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1 office 1 Index
2  
3 1. General Questions:
4  
5 1.1 What is Wireshark?
6  
7 1.2 What's up with the name change? Is Wireshark a fork?
8  
9 1.3 Where can I get help?
10  
11 1.4 What kind of shark is Wireshark?
12  
13 1.5 How is Wireshark pronounced, spelled and capitalized?
14  
15 1.6 How much does Wireshark cost?
16  
17 1.7 But I just paid someone on eBay for a copy of Wireshark!
18 Did I get ripped off?
19  
20 1.8 Can I use Wireshark commercially?
21  
22 1.9 Can I use Wireshark as part of my commercial product?
23  
24 1.10 What protocols are currently supported?
25  
26 1.11 Are there any plans to support {your favorite protocol}?
27  
28 1.12 Can Wireshark read capture files from {your favorite
29 network analyzer}?
30  
31 1.13 What devices can Wireshark use to capture packets?
32  
33 1.14 Does Wireshark work on Windows Vista or Windows Server
34 2008?
35  
36 2. Installing Wireshark:
37  
38 2.1 I installed the Wireshark RPM (or other package); why did
39 it install TShark but not Wireshark?
40  
41 3. Building Wireshark:
42  
43 3.1 I have libpcap installed; why did the configure script not
44 find pcap.h or bpf.h?
45  
46 3.2 Why do I get the error dftest_DEPENDENCIES was already
47 defined in condition TRUE, which implies condition
48 HAVE_PLUGINS_TRUE when I try to build Wireshark from SVN or a
49 SVN snapshot?
50  
51 3.3 Why does the linker fail with a number of "Output line too
52 long." messages followed by linker errors when I try to build
53 Wireshark?
54  
55 3.4 When I try to build Wireshark on Solaris, why does the link
56 fail complaining that plugin_list is undefined?
57  
58 3.5 When I try to build Wireshark on Windows, why does the
59 build fail because of conflicts between winsock.h and
60 winsock2.h?
61  
62 4. Starting Wireshark:
63  
64 4.1 Why does Wireshark crash with a Bus Error when I try to run
65 it on Solaris 8?
66  
67 4.2 When I try to run Wireshark, why does it complain about
68 sprint_realloc_objid being undefined?
69  
70 4.3 I've installed Wireshark from Fink on OS X; why is it very
71 slow to start up?
72  
73 5. Crashes and other fatal errors:
74  
75 5.1 I have an XXX network card on my machine; if I try to
76 capture on it, why does my machine crash or reset itself?
77  
78 5.2 Why does my machine crash or reset itself when I select
79 "Start" from the "Capture" menu or select "Preferences" from
80 the "Edit" menu?
81  
82 6. Capturing packets:
83  
84 6.1 When I use Wireshark to capture packets, why do I see only
85 packets to and from my machine, or not see all the traffic I'm
86 expecting to see from or to the machine I'm trying to monitor?
87  
88 6.2 When I capture with Wireshark, why can't I see any TCP
89 packets other than packets to and from my machine, even though
90 another analyzer on the network sees those packets?
91  
92 6.3 Why am I only seeing ARP packets when I try to capture
93 traffic?
94  
95 6.4 Why am I not seeing any traffic when I try to capture
96 traffic?
97  
98 6.5 Can Wireshark capture on (my T1/E1 line, SS7 links, etc.)?
99  
100 6.6 How do I put an interface into promiscuous mode?
101  
102 6.7 I can set a display filter just fine; why don't capture
103 filters work?
104  
105 6.8 I'm entering valid capture filters; why do I still get
106 "parse error" errors?
107  
108 6.9 How can I capture packets with CRC errors?
109  
110 6.10 How can I capture entire frames, including the FCS?
111  
112 6.11 I'm capturing packets on a machine on a VLAN; why don't
113 the packets I'm capturing have VLAN tags?
114  
115 6.12 Why does Wireshark hang after I stop a capture?
116  
117 7. Capturing packets on Windows:
118  
119 7.1 I'm running Wireshark on Windows; why does some network
120 interface on my machine not show up in the list of interfaces
121 in the "Interface:" field in the dialog box popped up by
122 "Capture->Start", and/or why does Wireshark give me an error if
123 I try to capture on that interface?
124  
125 7.2 I'm running Wireshark on Windows; why do no network
126 interfaces show up in the list of interfaces in the
127 "Interface:" field in the dialog box popped up by
128 "Capture->Start"?
129  
130 7.3 I'm running Wireshark on Windows; why doesn't my serial
131 port/ADSL modem/ISDN modem show up in the list of interfaces in
132 the "Interface:" field in the dialog box popped up by
133 "Capture->Start"?
134  
135 7.4 I'm running Wireshark on Windows NT 4.0/Windows
136 2000/Windows XP/Windows Server 2003; my machine has a PPP
137 (dial-up POTS, ISDN, etc.) interface, and it shows up in the
138 "Interface" item in the "Capture Options" dialog box. Why can
139 no packets be sent on or received from that network while I'm
140 trying to capture traffic on that interface?
141  
142 7.5 I'm running Wireshark on Windows; why am I not seeing any
143 traffic being sent by the machine running Wireshark?
144  
145 7.6 When I capture on Windows in promiscuous mode, I can see
146 packets other than those sent to or from my machine; however,
147 those packets show up with a "Short Frame" indication, unlike
148 packets to or from my machine. What should I do to arrange that
149 I see those packets in their entirety?
150  
151 7.7 I'm trying to capture 802.11 traffic on Windows; why am I
152 not seeing any packets?
153  
154 7.8 I'm trying to capture 802.11 traffic on Windows; why am I
155 seeing packets received by the machine on which I'm capturing
156 traffic, but not packets sent by that machine?
157  
158 7.9 I'm trying to capture Ethernet VLAN traffic on Windows, and
159 I'm capturing on a "raw" Ethernet device rather than a "VLAN
160 interface", so that I can see the VLAN headers; why am I seeing
161 packets received by the machine on which I'm capturing traffic,
162 but not packets sent by that machine?
163  
164 8. Capturing packets on UN*Xes:
165  
166 8.1 I'm running Wireshark on a UNIX-flavored OS; why does some
167 network interface on my machine not show up in the list of
168 interfaces in the "Interface:" field in the dialog box popped
169 up by "Capture->Start", and/or why does Wireshark give me an
170 error if I try to capture on that interface?
171  
172 8.2 I'm running Wireshark on a UNIX-flavored OS; why do no
173 network interfaces show up in the list of interfaces in the
174 "Interface:" field in the dialog box popped up by
175 "Capture->Start"?
176  
177 8.3 I'm capturing packets on Linux; why do the time stamps have
178 only 100ms resolution, rather than 1us resolution?
179  
180 9. Capturing packets on wireless LANs:
181  
182 9.1 How can I capture raw 802.11 frames, including non-data
183 (management, beacon) frames?
184  
185 9.2 How do I capture on an 802.11 device in monitor mode?
186  
187 10. Viewing traffic:
188  
189 10.1 Why am I seeing lots of packets with incorrect TCP
190 checksums?
191  
192 10.2 I've just installed Wireshark, and the traffic on my local
193 LAN is boring. Where can I find more interesting captures?
194  
195 10.3 Why doesn't Wireshark correctly identify RTP packets? It
196 shows them only as UDP.
197  
198 10.4 Why doesn't Wireshark show Yahoo Messenger packets in
199 captures that contain Yahoo Messenger traffic?
200  
201 11. Filtering traffic:
202  
203 11.1 I saved a filter and tried to use its name to filter the
204 display; why do I get an "Unexpected end of filter string"
205 error?
206  
207 11.2 How can I search for, or filter, packets that have a
208 particular string anywhere in them?
209  
210 11.3 How do I filter a capture to see traffic for virus XXX?
211  
212 1. General Questions
213  
214 Q 1.1: What is Wireshark?
215  
216 A: Wireshark® is a network protocol analyzer. It lets you
217 capture and interactively browse the traffic running on a
218 computer network. It has a rich and powerful feature set and is
219 world's most popular tool of its kind. It runs on most
220 computing platforms including Windows, OS X, Linux, and UNIX.
221 Network professionals, security experts, developers, and
222 educators around the world use it regularly. It is freely
223 available as open source, and is released under the GNU General
224 Public License version 2.
225 It is developed and maintained by a global team of protocol
226 experts, and it is an example of a disruptive technology.
227 Wireshark used to be known as Ethereal®. See the next question
228 for details about the name change. If you're still using
229 Ethereal, it is strongly recommended that you upgrade to
230 Wireshark as Ethereal is unsupported and has known security
231 vulnerabilities.
