forked from osmocom/wireshark
a2a5c2f998
svn path=/trunk/; revision=18979
1466 lines
72 KiB
Text
1466 lines
72 KiB
Text
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The Wireshark FAQ
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Note: This is just an ASCII snapshot of the faq and may not be up to
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date. Please go to http://www.wireshark.org/faq.html for the up
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to date version. The version of this snapshot can be found at
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the end of this document.
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INDEX
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1. General Questions:
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1.1 What is Wireshark?
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1.2 What's up with the name change? Is Wireshark a fork?
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1.3 Where can I get help?
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1.4 How much does Wireshark cost?
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1.5 Can I use Wireshark commercially?
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1.6 Can I use Wireshark as part of my commercial product?
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1.7 What protocols are currently supported?
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1.8 Are there any plans to support {your favorite protocol}?
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1.9 Can Wireshark read capture files from {your favorite network analyzer}?
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1.10 What devices can Wireshark use to capture packets?
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1.11 Does Wireshark work on Windows Me?
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1.12 Does Wireshark work on Windows XP?
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2. Downloading Wireshark:
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2.1 Why do I get an error when I try to run the Win32 installer?
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3. Installing Wireshark:
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3.1 I installed the Wireshark RPM (or other package); why did it install
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TShark but not Wireshark?
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4. Building Wireshark:
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4.1 I have libpcap installed; why did the configure script not find pcap.h
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or bpf.h?
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4.2 Why do I get the error
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dftest_DEPENDENCIES was already defined in condition TRUE, which implies
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condition HAVE_PLUGINS_TRUE
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when I try to build Wireshark from SVN or a SVN snapshot?
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4.3 Why does the linker fail with a number of "Output line too long."
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messages followed by linker errors when I try to buil Wireshark?
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4.4 When I try to build Wireshark on Solaris, why does the link fail
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complaining that plugin_list is undefined?
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4.5 When I try to build Wireshark on Windows, why does the build fail
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because of conflicts between winsock.h and winsock2.h?
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5. Starting Wireshark:
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5.1 Why does Wireshark crash with a Bus Error when I try to run it on
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Solaris 8?
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5.2 When I run Wireshark on Windows NT, why does it die with a Dr. Watson
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error, reporting an "Integer division by zero" exception, when I start it?
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5.3 When I try to run Wireshark, why does it complain about
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sprint_realloc_objid being undefined?
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5.4 When I try to run Wireshark on Windows, why does it fail to run with a
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complaint that it can't find packet.dll?
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5.5 I've installed Wireshark from Fink on Mac OS X; why is it very slow to
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start up?
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6. Crashes and other fatal errors:
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6.1 I have an XXX network card on my machine; if I try to capture on it, why
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does my machine crash or reset itself?
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6.2 Why does my machine crash or reset itself when I select "Start" from the
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"Capture" menu or select "Preferences" from the "Edit" menu?
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7. Capturing packets:
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7.1 When I use Wireshark to capture packets, why do I see only packets to
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and from my machine, or not see all the traffic I'm expecting to see from or
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to the machine I'm trying to monitor?
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7.2 When I capture with Wireshark, why can't I see any TCP packets other
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than packets to and from my machine, even though another analyzer on the
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network sees those packets?
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7.3 Why am I only seeing ARP packets when I try to capture traffic?
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7.4 Why am I not seeing any traffic when I try to capture traffic?
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7.5 Can Wireshark capture on (my T1/E1 line, SS7 links, etc.)?
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7.6 How do I put an interface into promiscuous mode?
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7.7 I can set a display filter just fine; why don't capture filters work?
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7.8 I'm entering valid capture filters; why do I still get "parse error"
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errors?
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7.9 How can I capture packets with CRC errors?
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7.10 How can I capture entire frames, including the FCS?
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7.11 I'm capturing packets on a machine on a VLAN; why don't the packets I'm
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capturing have VLAN tags?
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7.12 Why does Wireshark hang after I stop a capture?
