wireshark as part of my commercial product?
30 1.9 What protocols are currently supported?
32 1.10 Are there any plans to support {your favorite protocol}?
34 1.11 Can Wireshark read capture files from {your favorite network
37 1.12 What devices can Wireshark use to capture packets?
39 1.13 Does Wireshark work on Windows Vista?
41 2. Downloading Wireshark:
43 2.1 Why do I get an error when I try to run the Win32 installer?
45 3. Installing Wireshark:
47 3.1 I installed the Wireshark RPM (or other package); why did it
48 install TShark but not Wireshark?
50 4. Building Wireshark:
52 4.1 I have libpcap installed; why did the configure script not find
55 4.2 Why do I get the error
57 dftest_DEPENDENCIES was already defined in condition TRUE, which
58 implies condition HAVE_PLUGINS_TRUE
60 when I try to build Wireshark from SVN or a SVN snapshot?
62 4.3 Why does the linker fail with a number of "Output line too long."
63 messages followed by linker errors when I try to buil Wireshark?
65 4.4 When I try to build Wireshark on Solaris, why does the link fail
66 complaining that plugin_list is undefined?
68 4.5 When I try to build Wireshark on Windows, why does the build fail
69 because of conflicts between winsock.h and winsock2.h?
71 5. Starting Wireshark:
73 5.1 Why does Wireshark crash with a Bus Error when I try to run it on
76 5.2 When I run Wireshark on Windows NT, why does it die with a Dr.
77 Watson error, reporting an "Integer division by zero" exception, when I
80 5.3 When I try to run Wireshark, why does it complain about
81 sprint_realloc_objid being undefined?
83 5.4 I've installed Wireshark from Fink on Mac OS X; why is it very slow
86 6. Crashes and other fatal errors:
88 6.1 I have an XXX network card on my machine; if I try to capture on
89 it, why does my machine crash or reset itself?
91 6.2 Why does my machine crash or reset itself when I select "Start"
92 from the "Capture" menu or select "Preferences" from the "Edit" menu?
96 7.1 When I use Wireshark to capture packets, why do I see only packets
97 to and from my machine, or not see all the traffic I'm expecting to see
98 from or to the machine I'm trying to monitor?
100 7.2 When I capture with Wireshark, why can't I see any TCP packets
101 other than packets to and from my machine, even though another analyzer
102 on the network sees those packets?
104 7.3 Why am I only seeing ARP packets when I try to capture traffic?
106 7.4 Why am I not seeing any traffic when I try to capture traffic?
108 7.5 Can Wireshark capture on (my T1/E1 line, SS7 links, etc.)?
110 7.6 How do I put an interface into promiscuous mode?
112 7.7 I can set a display filter just fine; why don't capture filters
115 7.8 I'm entering valid capture filters; why do I still get "parse
118 7.9 How can I capture packets with CRC errors?
120 7.10 How can I capture entire frames, including the FCS?
122 7.11 I'm capturing packets on a machine on a VLAN; why don't the
123 packets I'm capturing have VLAN tags?
125 7.12 Why does Wireshark hang after I stop a capture?
127 8. Capturing packets on Windows:
129 8.1 I'm running Wireshark on Windows; why does some network interface
130 on my machine not show up in the list of interfaces in the "Interface:"
131 field in the dialog box popped up by "Capture->Start", and/or why does
132 Wireshark give me an error if I try to capture on that interface?
134 8.2 I'm running Wireshark on Windows; why do no network interfaces show
135 up in the list of interfaces in the "Interface:" field in the dialog
136 box popped up by "Capture->Start"?
138 8.3 I'm running Wireshark on Windows; why doesn't my serial port/ADSL
139 modem/ISDN modem show up in the list of interfaces in the "Interface:"
140 field in the dialog box popped up by "Capture->Start"?
142 8.4 I'm running Wireshark on Windows NT 4.0/Windows 2000/Windows
143 XP/Windows Server 2003; my machine has a PPP (dial-up POTS, ISDN, etc.)
144 interface, and it shows up in the "Interface" item in the "Capture
145 Options" dialog box. Why can no packets be sent on or received from
146 that network while I'm trying to capture traffic on that interface?
148 8.5 I'm running Wireshark on Windows; why am I not seeing any traffic
149 being sent by the machine running Wireshark?
151 8.6 When I capture on Windows in promiscuous mode, I can see packets
152 other than those sent to or from my machine; however, those packets
153 show up with a "Short Frame" indication, unlike packets to or from my
154 machine. What should I do to arrange that I see those packets in their
157 8.7 I'm trying to capture 802.11 traffic on Windows; why am I not
160 8.8 I'm trying to capture 802.11 traffic on Windows; why am I seeing
161 packets received by the machine on which I'm capturing traffic, but not
162 packets sent by that machine?
164 8.9 I'm trying to capture Ethernet VLAN traffic on Windows, and I'm
165 capturing on a "raw" Ethernet device rather than a "VLAN interface", so
166 that I can see the VLAN headers; why am I seeing packets received by
167 the machine on which I'm capturing traffic, but not packets sent by
170 9. Capturing packets on UN*Xes:
172 9.1 I'm running Wireshark on a UNIX-flavored OS; why does some network
173 interface on my machine not show up in the list of interfaces in the
174 "Interface:" field in the dialog box popped up by "Capture->Start",
175 and/or why does Wireshark give me an error if I try to capture on that
178 9.2 I'm running Wireshark on a UNIX-flavored OS; why do no network
179 interfaces show up in the list of interfaces in the "Interface:" field
180 in the dialog box popped up by "Capture->Start"?
182 9.3 I'm capturing packets on Linux; why do the time stamps have only
183 100ms resolution, rather than 1us resolution?
185 10. Capturing packets on wireless LANs:
187 10.1 How can I capture raw 802.11 frames, including non-data
188 (management, beacon) frames?
190 10.2 How do I capture on an 802.11 device in monitor mode?
194 11.1 Why am I seeing lots of packets with incorrect TCP checksums?
196 11.2 I've just installed Wireshark, and the traffic on my local LAN is
197 boring. Where can I find more interesting captures?
199 11.3 Why doesn't Wireshark correctly identify RTP packets? It shows
202 11.4 Why doesn't Wireshark show Yahoo Messenger packets in captures
203 that contain Yahoo Messenger traffic?
205 12. Filtering traffic:
207 12.1 I saved a filter and tried to use its name to filter the display;
208 why do I get an "Unexpected end of filter string" error?
210 12.2 How can I search for, or filter, packets that have a particular
211 string anywhere in them?
213 12.3 How do I filter a capture to see traffic for virus XXX?
217 Q 1.1: What is Wireshark?
219 A: Wireshark® is the world's most popular network protocol analyzer. It
220 has a rich and powerful feature set and runs on most computing
221 platforms including Windows, OS X, Linux, and UNIX. Network
222 professionals, security experts, developers, and educators around the
223 world use it regularly. It is freely available as open source, and is
224 released under the GNU General Public License version 2.
225 It is developed and maintained by a global team of protocol experts,
226 and it is an example of a disruptive technology.
227 Wireshark used to be known as Ethereal®. See the next question for
228 details about the name change. If you're still using Ethereal, it is
229 strongly recommended that you upgrade to Wireshark.
230 For more information, please see the About Wireshark page.
232 Q 1.2: What's up with the name change? Is Wireshark a fork?
234 A: In May of 2006, Gerald Combs (the original author of Ethereal) went
235 to work for CACE Technologies (best known for WinPcap). Unfortunately,
236 he had to leave the Ethereal trademarks behind.
237 This left the project in an awkward position. The only reasonable way
238 to ensure the continued success of the project was to change the name.