232 For more information, please see the About Wireshark page.
233  
234 Q 1.2: What's up with the name change? Is Wireshark a fork?
235  
236 A: In May of 2006, Gerald Combs (the original author of
237 Ethereal) went to work for CACE Technologies (best known for
238 WinPcap). Unfortunately, he had to leave the Ethereal
239 trademarks behind.
240 This left the project in an awkward position. The only
241 reasonable way to ensure the continued success of the project
242 was to change the name. This is how Wireshark was born.
243 Wireshark is almost (but not quite) a fork. Normally a "fork"
244 of an open source project results in two names, web sites,
245 development teams, support infrastructures, etc. This is the
246 case with Wireshark except for one notable exception -- every
247 member of the core development team is now working on
248 Wireshark. There has been no active development on Ethereal
249 since the name change. Several parts of the Ethereal web site
250 (such as the mailing lists, source code repository, and build
251 farm) have gone offline.
252 More information on the name change can be found here:
253  
254 * Original press release
255 * NewsForge article
256 * Many other articles in our bibliography
257  
258 Q 1.3: Where can I get help?
259  
260 A: Community support is available on the Q&A site and on the
261 wireshark-users mailing list. Subscription information and
262 archives for all of Wireshark's mailing lists can be found at
263 https://www.wireshark.org/mailman/listinfo. An IRC channel
264 dedicated to Wireshark can be found at
265 irc://irc.freenode.net/wireshark.
266 Self-paced and instructor-led training is available at
267 Wireshark University. Wireshark University also offers
268 certification via the Wireshark Certified Network Analyst
269 program.
270  
271 Q 1.4: What kind of shark is Wireshark?
272  
273 A: carcharodon photoshopia.
274  
275 Q 1.5: How is Wireshark pronounced, spelled and capitalized?
276  
277 A: Wireshark is pronounced as the word wire followed
278 immediately by the word shark. Exact pronunciation and emphasis
279 may vary depending on your locale (e.g. Arkansas).
280 It's spelled with a capital W, followed by a lower-case
281 ireshark. It is not a CamelCase word, i.e., WireShark is
282 incorrect.
283  
284 Q 1.6: How much does Wireshark cost?
285  
286 A: Wireshark is "free software"; you can download it without
287 paying any license fee. The version of Wireshark you download
288 isn't a "demo" version, with limitations not present in a
289 "full" version; it is the full version.
290 The license under which Wireshark is issued is the GNU General
291 Public License version 2. See the GNU GPL FAQ for some more
292 information.
293  
294 Q 1.7: But I just paid someone on eBay for a copy of Wireshark!
295 Did I get ripped off?
296  
297 A: That depends. Did they provide any sort of value-added
298 product or service, such as installation support, installation
299 media, training, trace file analysis, or funky-colored
300 shark-themed socks? Probably not.
301 Wireshark is available for anyone to download, absolutely free,
302 at any time. Paying for a copy implies that you should get
303 something for your money.
304  
305 Q 1.8: Can I use Wireshark commercially?
306  
307 A: Yes, if, for example, you mean "I work for a commercial
308 organization; can I use Wireshark to capture and analyze
309 network traffic in our company's networks or in our customer's
310 networks?"
311 If you mean "Can I use Wireshark as part of my commercial
312 product?", see the next entry in the FAQ.
313  
314 Q 1.9: Can I use Wireshark as part of my commercial product?
315  
316 A: As noted, Wireshark is licensed under the GNU General Public
317 License, version 2. The GPL imposes conditions on your use of
318 GPL'ed code in your own products; you cannot, for example, make
319 a "derived work" from Wireshark, by making modifications to it,
320 and then sell the resulting derived work and not allow
321 recipients to give away the resulting work. You must also make
322 the changes you've made to the Wireshark source available to
323 all recipients of your modified version; those changes must
324 also be licensed under the terms of the GPL. See the GPL FAQ
325 for more details; in particular, note the answer to the
326 question about modifying a GPLed program and selling it
327 commercially, and the question about linking GPLed code with
328 other code to make a proprietary program.
329 You can combine a GPLed program such as Wireshark and a
330 commercial program as long as they communicate "at arm's
331 length", as per this item in the GPL FAQ.
332 We recommend keeping Wireshark and your product completely
333 separate, communicating over sockets or pipes. If you're
334 loading any part of Wireshark as a DLL, you're probably doing
335 it wrong.
336  
337 Q 1.10: What protocols are currently supported?
338  
339 A: There are currently hundreds of supported protocols and
340 media. Details can be found in the wireshark(1) man page.
341  
342 Q 1.11: Are there any plans to support {your favorite
343 protocol}?
344  
345 A: Support for particular protocols is added to Wireshark as a
346 result of people contributing that support; no formal plans for
347 adding support for particular protocols in particular future
348 releases exist.
349  
350 Q 1.12: Can Wireshark read capture files from {your favorite
351 network analyzer}?
352  
353 A: Support for particular capture file formats is added to
354 Wireshark as a result of people contributing that support; no
355 formal plans for adding support for particular capture file
356 formats in particular future releases exist.
357 If a network analyzer writes out files in a format already
358 supported by Wireshark (e.g., in libpcap format), Wireshark may
359 already be able to read them, unless the analyzer has added its
360 own proprietary extensions to that format.
361 If a network analyzer writes out files in its own format, or
362 has added proprietary extensions to another format, in order to
363 make Wireshark read captures from that network analyzer, we
364 would either have to have a specification for the file format,
365 or the extensions, sufficient to give us enough information to
366 read the parts of the file relevant to Wireshark, or would need
367 at least one capture file in that format AND a detailed textual
368 analysis of the packets in that capture file (showing packet
369 time stamps, packet lengths, and the top-level packet header)
370 in order to reverse-engineer the file format.
371 Note that there is no guarantee that we will be able to
372 reverse-engineer a capture file format.
373  
374 Q 1.13: What devices can Wireshark use to capture packets?
375  
376 A: Wireshark can read live data from Ethernet, Token-Ring,
377 FDDI, serial (PPP and SLIP) (if the OS on which it's running
378 allows Wireshark to do so), 802.11 wireless LAN (if the OS on
379 which it's running allows Wireshark to do so), ATM connections
380 (if the OS on which it's running allows Wireshark to do so),
381 and the "any" device supported on Linux by recent versions of
382 libpcap.
383 See the list of supported capture media on various OSes for
384 details (several items in there say "Unknown", which doesn't
385 mean "Wireshark can't capture on them", it means "we don't know
386 whether it can capture on them"; we expect that it will be able
387 to capture on many of them, but we haven't tried it ourselves -
388 if you try one of those types and it works, please update the
389 wiki page accordingly.
390 It can also read a variety of capture file formats, including:
391  
392 * AG Group/WildPackets/Savvius
393 EtherPeek/TokenPeek/AiroPeek/EtherHelp/Packet Grabber
394 captures
395 * AIX's iptrace captures
396 * Accellent's 5Views LAN agent output
397 * Cinco Networks NetXRay captures
398 * Cisco Secure Intrusion Detection System IPLog output
399 * CoSine L2 debug output
400 * DBS Etherwatch VMS text output
401 * Endace Measurement Systems' ERF format captures
402 * EyeSDN USB S0 traces
403 * HP-UX nettl captures
404 * ISDN4BSD project i4btrace captures
405 * Linux Bluez Bluetooth stack hcidump -w traces
406 * Lucent/Ascend router debug output
407 * Microsoft Network Monitor captures
408 * Network Associates Windows-based Sniffer captures
409 * Network General/Network Associates DOS-based Sniffer
410 (compressed or uncompressed) captures
411 * Network Instruments Observer version 9 captures
412 * Novell LANalyzer captures
413 * RADCOM's WAN/LAN analyzer captures
414 * Shomiti/Finisar Surveyor captures
415 * Toshiba's ISDN routers dump output
416 * VMS TCPIPtrace/TCPtrace/UCX$TRACE output
417 * Visual Networks' Visual UpTime traffic capture
418 * libpcap, tcpdump and various other tools using tcpdump's
419 capture format
420 * snoop and atmsnoop output
421  
422 so that it can read traces from various network types, as
423 captured by other applications or equipment, even if it cannot
424 itself capture on those network types.
425  
426 Q 1.14: Does Wireshark work on Windows Vista or Windows Server
427 2008?