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8. Capturing packets on Windows:
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8.1 I'm running Wireshark on Windows; why does some network interface on my
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machine not show up in the list of interfaces in the "Interface:" field in
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the dialog box popped up by "Capture->Start", and/or why does Wireshark give
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me an error if I try to capture on that interface?
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8.2 I'm running Wireshark on Windows; why do no network interfaces show up
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in the list of interfaces in the "Interface:" field in the dialog box popped
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up by "Capture->Start"?
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8.3 I'm running Wireshark on Windows; why doesn't my serial port/ADSL
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modem/ISDN modem show up in the list of interfaces in the "Interface:" field
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in the dialog box popped up by "Capture->Start"?
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8.4 I'm running Wireshark on Windows NT 4.0/Windows 2000/Windows XP/Windows
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Server 2003; my machine has a PPP (dial-up POTS, ISDN, etc.) interface, and
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it shows up in the "Interface" item in the "Capture Options" dialog box. Why
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can no packets be sent on or received from that network while I'm trying to
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capture traffic on that interface?
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8.5 I'm running Wireshark on Windows 95/98/Me, on a machine with more than
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one network adapter of the same type; why does Wireshark show all of those
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adapters with the same name, not letting me use any of those adapters other
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than the first one?
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8.6 I'm running Wireshark on Windows; why am I not seeing any traffic being
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sent by the machine running Wireshark?
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8.7 When I capture on Windows in promiscuous mode, I can see packets other
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than those sent to or from my machine; however, those packets show up with a
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"Short Frame" indication, unlike packets to or from my machine. What should
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I do to arrange that I see those packets in their entirety?
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8.8 I'm capturing packets on {Windows 95, Windows 98, Windows Me}; why are
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the time stamps on packets wrong?
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8.9 I'm trying to capture 802.11 traffic on Windows; why am I not seeing any
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packets?
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8.10 I'm trying to capture 802.11 traffic on Windows; why am I seeing
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packets received by the machine on which I'm capturing traffic, but not
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packets sent by that machine?
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8.11 I'm trying to capture Ethernet VLAN traffic on Windows, and I'm
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capturing on a "raw" Ethernet device rather than a "VLAN interface", so that
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I can see the VLAN headers; why am I seeing packets received by the machine
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on which I'm capturing traffic, but not packets sent by that machine?
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9. Capturing packets on UN*Xes:
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9.1 I'm running Wireshark on a UNIX-flavored OS; why does some network
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interface on my machine not show up in the list of interfaces in the
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"Interface:" field in the dialog box popped up by "Capture->Start", and/or
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why does Wireshark give me an error if I try to capture on that interface?
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9.2 I'm running Wireshark on a UNIX-flavored OS; why do no network
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interfaces show up in the list of interfaces in the "Interface:" field in
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the dialog box popped up by "Capture->Start"?
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9.3 I'm capturing packets on Linux; why do the time stamps have only 100ms
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resolution, rather than 1us resolution?
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10. Capturing packets on wireless LANs:
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10.1 How can I capture raw 802.11 frames, including non-data (management,
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beacon) frames?
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10.2 How do I capture on an 802.11 device in monitor mode?
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11. Viewing traffic:
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11.1 Why am I seeing lots of packets with incorrect TCP checksums?
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11.2 I've just installed Wireshark, and the traffic on my local LAN is
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boring. Where can I find more interesting captures?
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11.3 Why doesn't Wireshark correctly identify RTP packets? It shows them
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only as UDP.
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11.4 Why doesn't Wireshark show Yahoo Messenger packets in captures that
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contain Yahoo Messenger traffic?
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12. Filtering traffic:
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12.1 I saved a filter and tried to use its name to filter the display; why
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do I get an "Unexpected end of filter string" error?
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12.2 How can I search for, or filter, packets that have a particular string
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anywhere in them?
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12.3 How do I filter a capture to see traffic for virus XXX?
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1. General Questions
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Q 1.1: What is Wireshark?