239 This is how Wireshark was born.
240 Wireshark is almost (but not quite) a fork. Normally a "fork" of an
241 open source project results in two names, web sites, development teams,
242 support infrastructures, etc. This is the case with Wireshark except
243 for one notable exception -- every member of the core development team
244 is now working on Wireshark. There has been no active development on
245 Ethereal since the name change. Several parts of the Ethereal web site
246 (such as the mailing lists, source code repository, and build farm)
248 More information on the name change can be found here:
251 * Many other articles in
253 Q 1.3: Where can I get help?
255 A: Community support is available on the wireshark-users mailing list.
256 Subscription information and archives for all of Wireshark's mailing
257 lists can be found at http://www.wireshark.org/mailman/listinfo. An IRC
258 channel dedicated to Wireshark can be found at
259 irc://irc.freenode.net/wireshark.
260 Self-paced and instructor-led training is available at Wireshark
261 University. A certification program will be announced in Q3 2007.
262 Commercial support and development services are available from CACE
265 Q 1.4: What kind of shark is Wireshark?
267 A: carcharodon photoshopia.
269 Q 1.5: How is Wireshark pronounced, spelled and capitalized?
271 A: Wireshark is pronounced as the word wire followed immediately by the
272 word shark. Exact pronunciation and emphasis may vary depending on your
273 locale (e.g. Arkansas).
274 It's spelled with a capital W, followed by a lower-case ireshark. It is
275 not a CamelCase word, i.e., WireShark is incorrect.
277 Q 1.6: How much does Wireshark cost?
279 A: Wireshark is "free software"; you can download it without paying any
280 license fee. The version of Wireshark you download isn't a "demo"
281 version, with limitations not present in a "full" version; it is the
283 The license under which Wireshark is issued is the GNU General Public
284 License. See the GNU GPL FAQ for some more information.
286 Q 1.7: Can I use Wireshark commercially?
288 A: Yes, if, for example, you mean "I work for a commercial
289 organization; can I use Wireshark to capture and analyze network
290 traffic in our company's networks or in our customer's networks?"
291 If you mean "Can I use Wireshark as part of my commercial product?",
292 see the next entry in the FAQ.
294 Q 1.8: Can I use Wireshark as part of my commercial product?
296 A: As noted, Wireshark is licensed under the GNU General Public
297 License. The GPL imposes conditions on your use of GPL'ed code in your
298 own products; you cannot, for example, make a "derived work" from
299 Wireshark, by making modifications to it, and then sell the resulting
300 derived work and not allow recipients to give away the resulting work.
301 You must also make the changes you've made to the Wireshark source
302 available to all recipients of your modified version; those changes
303 must also be licensed under the terms of the GPL. See the GPL FAQ for
304 more details; in particular, note the answer to the question about
305 modifying a GPLed program and selling it commercially, and the question
306 about linking GPLed code with other code to make a proprietary program.
307 You can combine a GPLed program such as Wireshark and a commercial
308 program as long as they communicate "at arm's length", as per this item
311 Q 1.9: What protocols are currently supported?
313 A: There are currently hundreds of supported protocols and media.
314 Details can be found in the wireshark(1) man page.
316 Q 1.10: Are there any plans to support {your favorite protocol}?
318 A: Support for particular protocols is added to Wireshark as a result
319 of people contributing that support; no formal plans for adding support
320 for particular protocols in particular future releases exist.
322 Q 1.11: Can Wireshark read capture files from {your favorite network
325 A: Support for particular protocols is added to Wireshark as a result
326 of people contributing that support; no formal plans for adding support
327 for particular protocols in particular future releases exist.
328 If a network analyzer writes out files in a format already supported by
329 Wireshark (e.g., in libpcap format), Wireshark may already be able to
330 read them, unless the analyzer has added its own proprietary extensions
332 If a network analyzer writes out files in its own format, or has added
333 proprietary extensions to another format, in order to make Wireshark
334 read captures from that network analyzer, we would either have to have
335 a specification for the file format, or the extensions, sufficient to
336 give us enough information to read the parts of the file relevant to
337 Wireshark, or would need at least one capture file in that format AND a
338 detailed textual analysis of the packets in that capture file (showing
339 packet time stamps, packet lengths, and the top-level packet header) in
340 order to reverse-engineer the file format.
341 Note that there is no guarantee that we will be able to
342 reverse-engineer a capture file format.
344 Q 1.12: What devices can Wireshark use to capture packets?
346 A: Wireshark can read live data from Ethernet, Token-Ring, FDDI, serial
347 (PPP and SLIP) (if the OS on which it's running allows Wireshark to do
348 so), 802.11 wireless LAN (if the OS on which it's running allows
349 Wireshark to do so), ATM connections (if the OS on which it's running
350 allows Wireshark to do so), and the "any" device supported on Linux by
351 recent versions of libpcap.
352 See the list of supported capture media on various OSes for details
353 (several items in there say "Unknown", which doesn't mean "Wireshark
354 can't capture on them", it means "we don't know whether it can capture
355 on them"; we expect that it will be able to capture on many of them,
356 but we haven't tried it ourselves - if you try one of those types and
357 it works, please update the wiki page accordingly.
358 It can also read a variety of capture file formats, including:
359 * AG Group/WildPackets EtherPeek/TokenPeek/AiroPeek/EtherHelp/Packet
361 * AIX's iptrace captures
362 * Accellent's 5Views LAN agent output
363 * Cinco Networks NetXRay captures
364 * Cisco Secure Intrusion Detection System IPLog output
365 * CoSine L2 debug output
366 * DBS Etherwatch VMS text output
367 * Endace Measurement Systems' ERF format captures
368 * EyeSDN USB S0 traces
369 * HP-UX nettl captures
370 * ISDN4BSD project i4btrace captures
371 * Linux Bluez Bluetooth stack hcidump -w traces
372 * Lucent/Ascend router debug output
373 * Microsoft Network Monitor captures
374 * Network Associates Windows-based Sniffer captures
375 * Network General/Network Associates DOS-based Sniffer (compressed or
376 uncompressed) captures
377 * Network Instruments Observer version 9 captures
378 * Novell LANalyzer captures
379 * RADCOM's WAN/LAN analyzer captures
380 * Shomiti/Finisar Surveyor captures
381 * Toshiba's ISDN routers dump output
382 * VMS TCPIPtrace/TCPtrace/UCX$TRACE output
383 * Visual Networks' Visual UpTime traffic capture
384 * libpcap, tcpdump and various other tools using tcpdump's capture
386 * snoop and atmsnoop output
388 so that it can read traces from various network types, as captured by
389 other applications or equipment, even if it cannot itself capture on
392 Q 1.13: Does Wireshark work on Windows Vista?
394 A: Yes, but if you want to capture packets, you must make sure npf.sys
395 is loaded. You can do this by selecting Start WinPcap service "NPF" at
396 startup in the installer or by running sc config npf start= auto as
397 Administrator from the command line. You can also run Wireshark as
398 Administrator, but this is discouraged. See the CaputrePrivileges page
399 on the wiki for more details.
401 2. Downloading Wireshark
403 Q 2.1: Why do I get an error when I try to run the Win32 installer?
405 A: The program you used to download it may have downloaded it
406 incorrectly. Web browsers and download accelerators sometimes may do
408 Try downloading it with, for example:
409 * Wget, for which Windows binaries are available from Christopher
410 Lewis or wGetGUI, which offers a GUI interface that uses wget;
411 * WS_FTP from Ipswitch,
412 * the ftp command that comes with Windows.
414 If you use the ftp command, make sure you do the transfer in binary
415 mode rather than ASCII mode, by using the binary command before
416 transferring the file.
418 3. Installing Wireshark
420 Q 3.1: I installed the Wireshark RPM (or other package); why did it
421 install TShark but not Wireshark?
423 A: Many distributions have separate Wireshark packages, one for non-GUI
424 components such as TShark, editcap, dumpcap, etc. and one for the GUI.
425 If this is the case on your system, there's probably a separate package
426 named wireshark-gnome or wireshark-gtk+. Find it and install it.