428  
429 A: Yes, but if you want to capture packets as a normal user,
430 you must make sure npf.sys is loaded. Wireshark's installer
431 enables this by default. This is not a concern if you run
432 Wireshark as Administrator, but this is discouraged. See the
433 CapturePrivileges page on the wiki for more details.
434  
435 2. Installing Wireshark
436  
437 Q 2.1: I installed the Wireshark RPM (or other package); why
438 did it install TShark but not Wireshark?
439  
440 A: Many distributions have separate Wireshark packages, one for
441 non-GUI components such as TShark, editcap, dumpcap, etc. and
442 one for the GUI. If this is the case on your system, there's
443 probably a separate package named wireshark-gnome or
444 wireshark-gtk+. Find it and install it.
445  
446 3. Building Wireshark
447  
448 Q 3.1: I have libpcap installed; why did the configure script
449 not find pcap.h or bpf.h?
450  
451 A: Are you sure pcap.h and bpf.h are installed? The official
452 distribution of libpcap only installs the libpcap.a library
453 file when "make install" is run. To install pcap.h and bpf.h,
454 you must run "make install-incl". If you're running Debian or
455 Redhat, make sure you have the "libpcap-dev" or "libpcap-devel"
456 packages installed.
457 It's also possible that pcap.h and bpf.h have been installed in
458 a strange location. If this is the case, you may have to tweak
459 aclocal.m4.
460  
461 Q 3.2: Why do I get the error dftest_DEPENDENCIES was already
462 defined in condition TRUE, which implies condition
463 HAVE_PLUGINS_TRUE when I try to build Wireshark from SVN or a
464 SVN snapshot?
465  
466 A: You probably have automake 1.5 installed on your machine
467 (the command automake --version will report the version of
468 automake on your machine). There is a bug in that version of
469 automake that causes this problem; upgrade to a later version
470 of automake (1.6 or later).
471  
472 Q 3.3: Why does the linker fail with a number of "Output line
473 too long." messages followed by linker errors when I try to
474 build Wireshark?
475  
476 A: The version of the sed command on your system is incapable
477 of handling very long lines. On Solaris, for example,
478 /usr/bin/sed has a line length limit too low to allow libtool
479 to work; /usr/xpg4/bin/sed can handle it, as can GNU sed if you
480 have it installed.
481 On Solaris, changing your command search path to search
482 /usr/xpg4/bin before /usr/bin should make the problem go away;
483 on any platform on which you have this problem, installing GNU
484 sed and changing your command path to search the directory in
485 which it is installed before searching the directory with the
486 version of sed that came with the OS should make the problem go
487 away.
488  
489 Q 3.4: When I try to build Wireshark on Solaris, why does the
490 link fail complaining that plugin_list is undefined?
491  
492 A: This appears to be due to a problem with some versions of
493 the GTK+ and GLib packages from www.sunfreeware.org; un-install
494 those packages, and try getting the 1.2.10 versions from that
495 site, or the versions from The Written Word, or the versions
496 from Sun's GNOME distribution, or the versions from the
497 supplemental software CD that comes with the Solaris media kit,
498 or build them from source from the GTK Web site. Then re-run
499 the configuration script, and try rebuilding Wireshark. (If you
500 get the 1.2.10 versions from www.sunfreeware.org, and the
501 problem persists, un-install them and try installing one of the
502 other versions mentioned.)
503  
504 Q 3.5: When I try to build Wireshark on Windows, why does the
505 build fail because of conflicts between winsock.h and
506 winsock2.h?
507  
508 A: As of Wireshark 0.9.5, you must install WinPcap 2.3 or
509 later, and the corresponding version of the developer's pack,
510 in order to be able to compile Wireshark; it will not compile
511 with older versions of the developer's pack. The symptoms of
512 this failure are conflicts between definitions in winsock.h and
513 in winsock2.h; Wireshark uses winsock2.h, but pre-2.3 versions
514 of the WinPcap developer's packet use winsock.h. (2.3 uses
515 winsock2.h, so if Wireshark were to use winsock.h, it would not
516 be able to build with current versions of the WinPcap
517 developer's pack.)
518 Note that the installed version of the developer's pack should
519 be the same version as the version of WinPcap you have
520 installed.
521  
522 4. Starting Wireshark
523  
524 Q 4.1: Why does Wireshark crash with a Bus Error when I try to
525 run it on Solaris 8?
526  
527 A: Some versions of the GTK+ library from www.sunfreeware.org
528 appear to be buggy, causing Wireshark to drop core with a Bus
529 Error. Un-install those packages, and try getting the 1.2.10
530 version from that site, or the version from The Written Word,
531 or the version from Sun's GNOME distribution, or the version
532 from the supplemental software CD that comes with the Solaris
533 media kit, or build it from source from the GTK Web site.
534 Update the GLib library to the 1.2.10 version, from the same
535 source, as well. (If you get the 1.2.10 versions from
536 www.sunfreeware.org, and the problem persists, un-install them
537 and try installing one of the other versions mentioned.)
538 Similar problems may exist with older versions of GTK+ for
539 earlier versions of Solaris.
540  
541 Q 4.2: When I try to run Wireshark, why does it complain about
542 sprint_realloc_objid being undefined?
543  
544 A: Wireshark can only be linked with version 4.2.2 or later of
545 UCD SNMP. Your version of Wireshark was dynamically linked with
546 such a version of UCD SNMP; however, you have an older version
547 of UCD SNMP installed, which means that when Wireshark is run,
548 it tries to link to the older version, and fails. You will have
549 to replace that version of UCD SNMP with version 4.2.2 or a
550 later version.
551  
552 Q 4.3: I've installed Wireshark from Fink on OS X; why is it
553 very slow to start up?
554  
555 A: When an application is installed on OS X, prior to 10.4, it
556 is usually "prebound" to speed up launching the application.
557 (That's what the "Optimizing" phase of installation is.)
558 Fink normally performs prebinding automatically when you
559 install a package. However, in some rare cases, for whatever
560 reason the prebinding caches get corrupt, and then not only
561 does prebinding fail, but startup actually becomes much slower,
562 because the system tries in vain to perform prebinding "on the
563 fly" as you launch the application. This fails, causing
564 sometimes huge delays.
565 To fix the prebinding caches, run the command
566  
567  
568 sudo /sw/var/lib/fink/prebound/update-package-prebinding.pl -f
569  
570  
571 5. Crashes and other fatal errors
572  
573 Q 5.1: I have an XXX network card on my machine; if I try to
574 capture on it, why does my machine crash or reset itself?
575  
576 A: This is almost certainly a problem with one or more of:
577  
578 * the operating system you're using;
579 * the device driver for the interface you're using;
580 * the libpcap/WinPcap library and, if this is Windows, the
581 WinPcap device driver;
582  
583 so:
584  
585 * if you are using Windows, see the WinPcap support page -
586 check the "Submitting bugs" section;
587 * if you are using some Linux distribution, some version of
588 BSD, or some other UNIX-flavored OS, you should report the
589 problem to the company or organization that produces the OS
590 (in the case of a Linux distribution, report the problem to
591 whoever produces the distribution).
592  
593 Q 5.2: Why does my machine crash or reset itself when I select
594 "Start" from the "Capture" menu or select "Preferences" from
595 the "Edit" menu?
596  
597 A: Both of those operations cause Wireshark to try to build a
598 list of the interfaces that it can open; it does so by getting
599 a list of interfaces and trying to open them. There is probably
600 an OS, driver, or, for Windows, WinPcap bug that causes the
601 system to crash when this happens; see the previous question.
602  
603 6. Capturing packets
604  
605 Q 6.1: When I use Wireshark to capture packets, why do I see
606 only packets to and from my machine, or not see all the traffic
607 I'm expecting to see from or to the machine I'm trying to
608 monitor?
609  
610 A: This might be because the interface on which you're
611 capturing is plugged into an Ethernet or Token Ring switch; on
612 a switched network, unicast traffic between two ports will not
613 necessarily appear on other ports - only broadcast and
614 multicast traffic will be sent to all ports.
615 Note that even if your machine is plugged into a hub, the "hub"
616 may be a switched hub, in which case you're still on a switched
617 network.
618 Note also that on the Linksys Web site, they say that their
619 auto-sensing hubs "broadcast the 10Mb packets to the port that
620 operate at 10Mb only and broadcast the 100Mb packets to the
621 ports that operate at 100Mb only", which would indicate that if
622 you sniff on a 10Mb port, you will not see traffic coming sent
623 to a 100Mb port, and vice versa. This problem has also been
624 reported for Netgear dual-speed hubs, and may exist for other
625 "auto-sensing" or "dual-speed" hubs.