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A: Gerald Combs, the creator of Ethereal®, has initiated the Wireshark
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network protocol analyzer project, a successor to Ethereal®. The Ethereal®
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core developer team has moved with Gerald to the Wireshark project. It is
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the world's most popular network protocol analyzer. It has a rich and
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powerful feature set, and runs on most computing platforms including
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Windows, OS X, and Linux. It is freely available as open source, and is
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released under the GNU General Public License.
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For more information, please see the About Wireshark page.
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Q 1.2: What's up with the name change? Is Wireshark a fork?
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A: In May of 2006, the original author of Ethereal® went to work for CACE
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Technologies (best known for WinPcap). Unfortunately, he had to leave the
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Ethereal® trademarks behind.
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This left the project in an awkward position. The only reasonable way to
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ensure the continued success of the project was to change the name. This is
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how Wireshark was born.
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Wireshark is almost (but not quite) a fork. Normally a "fork" of an open
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source project results in two names, web sites, development teams, support
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infrastructures, etc. This is the case with Wireshark except for one notable
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exception -- every member of the core development team is now working on
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Wireshark. More information on the name change can be found here:
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*
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*
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Q 1.3: Where can I get help?
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A: Community support is available on the wireshark-users mailing list.
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Subscription information and archives for all of Wireshark's mailing lists
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can be found at http://www.wireshark.org/mailman/listinfo. An IRC channel
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dedicated to Wireshark can be found at irc://irc.freenode.net/wireshark.
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Commercial support, training, and development services are available from
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CACE Technologies.
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Q 1.4: How much does Wireshark cost?
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A: Wireshark is "free software"; you can download it without paying any
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license fee. The version of Wireshark you download isn't a "demo" version,
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with limitations not present in a "full" version; it is the full version.
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The license under which Wireshark is issued is the GNU General Public
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License. See the GNU GPL FAQ for some more information.
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Q 1.5: Can I use Wireshark commercially?
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A: Yes, if, for example, you mean "I work for a commercial organization; can
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I use Wireshark to capture and analyze network traffic in our company's
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networks or in our customer's networks?"
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If you mean "Can I use Wireshark as part of my commercial product?", see the
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next entry in the FAQ.
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Q 1.6: Can I use Wireshark as part of my commercial product?
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A: As noted, Wireshark is licensed under the GNU General Public License. The
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GPL imposes conditions on your use of GPL'ed code in your own products; you
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cannot, for example, make a "derived work" from Wireshark, by making
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modifications to it, and then sell the resulting derived work and not allow
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recipients to give away the resulting work. You must also make the changes
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you've made to the Wireshark source available to all recipients of your
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modified version; those changes must also be licensed under the terms of the
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GPL. See the GPL FAQ for more details; in particular, note the answer to the
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question about modifying a GPLed program and selling it commercially, and
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the question about linking GPLed code with other code to make a proprietary
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program.
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You can combine a GPLed program such as Wireshark and a commercial program
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as long as they communicate "at arm's length", as per this item in the GPL
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FAQ.
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Q 1.7: What protocols are currently supported?
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A: There are currently hundreds of supported protocols and media. Details
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can be found in the wireshark(1) man page.
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Q 1.8: Are there any plans to support {your favorite protocol}?
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A: Support for particular protocols is added to Wireshark as a result of
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people contributing that support; no formal plans for adding support for
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particular protocols in particular future releases exist.
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Q 1.9: Can Wireshark read capture files from {your favorite network
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analyzer}?
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A: Support for particular protocols is added to Wireshark as a result of
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people contributing that support; no formal plans for adding support for
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particular protocols in particular future releases exist.
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If a network analyzer writes out files in a format already supported by
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Wireshark (e.g., in libpcap format), Wireshark may already be able to read
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them, unless the analyzer has added its own proprietary extensions to that
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format.