428 4. Building Wireshark
430 Q 4.1: I have libpcap installed; why did the configure script not find
433 A: Are you sure pcap.h and bpf.h are installed? The official
434 distribution of libpcap only installs the libpcap.a library file when
435 "make install" is run. To install pcap.h and bpf.h, you must run "make
436 install-incl". If you're running Debian or Redhat, make sure you have
437 the "libpcap-dev" or "libpcap-devel" packages installed.
438 It's also possible that pcap.h and bpf.h have been installed in a
439 strange location. If this is the case, you may have to tweak
442 Q 4.2: Why do I get the error
444 dftest_DEPENDENCIES was already defined in condition TRUE, which
445 implies condition HAVE_PLUGINS_TRUE
447 when I try to build Wireshark from SVN or a SVN snapshot?
449 A: You probably have automake 1.5 installed on your machine (the
450 command automake --version will report the version of automake on your
451 machine). There is a bug in that version of automake that causes this
452 problem; upgrade to a later version of automake (1.6 or later).
454 Q 4.3: Why does the linker fail with a number of "Output line too
455 long." messages followed by linker errors when I try to buil Wireshark?
457 A: The version of the sed command on your system is incapable of
458 handling very long lines. On Solaris, for example, /usr/bin/sed has a
459 line length limit too low to allow libtool to work; /usr/xpg4/bin/sed
460 can handle it, as can GNU sed if you have it installed.
461 On Solaris, changing your command search path to search /usr/xpg4/bin
462 before /usr/bin should make the problem go away; on any platform on
463 which you have this problem, installing GNU sed and changing your
464 command path to search the directory in which it is installed before
465 searching the directory with the version of sed that came with the OS
466 should make the problem go away.
468 Q 4.4: When I try to build Wireshark on Solaris, why does the link fail
469 complaining that plugin_list is undefined?
471 A: This appears to be due to a problem with some versions of the GTK+
472 and GLib packages from www.sunfreeware.org; un-install those packages,
473 and try getting the 1.2.10 versions from that site, or the versions
474 from The Written Word, or the versions from Sun's GNOME distribution,
475 or the versions from the supplemental software CD that comes with the
476 Solaris media kit, or build them from source from the GTK Web site.
477 Then re-run the configuration script, and try rebuilding Wireshark. (If
478 you get the 1.2.10 versions from www.sunfreeware.org, and the problem
479 persists, un-install them and try installing one of the other versions
482 Q 4.5: When I try to build Wireshark on Windows, why does the build
483 fail because of conflicts between winsock.h and winsock2.h?
485 A: As of Wireshark 0.9.5, you must install WinPcap 2.3 or later, and
486 the corresponding version of the developer's pack, in order to be able
487 to compile Wireshark; it will not compile with older versions of the
488 developer's pack. The symptoms of this failure are conflicts between
489 definitions in winsock.h and in winsock2.h; Wireshark uses winsock2.h,
490 but pre-2.3 versions of the WinPcap developer's packet use winsock.h.
491 (2.3 uses winsock2.h, so if Wireshark were to use winsock.h, it would
492 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.)
512 Similar problems may exist with older versions of GTK+ for earlier
515 Q 5.2: When I run Wireshark on Windows NT, why does it die with a Dr.
516 Watson error, reporting an "Integer division by zero" exception, when I
519 A: In at least some case, this appears to be due to using the default
520 VGA driver; if that's not the correct driver for your video card, try
521 running the correct driver for your video card.
523 Q 5.3: When I try to run Wireshark, why does it complain about
524 sprint_realloc_objid being undefined?
526 A: Wireshark can only be linked with version 4.2.2 or later of UCD
527 SNMP. Your version of Wireshark was dynamically linked with such a
528 version of UCD SNMP; however, you have an older version of UCD SNMP
529 installed, which means that when Wireshark is run, it tries to link to
530 the older version, and fails. You will have to replace that version of
531 UCD SNMP with version 4.2.2 or a later version.
533 Q 5.4: I've installed Wireshark from Fink on Mac OS X; why is it very
536 A: When an application is installed on OS X, prior to 10.4, it is
537 usually "prebound" to speed up launching the application. (That's what
538 the "Optimizing" phase of installation is.)
539 Fink normally performs prebinding automatically when you install a
540 package. However, in some rare cases, for whatever reason the
541 prebinding caches get corrupt, and then not only does prebinding fail,
542 but startup actually becomes much slower, because the system tries in
543 vain to perform prebinding "on the fly" as you launch the application.
544 This fails, causing sometimes huge delays.
545 To fix the prebinding caches, run the command
546 sudo /sw/var/lib/fink/prebound/update-package-prebinding.pl -f
548 6. Crashes and other fatal errors
550 Q 6.1: I have an XXX network card on my machine; if I try to capture on
551 it, why does my machine crash or reset itself?
553 A: This is almost certainly a problem with one or more of:
554 * the operating system you're using;
555 * the device driver for the interface you're using;
556 * the libpcap/WinPcap library and, if this is Windows, the WinPcap
560 * if you are using Windows, see the WinPcap support page - check the
561 "Submitting bugs" section;
562 * if you are using some Linux distribution, some version of BSD, or
563 some other UNIX-flavored OS, you should report the problem to the
564 company or organization that produces the OS (in the case of a
565 Linux distribution, report the problem to whoever produces the
568 Q 6.2: Why does my machine crash or reset itself when I select "Start"
569 from the "Capture" menu or select "Preferences" from the "Edit" menu?
571 A: Both of those operations cause Wireshark to try to build a list of
572 the interfaces that it can open; it does so by getting a list of
573 interfaces and trying to open them. There is probably an OS, driver,
574 or, for Windows, WinPcap bug that causes the system to crash when this
575 happens; see the previous question.
579 Q 7.1: When I use Wireshark to capture packets, why do I see only
580 packets to and from my machine, or not see all the traffic I'm
581 expecting to see from or to the machine I'm trying to monitor?
583 A: This might be because the interface on which you're capturing is
584 plugged into an Ethernet or Token Ring switch; on a switched network,
585 unicast traffic between two ports will not necessarily appear on other
586 ports - only broadcast and multicast traffic will be sent to all ports.
587 Note that even if your machine is plugged into a hub, the "hub" may be
588 a switched hub, in which case you're still on a switched network.
589 Note also that on the Linksys Web site, they say that their
590 auto-sensing hubs "broadcast the 10Mb packets to the port that operate
591 at 10Mb only and broadcast the 100Mb packets to the ports that operate
592 at 100Mb only", which would indicate that if you sniff on a 10Mb port,
593 you will not see traffic coming sent to a 100Mb port, and vice versa.
594 This problem has also been reported for Netgear dual-speed hubs, and
595 may exist for other "auto-sensing" or "dual-speed" hubs.
596 Some switches have the ability to replicate all traffic on all ports to
597 a single port so that you can plug your analyzer into that single port
598 to sniff all traffic. You would have to check the documentation for the
599 switch to see if this is possible and, if so, to see how to do this.
600 See the switch reference page on the Wireshark Wiki for information on
601 some switches. (Note that it's a Wiki, so you can update or fix that
602 information, or add additional information on those switches or
603 information on new switches, yourself.)
604 Note also that many firewall/NAT boxes have a switch built into them;
605 this includes many of the "cable/DSL router" boxes. If you have a box
606 of that sort, that has a switch with some number of Ethernet ports into
607 which you plug machines on your network, and another Ethernet port used
608 to connect to a cable or DSL modem, you can, at least, sniff traffic
609 between the machines on your network and the Internet by plugging the
610 Ethernet port on the router going to the modem, the Ethernet port on
611 the modem, and the machine on which you're running Wireshark into a hub
612 (make sure it's not a switching hub, and that, if it's a dual-speed
613 hub, all three of those ports are running at the same speed.
614 If your machine is not plugged into a switched network or a dual-speed
615 hub, or it is plugged into a switched network but the port is set up to
616 have all traffic replicated to it, the problem might be that the
617 network interface on which you're capturing doesn't support
618 "promiscuous" mode, or because your OS can't put the interface into
619 promiscuous mode. Normally, network interfaces supply to the host only:
620 * packets sent to one of that host's link-layer addresses;
622 * multicast packets sent to a multicast address that the host has
623 configured the interface to accept.