626 Some switches have the ability to replicate all traffic on all
627 ports to a single port so that you can plug your analyzer into
628 that single port to sniff all traffic. You would have to check
629 the documentation for the switch to see if this is possible
630 and, if so, to see how to do this. See the switch reference
631 page on the Wireshark Wiki for information on some switches.
632 (Note that it's a Wiki, so you can update or fix that
633 information, or add additional information on those switches or
634 information on new switches, yourself.)
635 Note also that many firewall/NAT boxes have a switch built into
636 them; this includes many of the "cable/DSL router" boxes. If
637 you have a box of that sort, that has a switch with some number
638 of Ethernet ports into which you plug machines on your network,
639 and another Ethernet port used to connect to a cable or DSL
640 modem, you can, at least, sniff traffic between the machines on
641 your network and the Internet by plugging the Ethernet port on
642 the router going to the modem, the Ethernet port on the modem,
643 and the machine on which you're running Wireshark into a hub
644 (make sure it's not a switching hub, and that, if it's a
645 dual-speed hub, all three of those ports are running at the
646 same speed.
647 If your machine is not plugged into a switched network or a
648 dual-speed hub, or it is plugged into a switched network but
649 the port is set up to have all traffic replicated to it, the
650 problem might be that the network interface on which you're
651 capturing doesn't support "promiscuous" mode, or because your
652 OS can't put the interface into promiscuous mode. Normally,
653 network interfaces supply to the host only:
654  
655 * packets sent to one of that host's link-layer addresses;
656 * broadcast packets;
657 * multicast packets sent to a multicast address that the host
658 has configured the interface to accept.
659  
660 Most network interfaces can also be put in "promiscuous" mode,
661 in which they supply to the host all network packets they see.
662 Wireshark will try to put the interface on which it's capturing
663 into promiscuous mode unless the "Capture packets in
664 promiscuous mode" option is turned off in the "Capture Options"
665 dialog box, and TShark will try to put the interface on which
666 it's capturing into promiscuous mode unless the -p option was
667 specified. However, some network interfaces don't support
668 promiscuous mode, and some OSes might not allow interfaces to
669 be put into promiscuous mode.
670 If the interface is not running in promiscuous mode, it won't
671 see any traffic that isn't intended to be seen by your machine.
672 It will see broadcast packets, and multicast packets sent to a
673 multicast MAC address the interface is set up to receive.
674 You should ask the vendor of your network interface whether it
675 supports promiscuous mode. If it does, you should ask whoever
676 supplied the driver for the interface (the vendor, or the
677 supplier of the OS you're running on your machine) whether it
678 supports promiscuous mode with that network interface.
679 In the case of token ring interfaces, the drivers for some of
680 them, on Windows, may require you to enable promiscuous mode in
681 order to capture in promiscuous mode. See the Wireshark Wiki
682 item on Token Ring capturing for details.
683 In the case of wireless LAN interfaces, it appears that, when
684 those interfaces are promiscuously sniffing, they're running in
685 a significantly different mode from the mode that they run in
686 when they're just acting as network interfaces (to the extent
687 that it would be a significant effort for those drivers to
688 support for promiscuously sniffing and acting as regular
689 network interfaces at the same time), so it may be that Windows
690 drivers for those interfaces don't support promiscuous mode.
691  
692 Q 6.2: When I capture with Wireshark, why can't I see any TCP
693 packets other than packets to and from my machine, even though
694 another analyzer on the network sees those packets?
695  
696 A: You're probably not seeing any packets other than unicast
697 packets to or from your machine, and broadcast and multicast
698 packets; a switch will normally send to a port only unicast
699 traffic sent to the MAC address for the interface on that port,
700 and broadcast and multicast traffic - it won't send to that
701 port unicast traffic sent to a MAC address for some other
702 interface - and a network interface not in promiscuous mode
703 will receive only unicast traffic sent to the MAC address for
704 that interface, broadcast traffic, and multicast traffic sent
705 to a multicast MAC address the interface is set up to receive.
706 TCP doesn't use broadcast or multicast, so you will only see
707 your own TCP traffic, but UDP services may use broadcast or
708 multicast so you'll see some UDP traffic - however, this is not
709 a problem with TCP traffic, it's a problem with unicast
710 traffic, as you also won't see all UDP traffic between other
711 machines.
712 I.e., this is probably the same question as this earlier one;
713 see the response to that question.
714  
715 Q 6.3: Why am I only seeing ARP packets when I try to capture
716 traffic?
717  
718 A: You're probably on a switched network, and running Wireshark
719 on a machine that's not sending traffic to the switch and not
720 being sent any traffic from other machines on the switch. ARP
721 packets are often broadcast packets, which are sent to all
722 switch ports.
723 I.e., this is probably the same question as this earlier one;
724 see the response to that question.
725  
726 Q 6.4: Why am I not seeing any traffic when I try to capture
727 traffic?
728  
729 A: Is the machine running Wireshark sending out any traffic on
730 the network interface on which you're capturing, or receiving
731 any traffic on that network, or is there any broadcast traffic
732 on the network or multicast traffic to a multicast group to
733 which the machine running Wireshark belongs?
734 If not, this may just be a problem with promiscuous sniffing,
735 either due to running on a switched network or a dual-speed
736 hub, or due to problems with the interface not supporting
737 promiscuous mode; see the response to this earlier question.
738 Otherwise, on Windows, see the response to this question and,
739 on a UNIX-flavored OS, see the response to this question.
740  
741 Q 6.5: Can Wireshark capture on (my T1/E1 line, SS7 links,
742 etc.)?
743  
744 A: Wireshark can only capture on devices supported by
745 libpcap/WinPcap. On most OSes, only devices that can act as
746 network interfaces of the type that support IP are supported as
747 capture devices for libpcap/WinPcap, although the device
748 doesn't necessarily have to be running as an IP interface in
749 order to support traffic capture.
750 On Linux and FreeBSD, libpcap 0.8 and later support the API for
751 Endace Measurement Systems' DAG cards, so that a system with
752 one of those cards, and its driver and libraries, installed can
753 capture traffic with those cards with libpcap-based
754 applications. You would either have to have a version of
755 Wireshark built with that version of libpcap, or a
756 dynamically-linked version of Wireshark and a shared libpcap
757 library with DAG support, in order to do so with Wireshark. You
758 should ask Endace whether that could be used to capture traffic
759 on, for example, your T1/E1 link.
760 See the SS7 capture setup page on the Wireshark Wiki for
761 current information on capturing SS7 traffic on TDM links.
762  
763 Q 6.6: How do I put an interface into promiscuous mode?
764  
765 A: By not disabling promiscuous mode when running Wireshark or
766 TShark.
767 Note, however, that:
768  
769 * the form of promiscuous mode that libpcap (the library that
770 programs such as tcpdump, Wireshark, etc. use to do packet
771 capture) turns on will not necessarily be shown if you run
772 ifconfig on the interface on a UNIX system;
773 * some network interfaces might not support promiscuous mode,
774 and some drivers might not allow promiscuous mode to be
775 turned on - see this earlier question for more information
776 on that;
777 * the fact that you're not seeing any traffic, or are only
778 seeing broadcast traffic, or aren't seeing any
779 non-broadcast traffic other than traffic to or from the
780 machine running Wireshark, does not mean that promiscuous
781 mode isn't on - see this earlier question for more
782 information on that.
783  
784 I.e., this is probably the same question as this earlier one;
785 see the response to that question.
786  
787 Q 6.7: I can set a display filter just fine; why don't capture
788 filters work?
789  
790 A: Capture filters currently use a different syntax than
791 display filters. Here's the corresponding section from the
792 wireshark(1) man page:
793 "Display filters in Wireshark are very powerful; more fields
794 are filterable in Wireshark than in other protocol analyzers,
795 and the syntax you can use to create your filters is richer. As
796 Wireshark progresses, expect more and more protocol fields to
797 be allowed in display filters.
798 Packet capturing is performed with the pcap library. The
799 capture filter syntax follows the rules of the pcap library.
800 This syntax is different from the display filter syntax."
801 The capture filter syntax used by libpcap can be found in the
802 tcpdump(8) man page.
803  
804 Q 6.8: I'm entering valid capture filters; why do I still get
805 "parse error" errors?
806  
807 A: There is a bug in some versions of libpcap/WinPcap that
808 cause it to report parse errors even for valid expressions if a
809 previous filter expression was invalid and got a parse error.
810 Try exiting and restarting Wireshark; if you are using a
811 version of libpcap/WinPcap with this bug, this will "erase" its
812 memory of the previous parse error. If the capture filter that
813 got the "parse error" now works, the earlier error with that
814 filter was probably due to this bug.