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If a network analyzer writes out files in its own format, or has added
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proprietary extensions to another format, in order to make Wireshark read
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captures from that network analyzer, we would either have to have a
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specification for the file format, or the extensions, sufficient to give us
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enough information to read the parts of the file relevant to Wireshark, or
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would need at least one capture file in that format AND a detailed textual
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analysis of the packets in that capture file (showing packet time stamps,
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packet lengths, and the top-level packet header) in order to
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reverse-engineer the file format.
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Note that there is no guarantee that we will be able to reverse-engineer a
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capture file format.
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Q 1.10: What devices can Wireshark use to capture packets?
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A: Wireshark can read live data from Ethernet, Token-Ring, FDDI, serial (PPP
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and SLIP) (if the OS on which it's running allows Wireshark to do so),
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802.11 wireless LAN (if the OS on which it's running allows Wireshark to do
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so), ATM connections (if the OS on which it's running allows Wireshark to do
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so), and the "any" device supported on Linux by recent versions of libpcap.
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It can also read a variety of capture file formats, including:
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* AG Group/WildPackets EtherPeek/TokenPeek/AiroPeek/EtherHelp/Packet
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Grabber captures
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* AIX's iptrace captures
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* Accellent's 5Views LAN agent output
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* Cinco Networks NetXRay captures
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* Cisco Secure Intrusion Detection System IPLog output
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* CoSine L2 debug output
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* DBS Etherwatch VMS text output
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* Endace Measurement Systems' ERF format captures
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* EyeSDN USB S0 traces
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* HP-UX nettl captures
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* ISDN4BSD project i4btrace captures
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* Linux Bluez Bluetooth stack hcidump -w traces
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* Lucent/Ascend router debug output
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* Microsoft Network Monitor captures
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* Network Associates Windows-based Sniffer captures
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* Network General/Network Associates DOS-based Sniffer (compressed or
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uncompressed) captures
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* Network Instruments Observer version 9 captures
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* Novell LANalyzer captures
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* RADCOM's WAN/LAN analyzer captures
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* Shomiti/Finisar Surveyor captures
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* Toshiba's ISDN routers dump output
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* VMS TCPIPtrace/TCPtrace/UCX$TRACE output
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* Visual Networks' Visual UpTime traffic capture
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* libpcap, tcpdump and various other tools using tcpdump's capture format
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* snoop and atmsnoop output
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so that it can read traces from various network types, as captured by other
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applications or equipment, even if it cannot itself capture on those network
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types.
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Q 1.11: Does Wireshark work on Windows Me?
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A: Yes, but if you want to capture packets, you will need to install the
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latest version of WinPcap, as 2.02 and earlier versions of WinPcap didn't
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support Windows Me. You should also install the latest version of Wireshark
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as well.
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Q 1.12: Does Wireshark work on Windows XP?
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A: Yes, but if you want to capture packets, you will need to install the
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latest version of WinPcap, as 2.2 and earlier versions of WinPcap didn't
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support Windows XP.
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2. Downloading Wireshark
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Q 2.1: Why do I get an error when I try to run the Win32 installer?
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A: The program you used to download it may have downloaded it incorrectly.
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Web browsers sometimes may do this.
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Try downloading it with, for example:
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* Wget, for which Windows binaries are available on the SunSITE FTP server
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at sunsite.tk or Heiko Herold's windows wget spot - wGetGUI offers a GUI
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interface that uses wget;
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* WS_FTP from Ipswitch,
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* the ftp command that comes with Windows.
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If you use the ftp command, make sure you do the transfer in binary mode
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rather than ASCII mode, by using the binary command before transferring the
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file.
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3. Installing Wireshark
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Q 3.1: I installed the Wireshark RPM (or other package); why did it install
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TShark but not Wireshark?
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A: Many distributions have separate Wireshark packages, one for non-GUI
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components such as TShark, editcap, dumpcap, etc. and one for the GUI. If
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this is the case on your system, there's probably a separate package named
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wireshark-gnome or wireshark-gtk+. Find it and install it.
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4. Building Wireshark
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Q 4.1: I have libpcap installed; why did the configure script not find
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pcap.h or bpf.h?