625 Most network interfaces can also be put in "promiscuous" mode, in which
626 they supply to the host all network packets they see. Wireshark will
627 try to put the interface on which it's capturing into promiscuous mode
628 unless the "Capture packets in promiscuous mode" option is turned off
629 in the "Capture Options" dialog box, and TShark will try to put the
630 interface on which it's capturing into promiscuous mode unless the -p
631 option was specified. However, some network interfaces don't support
632 promiscuous mode, and some OSes might not allow interfaces to be put
633 into promiscuous mode.
634 If the interface is not running in promiscuous mode, it won't see any
635 traffic that isn't intended to be seen by your machine. It will see
636 broadcast packets, and multicast packets sent to a multicast MAC
637 address the interface is set up to receive.
638 You should ask the vendor of your network interface whether it supports
639 promiscuous mode. If it does, you should ask whoever supplied the
640 driver for the interface (the vendor, or the supplier of the OS you're
641 running on your machine) whether it supports promiscuous mode with that
643 In the case of token ring interfaces, the drivers for some of them, on
644 Windows, may require you to enable promiscuous mode in order to capture
645 in promiscuous mode. See the Wireshark Wiki item on Token Ring
646 capturing for details.
647 In the case of wireless LAN interfaces, it appears that, when those
648 interfaces are promiscuously sniffing, they're running in a
649 significantly different mode from the mode that they run in when
650 they're just acting as network interfaces (to the extent that it would
651 be a significant effor for those drivers to support for promiscuously
652 sniffing and acting as regular network interfaces at the same time), so
653 it may be that Windows drivers for those interfaces don't support
656 Q 7.2: When I capture with Wireshark, why can't I see any TCP packets
657 other than packets to and from my machine, even though another analyzer
658 on the network sees those packets?
660 A: You're probably not seeing any packets other than unicast packets to
661 or from your machine, and broadcast and multicast packets; a switch
662 will normally send to a port only unicast traffic sent to the MAC
663 address for the interface on that port, and broadcast and multicast
664 traffic - it won't send to that port unicast traffic sent to a MAC
665 address for some other interface - and a network interface not in
666 promiscuous mode will receive only unicast traffic sent to the MAC
667 address for that interface, broadcast traffic, and multicast traffic
668 sent to a multicast MAC address the interface is set up to receive.
669 TCP doesn't use broadcast or multicast, so you will only see your own
670 TCP traffic, but UDP services may use broadcast or multicast so you'll
671 see some UDP traffic - however, this is not a problem with TCP traffic,
672 it's a problem with unicast traffic, as you also won't see all UDP
673 traffic between other machines.
674 I.e., this is probably the same question as this earlier one; see the
675 response to that question.
677 Q 7.3: Why am I only seeing ARP packets when I try to capture traffic?
679 A: You're probably on a switched network, and running Wireshark on a
680 machine that's not sending traffic to the switch and not being sent any
681 traffic from other machines on the switch. ARP packets are often
682 broadcast packets, which are sent to all switch ports.
683 I.e., this is probably the same question as this earlier one; see the
684 response to that question.
686 Q 7.4: Why am I not seeing any traffic when I try to capture traffic?
688 A: Is the machine running Wireshark sending out any traffic on the
689 network interface on which you're capturing, or receiving any traffic
690 on that network, or is there any broadcast traffic on the network or
691 multicast traffic to a multicast group to which the machine running
693 If not, this may just be a problem with promiscuous sniffing, either
694 due to running on a switched network or a dual-speed hub, or due to
695 problems with the interface not supporting promiscuous mode; see the
696 response to this earlier question.
697 Otherwise, on Windows, see the response to this question and, on a
698 UNIX-flavored OS, see the response to this question.
700 Q 7.5: Can Wireshark capture on (my T1/E1 line, SS7 links, etc.)?
702 A: Wireshark can only capture on devices supported by libpcap/WinPcap.
703 On most OSes, only devices that can act as network interfaces of the
704 type that support IP are supported as capture devices for
705 libpcap/WinPcap, although the device doesn't necessarily have to be
706 running as an IP interface in order to support traffic capture.
707 On Linux and FreeBSD, libpcap 0.8 and later support the API for Endace
708 Measurement Systems' DAG cards, so that a system with one of those
709 cards, and its driver and libraries, installed can capture traffic with
710 those cards with libpcap-based applications. You would either have to
711 have a version of Wireshark built with that version of libpcap, or a
712 dynamically-linked version of Wireshark and a shared libpcap library
713 with DAG support, in order to do so with Wireshark. You should ask
714 Endace whether that could be used to capture traffic on, for example,
716 See the SS7 capture setup page on the Wireshark Wiki for current
717 information on capturing SS7 traffic on TDM links.
719 Q 7.6: How do I put an interface into promiscuous mode?
721 A: By not disabling promiscuous mode when running Wireshark or TShark.
723 * the form of promiscuous mode that libpcap (the library that
724 programs such as tcpdump, Wireshark, etc. use to do packet capture)
725 turns on will not necessarily be shown if you run ifconfig on the
726 interface on a UNIX system;
727 * some network interfaces might not support promiscuous mode, and
728 some drivers might not allow promiscuous mode to be turned on - see
729 this earlier question for more information on that;
730 * the fact that you're not seeing any traffic, or are only seeing
731 broadcast traffic, or aren't seeing any non-broadcast traffic other
732 than traffic to or from the machine running Wireshark, does not
733 mean that promiscuous mode isn't on - see this earlier question for
734 more information on that.
736 I.e., this is probably the same question as this earlier one; see the
737 response to that question.
739 Q 7.7: I can set a display filter just fine; why don't capture filters
742 A: Capture filters currently use a different syntax than display
743 filters. Here's the corresponding section from the wireshark(1) man
745 "Display filters in Wireshark are very powerful; more fields are
746 filterable in Wireshark than in other protocol analyzers, and the
747 syntax you can use to create your filters is richer. As Wireshark
748 progresses, expect more and more protocol fields to be allowed in
750 Packet capturing is performed with the pcap library. The capture filter
751 syntax follows the rules of the pcap library. This syntax is different
752 from the display filter syntax."
753 The capture filter syntax used by libpcap can be found in the
756 Q 7.8: I'm entering valid capture filters; why do I still get "parse
759 A: There is a bug in some versions of libpcap/WinPcap that cause it to
760 report parse errors even for valid expressions if a previous filter
761 expression was invalid and got a parse error.
762 Try exiting and restarting Wireshark; if you are using a version of
763 libpcap/WinPcap with this bug, this will "erase" its memory of the
764 previous parse error. If the capture filter that got the "parse error"
765 now works, the earlier error with that filter was probably due to this
767 The bug was fixed in libpcap 0.6; 0.4[.x] and 0.5[.x] versions of
768 libpcap have this bug, but 0.6[.x] and later versions don't.
769 Versions of WinPcap prior to 2.3 are based on pre-0.6 versions of
770 libpcap, and have this bug; WinPcap 2.3 is based on libpcap 0.6.2, and
771 doesn't have this bug.
772 If you are running Wireshark on a UNIX-flavored platform, run
773 "wireshark -v", or select "About Wireshark..." from the "Help" menu in
774 Wireshark, to see what version of libpcap it's using. If it's not 0.6
775 or later, you will need either to upgrade your OS to get a later
776 version of libpcap, or will need to build and install a later version
777 of libpcap from the tcpdump.org Web site and then recompile Wireshark
778 from source with that later version of libpcap.