815 The bug was fixed in libpcap 0.6; 0.4[.x] and 0.5[.x] versions
816 of libpcap have this bug, but 0.6[.x] and later versions don't.
817 Versions of WinPcap prior to 2.3 are based on pre-0.6 versions
818 of libpcap, and have this bug; WinPcap 2.3 is based on libpcap
819 0.6.2, and doesn't have this bug.
820 If you are running Wireshark on a UNIX-flavored platform, run
821 "wireshark -v", or select "About Wireshark..." from the "Help"
822 menu in Wireshark, to see what version of libpcap it's using.
823 If it's not 0.6 or later, you will need either to upgrade your
824 OS to get a later version of libpcap, or will need to build and
825 install a later version of libpcap from the tcpdump.org Web
826 site and then recompile Wireshark from source with that later
827 version of libpcap.
828 If you are running Wireshark on Windows with a pre-2.3 version
829 of WinPcap, you will need to un-install WinPcap and then
830 download and install WinPcap 2.3.
831  
832 Q 6.9: How can I capture packets with CRC errors?
833  
834 A: Wireshark can capture only the packets that the packet
835 capture library - libpcap on UNIX-flavored OSes, and the
836 WinPcap port to Windows of libpcap on Windows - can capture,
837 and libpcap/WinPcap can capture only the packets that the OS's
838 raw packet capture mechanism (or the WinPcap driver, and the
839 underlying OS networking code and network interface drivers, on
840 Windows) will allow it to capture.
841 Unless the OS always supplies packets with errors such as
842 invalid CRCs to the raw packet capture mechanism, or can be
843 configured to do so, invalid CRCs to the raw packet capture
844 mechanism, Wireshark - and other programs that capture raw
845 packets, such as tcpdump - cannot capture those packets. You
846 will have to determine whether your OS needs to be so
847 configured and, if so, can be so configured, configure it if
848 necessary and possible, and make whatever changes to libpcap
849 and the packet capture program you're using are necessary, if
850 any, to support capturing those packets.
851 Most OSes probably do not support capturing packets with
852 invalid CRCs on Ethernet, and probably do not support it on
853 most other link-layer types. Some drivers on some OSes do
854 support it, such as some Ethernet drivers on FreeBSD; in those
855 OSes, you might always get those packets, or you might only get
856 them if you capture in promiscuous mode (you'd have to
857 determine which is the case).
858 Note that libpcap does not currently supply to programs that
859 use it an indication of whether the packet's CRC was invalid
860 (because the drivers themselves do not supply that information
861 to the raw packet capture mechanism); therefore, Wireshark will
862 not indicate which packets had CRC errors unless the FCS was
863 captured (see the next question) and you're using Wireshark
864 0.9.15 and later, in which case Wireshark will check the CRC
865 and indicate whether it's correct or not.
866  
867 Q 6.10: How can I capture entire frames, including the FCS?
868  
869 A: Wireshark can only capture data that the packet capture
870 library - libpcap on UNIX-flavored OSes, and the WinPcap port
871 to Windows of libpcap on Windows - can capture, and
872 libpcap/WinPcap can capture only the data that the OS's raw
873 packet capture mechanism (or the WinPcap driver, and the
874 underlying OS networking code and network interface drivers, on
875 Windows) will allow it to capture.
876 For any particular link-layer network type, unless the OS
877 supplies the FCS of a frame as part of the frame, or can be
878 configured to do so, Wireshark - and other programs that
879 capture raw packets, such as tcpdump - cannot capture the FCS
880 of a frame. You will have to determine whether your OS needs to
881 be so configured and, if so, can be so configured, configure it
882 if necessary and possible, and make whatever changes to libpcap
883 and the packet capture program you're using are necessary, if
884 any, to support capturing the FCS of a frame.
885 Most OSes do not support capturing the FCS of a frame on
886 Ethernet, and probably do not support it on most other
887 link-layer types. Some drivres on some OSes do support it, such
888 as some (all?) Ethernet drivers on NetBSD and possibly the
889 driver for Apple's gigabit Ethernet interface in OS X; in those
890 OSes, you might always get the FCS, or you might only get the
891 FCS if you capture in promiscuous mode (you'd have to determine
892 which is the case).
893 Versions of Wireshark prior to 0.9.15 will not treat an
894 Ethernet FCS in a captured packet as an FCS. 0.9.15 and later
895 will attempt to determine whether there's an FCS at the end of
896 the frame and, if it thinks there is, will display it as such,
897 and will check whether it's the correct CRC-32 value or not.
898  
899 Q 6.11: I'm capturing packets on a machine on a VLAN; why don't
900 the packets I'm capturing have VLAN tags?
901  
902 A: You might be capturing on what might be called a "VLAN
903 interface" - the way a particular OS makes VLANs plug into the
904 networking stack might, for example, be to have a network
905 device object for the physical interface, which takes VLAN
906 packets, strips off the VLAN header and constructs an Ethernet
907 header, and passes that packet to an internal network device
908 object for the VLAN, which then passes the packets onto various
909 higher-level protocol implementations.
910 In order to see the raw Ethernet packets, rather than
911 "de-VLANized" packets, you would have to capture not on the
912 virtual interface for the VLAN, but on the interface
913 corresponding to the physical network device, if possible. See
914 the Wireshark Wiki item on VLAN capturing for details.
915  
916 Q 6.12: Why does Wireshark hang after I stop a capture?
917  
918 A: The most likely reason for this is that Wireshark is trying
919 to look up an IP address in the capture to convert it to a name
920 (so that, for example, it can display the name in the source
921 address or destination address columns), and that lookup
922 process is taking a very long time.
923 Wireshark calls a routine in the OS of the machine on which
924 it's running to convert of IP addresses to the corresponding
925 names. That routine probably does one or more of:
926  
927 * a search of a system file listing IP addresses and names;
928 * a lookup using DNS;
929 * on UNIX systems, a lookup using NIS;
930 * on Windows systems, a NetBIOS-over-TCP query.
931  
932 If a DNS server that's used in an address lookup is not
933 responding, the lookup will fail, but will only fail after a
934 timeout while the system routine waits for a reply.
935 In addition, on Windows systems, if the DNS lookup of the
936 address fails, either because the server isn't responding or
937 because there are no records in the DNS that could be used to
938 map the address to a name, a NetBIOS-over-TCP query will be
939 made. That query involves sending a message to the
940 NetBIOS-over-TCP name service on that machine, asking for the
941 name and other information about the machine. If the machine
942 isn't running software that responds to those queries - for
943 example, many non-Windows machines wouldn't be running that
944 software - the lookup will only fail after a timeout. Those
945 timeouts can cause the lookup to take a long time.
946 If you disable network address-to-name translation - for
947 example, by turning off the "Enable network name resolution"
948 option in the "Capture Options" dialog box for starting a
949 network capture - the lookups of the address won't be done,
950 which may speed up the process of reading the capture file
951 after the capture is stopped. You can make that setting the
952 default by selecting "Preferences" from the "Edit" menu,
953 turning off the "Enable network name resolution" option in the
954 "Name resolution" options in the preferences disalog box, and
955 using the "Save" button in that dialog box; note that this will
956 save all your current preference settings.
957 If Wireshark hangs when reading a capture even with network
958 name resolution turned off, there might, for example, be a bug
959 in one of Wireshark's dissectors for a protocol causing it to
960 loop infinitely. If you're not running the most recent release
961 of Wireshark, you should first upgrade to that release, as, if
962 there's a bug of that sort, it might've been fixed in a release
963 after the one you're running. If the hang occurs in the most
964 recent release of Wireshark, the bug should be reported to the
965 Wireshark developers' mailing list at
966 wireshark-dev@wireshark.org.
967 On UNIX-flavored OSes, please try to force Wireshark to dump
968 core, by sending it a SIGABRT signal (usually signal 6) with
969 the kill command, and then get a stack trace if you have a
970 debugger installed. A stack trace can be obtained by using your
971 debugger (gdb in this example), the Wireshark binary, and the
972 resulting core file. Here's an example of how to use the gdb
973 command backtrace to do so.
974  
975  
976 $ gdb wireshark core
977 (gdb) backtrace
978 ..... prints the stack trace
979 (gdb) quit
980 $
981  
982  
983 The core dump file may be named "wireshark.core" rather than
984 "core" on some platforms (e.g., BSD systems).
985 Also, if at all possible, please send a copy of the capture
986 file that caused the problem. When capturing packets, Wireshark
987 normally writes captured packets to a temporary file, which
988 will probably be in /tmp or /var/tmp on UNIX-flavored OSes,
989 \TEMP on the main system disk (normally \Documents and
990 Settings\your login name \Local Settings\Temp on the main
991 system disk on Windows Windows XP and Server 2003, and
992 \Users\your login name\AppData\Local\Temp on the main system
993 disk on Windows Vista and later, so the capture file will
994 probably be there. If you are capturing on a single interface,
995 it will have a name of the form,
996 wireshark_<iface>_YYYYmmddHHMMSS_XXXXXX.<fmt>, where <fmt> is
997 the capture file format (pcap or pcapng), and <iface> is the
998 actual name of the interface you are capturing on; otherwise,
999 if you are capturing on multiple interfaces, it will have a
1000 name of the form,
1001 wireshark_<N>_interfaces_YYYYmmddHHMMSS_XXXXXX.<fmt>, where <N>
1002 is the number of simultaneous interfaces you are capturing on.
1003 Please don't send a trace file greater than 1 MB when
1004 compressed; instead, make it available via FTP or HTTP, or say
1005 it's available but leave it up to a developer to ask for it. If
1006 the trace file contains sensitive information (e.g.,
1007 passwords), then please do not send it.
1008  
1009 7. Capturing packets on Windows
1010  
1011 Q 7.1: I'm running Wireshark on Windows; why does some network
1012 interface on my machine not show up in the list of interfaces
1013 in the "Interface:" field in the dialog box popped up by
1014 "Capture->Start", and/or why does Wireshark give me an error if
1015 I try to capture on that interface?
1016  
1017 A: If you are running Wireshark on Windows XP, or Windows
1018 Server 2003, and this is the first time you have run a
1019 WinPcap-based program (such as Wireshark, or TShark, or
1020 WinDump, or Analyzer, or...) since the machine was rebooted,
1021 you need to run that program from an account with administrator
1022 privileges; once you have run such a program, you will not need
1023 administrator privileges to run any such programs until you
1024 reboot.
1025 If you are running on Windows Windows XP or Windows Server 2003
1026 and have administrator privileges or a WinPcap-based program
1027 has been run with those privileges since the machine rebooted,
1028 this problem might clear up if you completely un-install
1029 WinPcap and then re-install it.
1030 If that doesn't work, then note that Wireshark relies on the
1031 WinPcap library, on the WinPcap device driver, and on the
1032 facilities that come with the OS on which it's running in order
1033 to do captures.
1034 Therefore, if the OS, the WinPcap library, or the WinPcap
1035 driver don't support capturing on a particular network
1036 interface device, Wireshark won't be able to capture on that
1037 device.
1038 WinPcap 2.3 has problems supporting PPP WAN interfaces on
1039 Windows NT 4.0, Windows 2000, Windows XP, and Windows Server
1040 2003, and, to avoid those problems, support for PPP WAN
1041 interfaces on those versions of Windows has been disabled in
1042 WinPcap 3.0. Regular dial-up lines, ISDN lines, ADSL
1043 connections using PPPoE or PPPoA, and various other lines such
1044 as T1/E1 lines are all PPP interfaces, so those interfaces
1045 might not show up on the list of interfaces in the "Capture
1046 Options" dialog on those OSes.
1047 On Windows 2000, Windows XP, and Windows Server 2003, but not
1048 Windows NT 4.0 or Windows Vista Beta 1, you should be able to
1049 capture on the "GenericDialupAdapter" with WinPcap 3.1. (3.1
1050 beta releases called it the "NdisWanAdapter"; if you're using a
1051 3.1 beta release, you should un-install it and install the
1052 final 3.1 release.) See the Wireshark Wiki item on PPP
1053 capturing for details.
1054 WinPcap prior to 3.0 does not support multiprocessor machines
1055 (note that machines with a single multi-threaded processor,
1056 such as Intel's new multi-threaded x86 processors, are
1057 multiprocessor machines as far as the OS and WinPcap are
1058 concerned), and recent 2.x versions of WinPcap refuse to
1059 operate if they detect that they're running on a multiprocessor
1060 machine, which means that they may not show any network
1061 interfaces. You will need to use WinPcap 3.0 to capture on a
1062 multiprocessor machine.
1063 If an interface doesn't show up in the list of interfaces in
1064 the "Interface:" field, and you know the name of the interface,
1065 try entering that name in the "Interface:" field and capturing
1066 on that device.
1067 If the attempt to capture on it succeeds, the interface is
1068 somehow not being reported by the mechanism Wireshark uses to
1069 get a list of interfaces. Try listing the interfaces with
1070 WinDump; see the WinDump Web site for information on using
1071 WinDump.
1072 You would run WinDump with the -D flag; if it lists the
1073 interface, please report this to wireshark-dev@wireshark.org
1074 giving full details of the problem, including
1075  
1076 * the operating system you're using, and the version of that
1077 operating system;
1078 * the type of network device you're using;
1079 * the output of WinDump.
1080  
1081 If WinDump does not list the interface, this is almost
1082 certainly a problem with one or more of:
1083  
1084 * the operating system you're using;
1085 * the device driver for the interface you're using;
1086 * the WinPcap library and/or the WinPcap device driver;
1087  
1088 so first check the WinPcap FAQ to see if your problem is
1089 mentioned there. If not, then see the WinPcap support page -
1090 check the "Submitting bugs" section.
1091 If you are having trouble capturing on a particular network
1092 interface, first try capturing on that device with WinDump; see
1093 the WinDump Web site for information on using WinDump.
1094 If you can capture on the interface with WinDump, send mail to
1095 wireshark-users@wireshark.org giving full details of the
1096 problem, including
1097  
1098 * the operating system you're using, and the version of that
1099 operating system;
1100 * the type of network device you're using;
1101 * the error message you get from Wireshark.
1102  
1103 If you cannot capture on the interface with WinDump, this is
1104 almost certainly a problem with one or more of:
1105  
1106 * the operating system you're using;
1107 * the device driver for the interface you're using;
1108 * the WinPcap library and/or the WinPcap device driver;
1109  
1110 so first check the WinPcap FAQ to see if your problem is
1111 mentioned there. If not, then see the WinPcap support page -
1112 check the "Submitting bugs" section.
1113 You may also want to ask the wireshark-users@wireshark.org and
1114 the winpcap-users@winpcap.org mailing lists to see if anybody
1115 happens to know about the problem and know a workaround or fix
1116 for the problem. (Note that you will have to subscribe to that
1117 list in order to be allowed to mail to it; see the WinPcap
1118 support page for information on the mailing list.) In your
1119 mail, please give full details of the problem, as described
1120 above, and also indicate that the problem occurs with WinDump,
1121 not just with Wireshark.
1122  
1123 Q 7.2: I'm running Wireshark on Windows; why do no network
1124 interfaces show up in the list of interfaces in the
1125 "Interface:" field in the dialog box popped up by
1126 "Capture->Start"?
1127  
1128 A: This is really the same question as a previous one; see the
1129 response to that question.
1130  
1131 Q 7.3: I'm running Wireshark on Windows; why doesn't my serial
1132 port/ADSL modem/ISDN modem show up in the list of interfaces in
1133 the "Interface:" field in the dialog box popped up by
1134 "Capture->Start"?
1135  
1136 A: Internet access on those devices is often done with the
1137 Point-to-Point (PPP) protocol; WinPcap 2.3 has problems
1138 supporting PPP WAN interfaces on Windows NT 4.0, Windows 2000,
1139 Windows XP, and Windows Server 2003, and, to avoid those
1140 problems, support for PPP WAN interfaces on those versions of
1141 Windows has been disabled in WinPcap 3.0.
1142 On Windows 2000, Windows XP, and Windows Server 2003, but not
1143 Windows NT 4.0 or Windows Vista Beta 1, you should be able to
1144 capture on the "GenericDialupAdapter" with WinPcap 3.1. (3.1
1145 beta releases called it the "NdisWanAdapter"; if you're using a
1146 3.1 beta release, you should un-install it and install the
1147 final 3.1 release.) See the Wireshark Wiki item on PPP
1148 capturing for details.
1149  
1150 Q 7.4: I'm running Wireshark on Windows NT 4.0/Windows
1151 2000/Windows XP/Windows Server 2003; my machine has a PPP
1152 (dial-up POTS, ISDN, etc.) interface, and it shows up in the
1153 "Interface" item in the "Capture Options" dialog box. Why can
1154 no packets be sent on or received from that network while I'm
1155 trying to capture traffic on that interface?