779 If you are running Wireshark on Windows with a pre-2.3 version of
780 WinPcap, you will need to un-install WinPcap and then download and
783 Q 7.9: How can I capture packets with CRC errors?
785 A: Wireshark can capture only the packets that the packet capture
786 library - libpcap on UNIX-flavored OSes, and the WinPcap port to
787 Windows of libpcap on Windows - can capture, and libpcap/WinPcap can
788 capture only the packets that the OS's raw packet capture mechanism (or
789 the WinPcap driver, and the underlying OS networking code and network
790 interface drivers, on Windows) will allow it to capture.
791 Unless the OS always supplies packets with errors such as invalid CRCs
792 to the raw packet capture mechanism, or can be configured to do so,
793 invalid CRCs to the raw packet capture mechanism, Wireshark - and other
794 programs that capture raw packets, such as tcpdump - cannot capture
795 those packets. You will have to determine whether your OS needs to be
796 so configured and, if so, can be so configured, configure it if
797 necessary and possible, and make whatever changes to libpcap and the
798 packet capture program you're using are necessary, if any, to support
799 capturing those packets.
800 Most OSes probably do not support capturing packets with invalid CRCs
801 on Ethernet, and probably do not support it on most other link-layer
802 types. Some drivers on some OSes do support it, such as some Ethernet
803 drivers on FreeBSD; in those OSes, you might always get those packets,
804 or you might only get them if you capture in promiscuous mode (you'd
805 have to determine which is the case).
806 Note that libpcap does not currently supply to programs that use it an
807 indication of whether the packet's CRC was invalid (because the drivers
808 themselves do not supply that information to the raw packet capture
809 mechanism); therefore, Wireshark will not indicate which packets had
810 CRC errors unless the FCS was captured (see the next question) and
811 you're using Wireshark 0.9.15 and later, in which case Wireshark will
812 check the CRC and indicate whether it's correct or not.
814 Q 7.10: How can I capture entire frames, including the FCS?
816 A: Wireshark can only capture data that the packet capture library -
817 libpcap on UNIX-flavored OSes, and the WinPcap port to Windows of
818 libpcap on Windows - can capture, and libpcap/WinPcap can capture only
819 the data that the OS's raw packet capture mechanism (or the WinPcap
820 driver, and the underlying OS networking code and network interface
821 drivers, on Windows) will allow it to capture.
822 For any particular link-layer network type, unless the OS supplies the
823 FCS of a frame as part of the frame, or can be configured to do so,
824 Wireshark - and other programs that capture raw packets, such as
825 tcpdump - cannot capture the FCS of a frame. You will have to determine
826 whether your OS needs to be so configured and, if so, can be so
827 configured, configure it if necessary and possible, and make whatever
828 changes to libpcap and the packet capture program you're using are
829 necessary, if any, to support capturing the FCS of a frame.
830 Most OSes do not support capturing the FCS of a frame on Ethernet, and
831 probably do not support it on most other link-layer types. Some drivres
832 on some OSes do support it, such as some (all?) Ethernet drivers on
833 NetBSD and possibly the driver for Apple's gigabit Ethernet interface
834 in Mac OS X; in those OSes, you might always get the FCS, or you might
835 only get the FCS if you capture in promiscuous mode (you'd have to
836 determine which is the case).
837 Versions of Wireshark prior to 0.9.15 will not treat an Ethernet FCS in
838 a captured packet as an FCS. 0.9.15 and later will attempt to determine
839 whether there's an FCS at the end of the frame and, if it thinks there
840 is, will display it as such, and will check whether it's the correct
843 Q 7.11: I'm capturing packets on a machine on a VLAN; why don't the
844 packets I'm capturing have VLAN tags?
846 A: You might be capturing on what might be called a "VLAN interface" -
847 the way a particular OS makes VLANs plug into the networking stack
848 might, for example, be to have a network device object for the physical
849 interface, which takes VLAN packets, strips off the VLAN header and
850 constructs an Ethernet header, and passes that packet to an internal
851 network device object for the VLAN, which then passes the packets onto
852 various higher-level protocol implementations.
853 In order to see the raw Ethernet packets, rather than "de-VLANized"
854 packets, you would have to capture not on the virtual interface for the
855 VLAN, but on the interface corresponding to the physical network
856 device, if possible. See the Wireshark Wiki item on VLAN capturing for
859 Q 7.12: Why does Wireshark hang after I stop a capture?
861 A: The most likely reason for this is that Wireshark is trying to look
862 up an IP address in the capture to convert it to a name (so that, for
863 example, it can display the name in the source address or destination
864 address columns), and that lookup process is taking a very long time.
865 Wireshark calls a routine in the OS of the machine on which it's
866 running to convert of IP addresses to the corresponding names. That
867 routine probably does one or more of:
868 * a search of a system file listing IP addresses and names;
869 * a lookup using DNS;
870 * on UNIX systems, a lookup using NIS;
871 * on Windows systems, a NetBIOS-over-TCP query.
873 If a DNS server that's used in an address lookup is not responding, the
874 lookup will fail, but will only fail after a timeout while the system
875 routine waits for a reply.
876 In addition, on Windows systems, if the DNS lookup of the address
877 fails, either because the server isn't responding or because there are
878 no records in the DNS that could be used to map the address to a name,
879 a NetBIOS-over-TCP query will be made. That query involves sending a
880 message to the NetBIOS-over-TCP name service on that machine, asking
881 for the name and other information about the machine. If the machine
882 isn't running software that responds to those queries - for example,
883 many non-Windows machines wouldn't be running that software - the
884 lookup will only fail after a timeout. Those timeouts can cause the
885 lookup to take a long time.
886 If you disable network address-to-name translation - for example, by
887 turning off the "Enable network name resolution" option in the "Capture
888 Options" dialog box for starting a network capture - the lookups of the
889 address won't be done, which may speed up the process of reading the
890 capture file after the capture is stopped. You can make that setting
891 the default by selecting "Preferences" from the "Edit" menu, turning
892 off the "Enable network name resolution" option in the "Name
893 resolution" options in the preferences disalog box, and using the
894 "Save" button in that dialog box; note that this will save all your
895 current preference settings.
896 If Wireshark hangs when reading a capture even with network name
897 resolution turned off, there might, for example, be a bug in one of
898 Wireshark's dissectors for a protocol causing it to loop infinitely. If
899 you're not running the most recent release of Wireshark, you should
900 first upgrade to that release, as, if there's a bug of that sort, it
901 might've been fixed in a release after the one you're running. If the
902 hang occurs in the most recent release of Wireshark, the bug should be
903 reported to the Wireshark developers' mailing list at
904 wireshark-dev@wireshark.org.
905 On UNIX-flavored OSes, please try to force Wireshark to dump core, by
906 sending it a SIGABRT signal (usually signal 6) with the kill command,
907 and then get a stack trace if you have a debugger installed. A stack
908 trace can be obtained by using your debugger (gdb in this example), the
909 Wireshark binary, and the resulting core file. Here's an example of how
910 to use the gdb command backtrace to do so.
913 ..... prints the stack trace
917 The core dump file may be named "wireshark.core" rather than "core" on
918 some platforms (e.g., BSD systems).
919 Also, if at all possible, please send a copy of the capture file that
920 caused the problem; when capturing packets, Wireshark normally writes
921 captured packets to a temporary file, which will probably be in /tmp or
922 /var/tmp on UNIX-flavored OSes, \TEMP on the main system disk (normally
923 C:) on Windows 9x/Me/NT 4.0, and \Documents and Settings\your login
924 name\Local Settings\Temp on the main system disk on Windows
925 2000/Windows XP/Windows Server 2003, so the capture file will probably
926 be there. It will have a name beginning with ether, with some mixture
927 of letters and numbers after that. Please don't send a trace file
928 greater than 1 MB when compressed; instead, make it available via FTP
929 or HTTP, or say it's available but leave it up to a developer to ask
930 for it. If the trace file contains sensitive information (e.g.,
931 passwords), then please do not send it.