1156  
1157 A: Some versions of WinPcap have problems with PPP WAN
1158 interfaces on Windows NT 4.0, Windows 2000, Windows XP, and
1159 Windows Server 2003; one symptom that may be seen is that
1160 attempts to capture in promiscuous mode on the interface cause
1161 the interface to be incapable of sending or receiving packets.
1162 You can disable promiscuous mode using the -p command-line flag
1163 or the item in the "Capture Preferences" dialog box, but this
1164 may mean that outgoing packets, or incoming packets, won't be
1165 seen in the capture.
1166 On Windows 2000, Windows XP, and Windows Server 2003, but not
1167 Windows NT 4.0 or Windows Vista Beta 1, you should be able to
1168 capture on the "GenericDialupAdapter" with WinPcap 3.1. (3.1
1169 beta releases called it the "NdisWanAdapter"; if you're using a
1170 3.1 beta release, you should un-install it and install the
1171 final 3.1 release.) See the Wireshark Wiki item on PPP
1172 capturing for details.
1173  
1174 Q 7.5: I'm running Wireshark on Windows; why am I not seeing
1175 any traffic being sent by the machine running Wireshark?
1176  
1177 A: If you are running some form of VPN client software, it
1178 might be causing this problem; people have seen this problem
1179 when they have Check Point's VPN software installed on their
1180 machine. If that's the cause of the problem, you will have to
1181 remove the VPN software in order to have Wireshark (or any
1182 other application using WinPcap) see outgoing packets;
1183 unfortunately, neither we nor the WinPcap developers know any
1184 way to make WinPcap and the VPN software work well together.
1185 Also, some drivers for Windows (especially some wireless
1186 network interface drivers) apparently do not, when running in
1187 promiscuous mode, arrange that outgoing packets are delivered
1188 to the software that requested that the interface run
1189 promiscuously; try turning promiscuous mode off.
1190  
1191 Q 7.6: When I capture on Windows in promiscuous mode, I can see
1192 packets other than those sent to or from my machine; however,
1193 those packets show up with a "Short Frame" indication, unlike
1194 packets to or from my machine. What should I do to arrange that
1195 I see those packets in their entirety?
1196  
1197 A: In at least some cases, this appears to be the result of
1198 PGPnet running on the network interface on which you're
1199 capturing; turn it off on that interface.
1200  
1201 Q 7.7: I'm trying to capture 802.11 traffic on Windows; why am
1202 I not seeing any packets?
1203  
1204 A: At least some 802.11 card drivers on Windows appear not to
1205 see any packets if they're running in promiscuous mode. Try
1206 turning promiscuous mode off; you'll only be able to see
1207 packets sent by and received by your machine, not third-party
1208 traffic, and it'll look like Ethernet traffic and won't include
1209 any management or control frames, but that's a limitation of
1210 the card drivers.
1211 See the archived MicroLogix's list of cards supported with
1212 WinPcap for information on support of various adapters and
1213 drivers with WinPcap.
1214  
1215 Q 7.8: I'm trying to capture 802.11 traffic on Windows; why am
1216 I seeing packets received by the machine on which I'm capturing
1217 traffic, but not packets sent by that machine?
1218  
1219 A: This appears to be another problem with promiscuous mode;
1220 try turning it off.
1221  
1222 Q 7.9: I'm trying to capture Ethernet VLAN traffic on Windows,
1223 and I'm capturing on a "raw" Ethernet device rather than a
1224 "VLAN interface", so that I can see the VLAN headers; why am I
1225 seeing packets received by the machine on which I'm capturing
1226 traffic, but not packets sent by that machine?
1227  
1228 A: The way the Windows networking code works probably means
1229 that packets are sent on a "VLAN interface" rather than the
1230 "raw" device, so packets sent by the machine will only be seen
1231 when you capture on the "VLAN interface". If so, you will be
1232 unable to see outgoing packets when capturing on the "raw"
1233 device, so you are stuck with a choice between seeing VLAN
1234 headers and seeing outgoing packets.
1235  
1236 8. Capturing packets on UN*Xes
1237  
1238 Q 8.1: I'm running Wireshark on a UNIX-flavored OS; why does
1239 some network interface on my machine not show up in the list of
1240 interfaces in the "Interface:" field in the dialog box popped
1241 up by "Capture->Start", and/or why does Wireshark give me an
1242 error if I try to capture on that interface?
1243  
1244 A: You may need to run Wireshark from an account with
1245 sufficient privileges to capture packets, such as the
1246 super-user account, or may need to give your account sufficient
1247 privileges to capture packets. Only those interfaces that
1248 Wireshark can open for capturing show up in that list; if you
1249 don't have sufficient privileges to capture on any interfaces,
1250 no interfaces will show up in the list. See the Wireshark Wiki
1251 item on capture privileges for details on how to give a
1252 particular account or account group capture privileges on
1253 platforms where that can be done.
1254 If you are running Wireshark from an account with sufficient
1255 privileges, then note that Wireshark relies on the libpcap
1256 library, and on the facilities that come with the OS on which
1257 it's running in order to do captures. On some OSes, those
1258 facilities aren't present by default; see the Wireshark Wiki
1259 item on adding capture support for details.
1260 And, even if you're running with an account that has sufficient
1261 privileges to capture, and capture support is present in your
1262 OS, if the OS or the libpcap library don't support capturing on
1263 a particular network interface device or particular types of
1264 devices, Wireshark won't be able to capture on that device.
1265 On Solaris, note that libpcap 0.6.2 and earlier didn't support
1266 Token Ring interfaces; the current version, 0.7.2, does support
1267 Token Ring, and the current version of Wireshark works with
1268 libpcap 0.7.2 and later.
1269 If an interface doesn't show up in the list of interfaces in
1270 the "Interface:" field, and you know the name of the interface,
1271 try entering that name in the "Interface:" field and capturing
1272 on that device.
1273 If the attempt to capture on it succeeds, the interface is
1274 somehow not being reported by the mechanism Wireshark uses to
1275 get a list of interfaces; please report this to
1276 wireshark-dev@wireshark.org giving full details of the problem,
1277 including
1278  
1279 * the operating system you're using, and the version of that
1280 operating system (for Linux, give both the version number
1281 of the kernel and the name and version number of the
1282 distribution you're using);
1283 * the type of network device you're using.
1284  
1285 If you are having trouble capturing on a particular network
1286 interface, and you've made sure that (on platforms that require
1287 it) you've arranged that packet capture support is present, as
1288 per the above, first try capturing on that device with tcpdump.
1289 If you can capture on the interface with tcpdump, send mail to
1290 wireshark-users@wireshark.org giving full details of the
1291 problem, including
1292  
1293 * the operating system you're using, and the version of that
1294 operating system (for Linux, give both the version number
1295 of the kernel and the name and version number of the
1296 distribution you're using);
1297 * the type of network device you're using;
1298 * the error message you get from Wireshark.
1299  
1300 If you cannot capture on the interface with tcpdump, this is
1301 almost certainly a problem with one or more of:
1302  
1303 * the operating system you're using;
1304 * the device driver for the interface you're using;
1305 * the libpcap library;
1306  
1307 so you should report the problem to the company or organization
1308 that produces the OS (in the case of a Linux distribution,
1309 report the problem to whoever produces the distribution).
1310 You may also want to ask the wireshark-users@wireshark.org and
1311 the tcpdump-workers@lists.tcpdump.org mailing lists to see if
1312 anybody happens to know about the problem and know a workaround
1313 or fix for the problem. In your mail, please give full details
1314 of the problem, as described above, and also indicate that the
1315 problem occurs with tcpdump not just with Wireshark.
1316  
1317 Q 8.2: I'm running Wireshark on a UNIX-flavored OS; why do no
1318 network interfaces show up in the list of interfaces in the
1319 "Interface:" field in the dialog box popped up by
1320 "Capture->Start"?
1321  
1322 A: This is really the same question as the previous one; see
1323 the response to that question.
1324  
1325 Q 8.3: I'm capturing packets on Linux; why do the time stamps
1326 have only 100ms resolution, rather than 1us resolution?
1327  
1328 A: Wireshark gets time stamps from libpcap/WinPcap, and
1329 libpcap/WinPcap get them from the OS kernel, so Wireshark - and
1330 any other program using libpcap, such as tcpdump - is at the
1331 mercy of the time stamping code in the OS for time stamps.
1332 At least on x86-based machines, Linux can get high-resolution
1333 time stamps on newer processors with the Time Stamp Counter
1334 (TSC) register; for example, Intel x86 processors, starting
1335 with the Pentium Pro, and including all x86 processors since
1336 then, have had a TSC, and other vendors probably added the TSC
1337 at some point to their families of x86 processors. The Linux
1338 kernel must be configured with the CONFIG_X86_TSC option
1339 enabled in order to use the TSC. Make sure this option is
1340 enabled in your kernel.