933 8. Capturing packets on Windows
935 Q 8.1: I'm running Wireshark on Windows; why does some network
936 interface on my machine not show up in the list of interfaces in the
937 "Interface:" field in the dialog box popped up by "Capture->Start",
938 and/or why does Wireshark give me an error if I try to capture on that
941 A: If you are running Wireshark on Windows NT 4.0, Windows 2000,
942 Windows XP, or Windows Server 2003, and this is the first time you have
943 run a WinPcap-based program (such as Wireshark, or TShark, or WinDump,
944 or Analyzer, or...) since the machine was rebooted, you need to run
945 that program from an account with administrator privileges; once you
946 have run such a program, you will not need administrator privileges to
947 run any such programs until you reboot.
948 If you are running on Windows Windows 2000/Windows XP/Windows Server
949 2003 and have administrator privileges or a WinPcap-based program has
950 been run with those privileges since the machine rebooted, this problem
951 might clear up if you completely un-install WinPcap and then re-install
953 If that doesn't work, then note that Wireshark relies on the WinPcap
954 library, on the WinPcap device driver, and on the facilities that come
955 with the OS on which it's running in order to do captures.
956 Therefore, if the OS, the WinPcap library, or the WinPcap driver don't
957 support capturing on a particular network interface device, Wireshark
958 won't be able to capture on that device.
960 1. 2.02 and earlier versions of the WinPcap driver and library that
961 Wireshark uses for packet capture didn't support Token Ring
962 interfaces; versions 2.1 and later support Token Ring, and the
963 current version of Wireshark works with (and, in fact, requires)
964 WinPcap 2.1 or later.
965 If you are having problems capturing on Token Ring interfaces, and
966 you have WinPcap 2.02 or an earlier version of WinPcap installed,
967 you should uninstall WinPcap, download and install the current
968 version of WinPcap, and then install the latest version of
970 2. WinPcap 2.3 has problems supporting PPP WAN interfaces on Windows
971 NT 4.0, Windows 2000, Windows XP, and Windows Server 2003, and, to
972 avoid those problems, support for PPP WAN interfaces on those
973 versions of Windows has been disabled in WinPcap 3.0. Regular
974 dial-up lines, ISDN lines, ADSL connections using PPPoE or PPPoA,
975 and various other lines such as T1/E1 lines are all PPP interfaces,
976 so those interfaces might not show up on the list of interfaces in
977 the "Capture Options" dialog on those OSes.
978 On Windows 2000, Windows XP, and Windows Server 2003, but not
979 Windows NT 4.0 or Windows Vista Beta 1, you should be able to
980 capture on the "GenericDialupAdapter" with WinPcap 3.1. (3.1 beta
981 releases called it the "NdisWanAdapter"; if you're using a 3.1 beta
982 release, you should un-install it and install the final 3.1
983 release.) See the Wireshark Wiki item on PPP capturing for details.
984 3. WinPcap prior to 3.0 does not support multiprocessor machines (note
985 that machines with a single multi-threaded processor, such as
986 Intel's new multi-threaded x86 processors, are multiprocessor
987 machines as far as the OS and WinPcap are concerned), and recent
988 2.x versions of WinPcap refuse to operate if they detect that
989 they're running on a multiprocessor machine, which means that they
990 may not show any network interfaces. You will need to use WinPcap
991 3.0 to capture on a multiprocessor machine.
993 If an interface doesn't show up in the list of interfaces in the
994 "Interface:" field, and you know the name of the interface, try
995 entering that name in the "Interface:" field and capturing on that
997 If the attempt to capture on it succeeds, the interface is somehow not
998 being reported by the mechanism Wireshark uses to get a list of
999 interfaces. Try listing the interfaces with WinDump; see the WinDump
1000 Web site for information on using WinDump.
1001 You would run WinDump with the -D flag; if it lists the interface,
1002 please report this to wireshark-dev@wireshark.org giving full details
1003 of the problem, including
1004 * the operating system you're using, and the version of that
1006 * the type of network device you're using;
1007 * the output of WinDump.
1009 If WinDump does not list the interface, this is almost certainly a
1010 problem with one or more of:
1011 * the operating system you're using;
1012 * the device driver for the interface you're using;
1013 * the WinPcap library and/or the WinPcap device driver;
1015 so first check the WinPcap FAQ or the Wiretapped.net mirror of that
1016 FAQ, to see if your problem is mentioned there. If not, then see the
1017 WinPcap support page - check the "Submitting bugs" section.
1018 If you are having trouble capturing on a particular network interface,
1019 first try capturing on that device with WinDump; see the WinDump Web
1020 site for information on using WinDump.
1021 If you can capture on the interface with WinDump, send mail to
1022 wireshark-users@wireshark.org giving full details of the problem,
1024 * the operating system you're using, and the version of that
1026 * the type of network device you're using;
1027 * the error message you get from Wireshark.
1029 If you cannot capture on the interface with WinDump, this is almost
1030 certainly a problem with one or more of:
1031 * the operating system you're using;
1032 * the device driver for the interface you're using;
1033 * the WinPcap library and/or the WinPcap device driver;
1035 so first check the WinPcap FAQ or the Wiretapped.net mirror of that
1036 FAQ, to see if your problem is mentioned there. If not, then see the
1037 WinPcap support page - check the "Submitting bugs" section.
1038 You may also want to ask the wireshark-users@wireshark.org and the
1039 winpcap-users@winpcap.org mailing lists to see if anybody happens to
1040 know about the problem and know a workaround or fix for the problem.
1041 (Note that you will have to subscribe to that list in order to be
1042 allowed to mail to it; see the WinPcap support page for information on
1043 the mailing list.) In your mail, please give full details of the
1044 problem, as described above, and also indicate that the problem occurs
1045 with WinDump, not just with Wireshark.
1047 Q 8.2: I'm running Wireshark on Windows; why do no network interfaces
1048 show up in the list of interfaces in the "Interface:" field in the
1049 dialog box popped up by "Capture->Start"?
1051 A: This is really the same question as a previous one; see the response
1054 Q 8.3: I'm running Wireshark on Windows; why doesn't my serial
1055 port/ADSL modem/ISDN modem show up in the list of interfaces in the
1056 "Interface:" field in the dialog box popped up by "Capture->Start"?
1058 A: Internet access on those devices is often done with the
1059 Point-to-Point (PPP) protocol; WinPcap 2.3 has problems supporting PPP
1060 WAN interfaces on Windows NT 4.0, Windows 2000, Windows XP, and Windows
1061 Server 2003, and, to avoid those problems, support for PPP WAN
1062 interfaces on those versions of Windows has been disabled in WinPcap
1064 On Windows 2000, Windows XP, and Windows Server 2003, but not Windows
1065 NT 4.0 or Windows Vista Beta 1, you should be able to capture on the
1066 "GenericDialupAdapter" with WinPcap 3.1. (3.1 beta releases called it
1067 the "NdisWanAdapter"; if you're using a 3.1 beta release, you should
1068 un-install it and install the final 3.1 release.) See the Wireshark
1069 Wiki item on PPP capturing for details.
1071 Q 8.4: I'm running Wireshark on Windows NT 4.0/Windows 2000/Windows
1072 XP/Windows Server 2003; my machine has a PPP (dial-up POTS, ISDN, etc.)
1073 interface, and it shows up in the "Interface" item in the "Capture
1074 Options" dialog box. Why can no packets be sent on or received from
1075 that network while I'm trying to capture traffic on that interface?
1077 A: Some versions of WinPcap have problems with PPP WAN interfaces on
1078 Windows NT 4.0, Windows 2000, Windows XP, and Windows Server 2003; one
1079 symptom that may be seen is that attempts to capture in promiscuous
1080 mode on the interface cause the interface to be incapable of sending or
1081 receiving packets. You can disable promiscuous mode using the -p
1082 command-line flag or the item in the "Capture Preferences" dialog box,
1083 but this may mean that outgoing packets, or incoming packets, won't be
1084 seen in the capture.