1341 In addition, some Linux distributions may have bugs in their
1342 versions of the kernel that cause packets not to be given
1343 high-resolution time stamps even if the TSC is enabled. See,
1344 for example, bug 61111 for Red Hat Linux 7.2. If your
1345 distribution has a bug such as this, you may have to run a
1346 standard kernel from kernel.org in order to get high-resolution
1347 time stamps.
1348  
1349 9. Capturing packets on wireless LANs
1350  
1351 Q 9.1: How can I capture raw 802.11 frames, including non-data
1352 (management, beacon) frames?
1353  
1354 A: That depends on the operating system on which you're
1355 running, and on the 802.11 interface on which you're capturing.
1356 This would probably require that you capture in promiscuous
1357 mode or in the mode called "monitor mode" or "RFMON mode". On
1358 some platforms, or with some cards, this might require that you
1359 capture in monitor mode - promiscuous mode might not be
1360 sufficient. If you want to capture traffic on networks other
1361 than the one with which you're associated, you will have to
1362 capture in monitor mode.
1363 Not all operating systems support capturing non-data packets
1364 and, even on operating systems that do support it, not all
1365 drivers, and thus not all interfaces, support it. Even on those
1366 that do, monitor mode might not be supported by the operating
1367 system or by the drivers for all interfaces.
1368 NOTE: an interface running in monitor mode will, on most if not
1369 all platforms, not be able to act as a regular network
1370 interface; putting it into monitor mode will, in effect, take
1371 your machine off of whatever network it's on as long as the
1372 interface is in monitor mode, allowing it only to passively
1373 capture packets.
1374 This means that you should disable name resolution when
1375 capturing in monitor mode; otherwise, when Wireshark (or
1376 TShark, or tcpdump) tries to display IP addresses as host
1377 names, it will probably block for a long time trying to resolve
1378 the name because it will not be able to communicate with any
1379 DNS or NIS servers.
1380 See the Wireshark Wiki item on 802.11 capturing for details.
1381  
1382 Q 9.2: How do I capture on an 802.11 device in monitor mode?
1383  
1384 A: Whether you will be able to capture in monitor mode depends
1385 on the operating system, adapter, and driver you're using. See
1386 the previous question for information on monitor mode,
1387 including a link to the Wireshark Wiki page that gives details
1388 on 802.11 capturing.
1389  
1390 10. Viewing traffic
1391  
1392 Q 10.1: Why am I seeing lots of packets with incorrect TCP
1393 checksums?
1394  
1395 A: If the packets that have incorrect TCP checksums are all
1396 being sent by the machine on which Wireshark is running, this
1397 is probably because the network interface on which you're
1398 capturing does TCP checksum offloading. That means that the TCP
1399 checksum is added to the packet by the network interface, not
1400 by the OS's TCP/IP stack; when capturing on an interface,
1401 packets being sent by the host on which you're capturing are
1402 directly handed to the capture interface by the OS, which means
1403 that they are handed to the capture interface without a TCP
1404 checksum being added to them.
1405 The only way to prevent this from happening would be to disable
1406 TCP checksum offloading, but
1407  
1408 1. that might not even be possible on some OSes;
1409 2. that could reduce networking performance significantly.
1410  
1411 However, you can disable the check that Wireshark does of the
1412 TCP checksum, so that it won't report any packets as having TCP
1413 checksum errors, and so that it won't refuse to do TCP
1414 reassembly due to a packet having an incorrect TCP checksum.
1415 That can be set as an Wireshark preference by selecting
1416 "Preferences" from the "Edit" menu, opening up the "Protocols"
1417 list in the left-hand pane of the "Preferences" dialog box,
1418 selecting "TCP", from that list, turning off the "Check the
1419 validity of the TCP checksum when possible" option, clicking
1420 "Save" if you want to save that setting in your preference
1421 file, and clicking "OK".
1422 It can also be set on the Wireshark or TShark command line with
1423 a -o tcp.check_checksum:false command-line flag, or manually
1424 set in your preferences file by adding a
1425 tcp.check_checksum:false line.
1426  
1427 Q 10.2: I've just installed Wireshark, and the traffic on my
1428 local LAN is boring. Where can I find more interesting
1429 captures?
1430  
1431 A: We have a collection of strange and exotic sample capture
1432 files at https://wiki.wireshark.org/SampleCaptures
1433  
1434 Q 10.3: Why doesn't Wireshark correctly identify RTP packets?
1435 It shows them only as UDP.
1436  
1437 A: Wireshark can identify a UDP datagram as containing a packet
1438 of a particular protocol running atop UDP only if
1439  
1440 1. The protocol in question has a particular standard port
1441 number, and the UDP source or destination port number is
1442 that port
1443 2. Packets of that protocol can be identified by looking for a
1444 "signature" of some type in the packet - i.e., some data
1445 that, if Wireshark finds it in some particular part of a
1446 packet, means that the packet is almost certainly a packet
1447 of that type.
1448 3. Some other traffic earlier in the capture indicated that,
1449 for example, UDP traffic between two particular addresses
1450 and ports will be RTP traffic.
1451  
1452 RTP doesn't have a standard port number, so 1) doesn't work; it
1453 doesn't, as far as I know, have any "signature", so 2) doesn't
1454 work.
1455 That leaves 3). If there's RTSP traffic that sets up an RTP
1456 session, then, at least in some cases, the RTSP dissector will
1457 set things up so that subsequent RTP traffic will be
1458 identified. Currently, that's the only place we do that; there
1459 may be other places.
1460 However, there will always be places where Wireshark is simply
1461 incapable of deducing that a given UDP flow is RTP; a mechanism
1462 would be needed to allow the user to specify that a given
1463 conversation should be treated as RTP. As of Wireshark 0.8.16,
1464 such a mechanism exists; if you select a UDP or TCP packet, the
1465 right mouse button menu will have a "Decode As..." menu item,
1466 which will pop up a dialog box letting you specify that the
1467 source port, the destination port, or both the source and
1468 destination ports of the packet should be dissected as some
1469 particular protocol.
1470  
1471 Q 10.4: Why doesn't Wireshark show Yahoo Messenger packets in
1472 captures that contain Yahoo Messenger traffic?
1473  
1474 A: Wireshark only recognizes as Yahoo Messenger traffic packets
1475 to or from TCP port 3050 that begin with "YPNS", "YHOO", or
1476 "YMSG". TCP segments that start with the middle of a Yahoo
1477 Messenger packet that takes more than one TCP segment will not
1478 be recognized as Yahoo Messenger packets (even if the TCP
1479 segment also contains the beginning of another Yahoo Messenger
1480 packet).
1481  
1482 11. Filtering traffic
1483  
1484 Q 11.1: I saved a filter and tried to use its name to filter
1485 the display; why do I get an "Unexpected end of filter string"
1486 error?
1487  
1488 A: You cannot use the name of a saved display filter as a
1489 filter. To filter the display, you can enter a display filter
1490 expression - not the name of a saved display filter - in the
1491 "Filter:" box at the bottom of the display, and type the
1492 <Enter> key or press the "Apply" button (that does not require
1493 you to have a saved filter), or, if you want to use a saved
1494 filter, you can press the "Filter:" button, select the filter
1495 in the dialog box that pops up, and press the "OK" button.
1496  
1497 Q 11.2: How can I search for, or filter, packets that have a
1498 particular string anywhere in them?
1499  
1500 A: If you want to do this when capturing, you can't. That's a
1501 feature that would be hard to implement in capture filters
1502 without changes to the capture filter code, which, on many
1503 platforms, is in the OS kernel and, on other platforms, is in
1504 the libpcap library.
1505 After capture, you can search for text by selecting Edit→Find
1506 Packet... and making sure String is selected. Alternately, you
1507 can use the "contains" display filter operator or "matches"
1508 operator if it's supported on your system.
1509  
1510 Q 11.3: How do I filter a capture to see traffic for virus XXX?
1511  
1512 A: For some viruses/worms there might be a capture filter to
1513 recognize the virus traffic. Check the CaptureFilters page on
1514 the Wireshark Wiki to see if anybody's added such a filter.
1515 Note that Wireshark was not designed to be an intrusion
1516 detection system; you might be able to use it as an IDS, but in
1517 most cases software designed to be an IDS, such as Snort or
1518 Prelude, will probably work better.
1519