1085 On Windows 2000, Windows XP, and Windows Server 2003, but not Windows
1086 NT 4.0 or Windows Vista Beta 1, you should be able to capture on the
1087 "GenericDialupAdapter" with WinPcap 3.1. (3.1 beta releases called it
1088 the "NdisWanAdapter"; if you're using a 3.1 beta release, you should
1089 un-install it and install the final 3.1 release.) See the Wireshark
1090 Wiki item on PPP capturing for details.
1092 Q 8.5: I'm running Wireshark on Windows; why am I not seeing any
1093 traffic being sent by the machine running Wireshark?
1095 A: If you are running some form of VPN client software, it might be
1096 causing this problem; people have seen this problem when they have
1097 Check Point's VPN software installed on their machine. If that's the
1098 cause of the problem, you will have to remove the VPN software in order
1099 to have Wireshark (or any other application using WinPcap) see outgoing
1100 packets; unfortunately, neither we nor the WinPcap developers know any
1101 way to make WinPcap and the VPN software work well together.
1102 Also, some drivers for Windows (especially some wireless network
1103 interface drivers) apparently do not, when running in promiscuous mode,
1104 arrange that outgoing packets are delivered to the software that
1105 requested that the interface run promiscuously; try turning promiscuous
1108 Q 8.6: When I capture on Windows in promiscuous mode, I can see packets
1109 other than those sent to or from my machine; however, those packets
1110 show up with a "Short Frame" indication, unlike packets to or from my
1111 machine. What should I do to arrange that I see those packets in their
1114 A: In at least some cases, this appears to be the result of PGPnet
1115 running on the network interface on which you're capturing; turn it off
1118 Q 8.7: I'm trying to capture 802.11 traffic on Windows; why am I not
1121 A: At least some 802.11 card drivers on Windows appear not to see any
1122 packets if they're running in promiscuous mode. Try turning promiscuous
1123 mode off; you'll only be able to see packets sent by and received by
1124 your machine, not third-party traffic, and it'll look like Ethernet
1125 traffic and won't include any management or control frames, but that's
1126 a limitation of the card drivers.
1127 See MicroLogix's list of cards supported with WinPcap for information
1128 on support of various adapters and drivers with WinPcap.
1130 Q 8.8: I'm trying to capture 802.11 traffic on Windows; why am I seeing
1131 packets received by the machine on which I'm capturing traffic, but not
1132 packets sent by that machine?
1134 A: This appears to be another problem with promiscuous mode; try
1137 Q 8.9: I'm trying to capture Ethernet VLAN traffic on Windows, and I'm
1138 capturing on a "raw" Ethernet device rather than a "VLAN interface", so
1139 that I can see the VLAN headers; why am I seeing packets received by
1140 the machine on which I'm capturing traffic, but not packets sent by
1143 A: The way the Windows networking code works probably means that
1144 packets are sent on a "VLAN interface" rather than the "raw" device, so
1145 packets sent by the machine will only be seen when you capture on the
1146 "VLAN interface". If so, you will be unable to see outgoing packets
1147 when capturing on the "raw" device, so you are stuck with a choice
1148 between seeing VLAN headers and seeing outgoing packets.
1150 9. Capturing packets on UN*Xes
1152 Q 9.1: I'm running Wireshark on a UNIX-flavored OS; why does some
1153 network interface on my machine not show up in the list of interfaces
1154 in the "Interface:" field in the dialog box popped up by
1155 "Capture->Start", and/or why does Wireshark give me an error if I try
1156 to capture on that interface?
1158 A: You may need to run Wireshark from an account with sufficient
1159 privileges to capture packets, such as the super-user account, or may
1160 need to give your account sufficient privileges to capture packets.
1161 Only those interfaces that Wireshark can open for capturing show up in
1162 that list; if you don't have sufficient privileges to capture on any
1163 interfaces, no interfaces will show up in the list. See the Wireshark
1164 Wiki item on capture privileges for details on how to give a particular
1165 account or account group capture privileges on platforms where that can
1167 If you are running Wireshark from an account with sufficient
1168 privileges, then note that Wireshark relies on the libpcap library, and
1169 on the facilities that come with the OS on which it's running in order
1170 to do captures. On some OSes, those facilities aren't present by
1171 default; see the Wireshark Wiki item on adding capture support for
1173 And, even if you're running with an account that has sufficient
1174 privileges to capture, and capture support is present in your OS, if
1175 the OS or the libpcap library don't support capturing on a particular
1176 network interface device or particular types of devices, Wireshark
1177 won't be able to capture on that device.
1178 On Solaris, note that libpcap 0.6.2 and earlier didn't support Token
1179 Ring interfaces; the current version, 0.7.2, does support Token Ring,
1180 and the current version of Wireshark works with libpcap 0.7.2 and
1182 If an interface doesn't show up in the list of interfaces in the
1183 "Interface:" field, and you know the name of the interface, try
1184 entering that name in the "Interface:" field and capturing on that
1186 If the attempt to capture on it succeeds, the interface is somehow not
1187 being reported by the mechanism Wireshark uses to get a list of
1188 interfaces; please report this to wireshark-dev@wireshark.org giving
1189 full details of the problem, including
1190 * the operating system you're using, and the version of that
1191 operating system (for Linux, give both the version number of the
1192 kernel and the name and version number of the distribution you're
1194 * the type of network device you're using.
1196 If you are having trouble capturing on a particular network interface,
1197 and you've made sure that (on platforms that require it) you've
1198 arranged that packet capture support is present, as per the above,
1199 first try capturing on that device with tcpdump.
1200 If you can capture on the interface with tcpdump, send mail to
1201 wireshark-users@wireshark.org giving full details of the problem,
1203 * the operating system you're using, and the version of that
1204 operating system (for Linux, give both the version number of the
1205 kernel and the name and version number of the distribution you're
1207 * the type of network device you're using;
1208 * the error message you get from Wireshark.
1210 If you cannot capture on the interface with tcpdump, this is almost
1211 certainly a problem with one or more of:
1212 * the operating system you're using;
1213 * the device driver for the interface you're using;
1214 * the libpcap library;
1216 so you should report the problem to the company or organization that
1217 produces the OS (in the case of a Linux distribution, report the
1218 problem to whoever produces the distribution).
1219 You may also want to ask the wireshark-users@wireshark.org and the
1220 tcpdump-workers@tcpdump.org mailing lists to see if anybody happens to
1221 know about the problem and know a workaround or fix for the problem. In
1222 your mail, please give full details of the problem, as described above,
1223 and also indicate that the problem occurs with tcpdump not just with
1226 Q 9.2: I'm running Wireshark on a UNIX-flavored OS; why do no network
1227 interfaces show up in the list of interfaces in the "Interface:" field
1228 in the dialog box popped up by "Capture->Start"?
1230 A: This is really the same question as the previous one; see the
1231 response to that question.
1233 Q 9.3: I'm capturing packets on Linux; why do the time stamps have only
1234 100ms resolution, rather than 1us resolution?
1236 A: Wireshark gets time stamps from libpcap/WinPcap, and libpcap/WinPcap
1237 get them from the OS kernel, so Wireshark - and any other program using
1238 libpcap, such as tcpdump - is at the mercy of the time stamping code in
1239 the OS for time stamps.
1240 At least on x86-based machines, Linux can get high-resolution time
1241 stamps on newer processors with the Time Stamp Counter (TSC) register;
1242 for example, Intel x86 processors, starting with the Pentium Pro, and
1243 including all x86 processors since then, have had a TSC, and other
1244 vendors probably added the TSC at some point to their families of x86
1245 processors. The Linux kernel must be configured with the CONFIG_X86_TSC
1246 option enabled in order to use the TSC. Make sure this option is
1247 enabled in your kernel.
1248 In addition, some Linux distributions may have bugs in their versions
1249 of the kernel that cause packets not to be given high-resolution time
1250 stamps even if the TSC is enabled. See, for example, bug 61111 for Red
1251 Hat Linux 7.2. If your distribution has a bug such as this, you may
1252 have to run a standard kernel from kernel.org in order to get
1253 high-resolution time stamps.
1255 10. Capturing packets on wireless LANs
1257 Q 10.1: How can I capture raw 802.11 frames, including non-data
1258 (management, beacon) frames?
1260 A: That depends on the operating system on which you're running, and on
1261 the 802.11 interface on which you're capturing.
1262 This would probably require that you capture in promiscuous mode or in
1263 the mode called "monitor mode" or "RFMON mode". On some platforms, or
1264 with some cards, this might require that you capture in monitor mode -
1265 promiscuous mode might not be sufficient. If you want to capture
1266 traffic on networks other than the one with which you're associated,
1267 you will have to capture in monitor mode.
1268 Not all operating systems support capturing non-data packets and, even
1269 on operating systems that do support it, not all drivers, and thus not
1270 all interfaces, support it. Even on those that do, monitor mode might
1271 not be supported by the operating system or by the drivers for all
1273 NOTE: an interface running in monitor mode will, on most if not all
1274 platforms, not be able to act as a regular network interface; putting
1275 it into monitor mode will, in effect, take your machine off of whatever
1276 network it's on as long as the interface is in monitor mode, allowing
1277 it only to passively capture packets.
1278 This means that you should disable name resolution when capturing in
1279 monitor mode; otherwise, when Wireshark (or TShark, or tcpdump) tries
1280 to display IP addresses as host names, it will probably block for a
1281 long time trying to resolve the name because it will not be able to
1282 communicate with any DNS or NIS servers.
1283 See the Wireshark Wiki item on 802.11 capturing for details.
1285 Q 10.2: How do I capture on an 802.11 device in monitor mode?
1287 A: Whether you will be able to capture in monitor mode depends on the
1288 operating system, adapter, and driver you're using. See the previous
1289 question for information on monitor mode, including a link to the
1290 Wireshark Wiki page that gives details on 802.11 capturing.
1294 Q 11.1: Why am I seeing lots of packets with incorrect TCP checksums?
1296 A: If the packets that have incorrect TCP checksums are all being sent
1297 by the machine on which Wireshark is running, this is probably because
1298 the network interface on which you're capturing does TCP checksum
1299 offloading. That means that the TCP checksum is added to the packet by
1300 the network interface, not by the OS's TCP/IP stack; when capturing on
1301 an interface, packets being sent by the host on which you're capturing
1302 are directly handed to the capture interface by the OS, which means
1303 that they are handed to the capture interface without a TCP checksum
1304 being added to them.
1305 The only way to prevent this from happening would be to disable TCP
1306 checksum offloading, but
1307 1. that might not even be possible on some OSes;
1308 2. that could reduce networking performance significantly.
1310 However, you can disable the check that Wireshark does of the TCP
1311 checksum, so that it won't report any packets as having TCP checksum
1312 errors, and so that it won't refuse to do TCP reassembly due to a
1313 packet having an incorrect TCP checksum. That can be set as an
1314 Wireshark preference by selecting "Preferences" from the "Edit" menu,
1315 opening up the "Protocols" list in the left-hand pane of the
1316 "Preferences" dialog box, selecting "TCP", from that list, turning off
1317 the "Check the validity of the TCP checksum when possible" option,
1318 clicking "Save" if you want to save that setting in your preference
1319 file, and clicking "OK".
1320 It can also be set on the Wireshark or TShark command line with a -o
1321 tcp.check_checksum:false command-line flag, or manually set in your
1322 preferences file by adding a tcp.check_checksum:false line.
1324 Q 11.2: I've just installed Wireshark, and the traffic on my local LAN
1325 is boring. Where can I find more interesting captures?
1327 A: We have a collection of strange and exotic sample capture files at
1328 http://wiki.wireshark.org/SampleCaptures
1330 Q 11.3: Why doesn't Wireshark correctly identify RTP packets? It shows
1333 A: Wireshark can identify a UDP datagram as containing a packet of a
1334 particular protocol running atop UDP only if
1335 1. The protocol in question has a particular standard port number, and
1336 the UDP source or destination port number is that port
1337 2. Packets of that protocol can be identified by looking for a
1338 "signature" of some type in the packet - i.e., some data that, if
1339 Wireshark finds it in some particular part of a packet, means that
1340 the packet is almost certainly a packet of that type.
1341 3. Some other traffic earlier in the capture indicated that, for
1342 example, UDP traffic between two particular addresses and ports
1343 will be RTP traffic.
1345 RTP doesn't have a standard port number, so 1) doesn't work; it
1346 doesn't, as far as I know, have any "signature", so 2) doesn't work.
1347 That leaves 3). If there's RTSP traffic that sets up an RTP session,
1348 then, at least in some cases, the RTSP dissector will set things up so
1349 that subsequent RTP traffic will be identified. Currently, that's the
1350 only place we do that; there may be other places.
1351 However, there will always be places where Wireshark is simply
1352 incapable of deducing that a given UDP flow is RTP; a mechanism would
1353 be needed to allow the user to specify that a given conversation should
1354 be treated as RTP. As of Wireshark 0.8.16, such a mechanism exists; if
1355 you select a UDP or TCP packet, the right mouse button menu will have a
1356 "Decode As..." menu item, which will pop up a dialog box letting you
1357 specify that the source port, the destination port, or both the source
1358 and destination ports of the packet should be dissected as some
1359 particular protocol.
1361 Q 11.4: Why doesn't Wireshark show Yahoo Messenger packets in captures
1362 that contain Yahoo Messenger traffic?
1364 A: Wireshark only recognizes as Yahoo Messenger traffic packets to or
1365 from TCP port 3050 that begin with "YPNS", "YHOO", or "YMSG". TCP
1366 segments that start with the middle of a Yahoo Messenger packet that
1367 takes more than one TCP segment will not be recognized as Yahoo
1368 Messenger packets (even if the TCP segment also contains the beginning
1369 of another Yahoo Messenger packet).
1371 12. Filtering traffic
1373 Q 12.1: I saved a filter and tried to use its name to filter the
1374 display; why do I get an "Unexpected end of filter string" error?
1376 A: You cannot use the name of a saved display filter as a filter. To
1377 filter the display, you can enter a display filter expression - not the
1378 name of a saved display filter - in the "Filter:" box at the bottom of
1379 the display, and type the key or press the "Apply" button (that does
1380 not require you to have a saved filter), or, if you want to use a saved
1381 filter, you can press the "Filter:" button, select the filter in the
1382 dialog box that pops up, and press the "OK" button.
1384 Q 12.2: How can I search for, or filter, packets that have a particular
1385 string anywhere in them?
1387 A: If you want to do this when capturing, you can't. That's a feature
1388 that would be hard to implement in capture filters without changes to
1389 the capture filter code, which, on many platforms, is in the OS kernel
1390 and, on other platforms, is in the libpcap library.
1391 In releases prior to 0.9.14, you also can't search for, or filter,
1392 packets containing a particular string even after you've captured them.
1393 In 0.9.14, you can search for, but not filter, packets that have a
1394 particular string; this has been added to the "Find Frame" dialog
1395 ("Find Frame" under the "Edit" menu, or control-F).
1396 In 0.9.15 and later, you can search for those packets using either the
1397 mechanism introduced in 0.9.14 or using the new "contains" operator in
1398 filter expressions, which lets you search the entire packet or text
1399 string or byte string fields in the packet; the "contains" operator can
1400 also be used in expressions used to filter the display.
1402 Q 12.3: How do I filter a capture to see traffic for virus XXX?
1404 A: For some viruses/worms there might be a capture filter to recognize
1405 the virus traffic. Check the CaptureFilters page on the Wireshark Wiki
1406 to see if anybody's added such a filter.
1407 Note that Wireshark was not designed to be an intrusion detection
1408 system; you might be able to use it as an IDS, but in most cases
1409 software designed to be an IDS, such as Snort or Prelude, will probably
1411 The Bleeding Edge of Snort has a collection of signatures for Snort to
1412 detect various viruses, worms, and the like.