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A: Are you sure pcap.h and bpf.h are installed? The official distribution of
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libpcap only installs the libpcap.a library file when "make install" is run.
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To install pcap.h and bpf.h, you must run "make install-incl". If you're
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running Debian or Redhat, make sure you have the "libpcap-dev" or
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"libpcap-devel" packages installed.
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It's also possible that pcap.h and bpf.h have been installed in a strange
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location. If this is the case, you may have to tweak aclocal.m4.
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Q 4.2: Why do I get the error
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dftest_DEPENDENCIES was already defined in condition TRUE, which implies
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condition HAVE_PLUGINS_TRUE
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when I try to build Wireshark from SVN or a SVN snapshot?
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A: You probably have automake 1.5 installed on your machine (the command
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automake --version will report the version of automake on your machine).
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There is a bug in that version of automake that causes this problem; upgrade
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to a later version of automake (1.6 or later).
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Q 4.3: Why does the linker fail with a number of "Output line too long."
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messages followed by linker errors when I try to buil Wireshark?
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A: The version of the sed command on your system is incapable of handling
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very long lines. On Solaris, for example, /usr/bin/sed has a line length
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limit too low to allow libtool to work; /usr/xpg4/bin/sed can handle it, as
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can GNU sed if you have it installed.
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On Solaris, changing your command search path to search /usr/xpg4/bin before
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/usr/bin should make the problem go away; on any platform on which you have
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this problem, installing GNU sed and changing your command path to search
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the directory in which it is installed before searching the directory with
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the version of sed that came with the OS should make the problem go away.
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Q 4.4: When I try to build Wireshark on Solaris, why does the link fail
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complaining that plugin_list is undefined?
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A: This appears to be due to a problem with some versions of the GTK+ and
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GLib packages from www.sunfreeware.org; un-install those packages, and try
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getting the 1.2.10 versions from that site, or the versions from The Written
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Word, or the versions from Sun's GNOME distribution, or the versions from
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the supplemental software CD that comes with the Solaris media kit, or build
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them from source from the GTK Web site. Then re-run the configuration
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script, and try rebuilding Wireshark. (If you get the 1.2.10 versions from
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www.sunfreeware.org, and the problem persists, un-install them and try
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installing one of the other versions mentioned.)
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|
|
Q 4.5: When I try to build Wireshark on Windows, why does the build fail
|
|
because of conflicts between winsock.h and winsock2.h?
|
|
|
|
A: As of Wireshark 0.9.5, you must install WinPcap 2.3 or later, and the
|
|
corresponding version of the developer's pack, in order to be able to
|
|
compile Wireshark; it will not compile with older versions of the
|
|
developer's pack. The symptoms of this failure are conflicts between
|
|
definitions in winsock.h and in winsock2.h; Wireshark uses winsock2.h, but
|
|
pre-2.3 versions of the WinPcap developer's packet use winsock.h. (2.3 uses
|
|
winsock2.h, so if Wireshark were to use winsock.h, it would not be able to
|
|
build with current versions of the WinPcap developer's pack.)
|
|
|
|
Note that the installed version of the developer's pack should be the same
|
|
version as the version of WinPcap you have installed.
|
|
|
|
5. Starting Wireshark
|
|
|
|
Q 5.1: Why does Wireshark crash with a Bus Error when I try to run it on
|
|
Solaris 8?
|
|
|
|
A: Some versions of the GTK+ library from www.sunfreeware.org appear to be
|
|
buggy, causing Wireshark to drop core with a Bus Error. Un-install those
|
|
packages, and try getting the 1.2.10 version from that site, or the version
|
|
from The Written Word, or the version from Sun's GNOME distribution, or the
|
|
version from the supplemental software CD that comes with the Solaris media
|
|
kit, or build it from source from the GTK Web site. Update the GLib library
|
|
to the 1.2.10 version, from the same source, as well. (If you get the 1.2.10
|
|
versions from www.sunfreeware.org, and the problem persists, un-install them
|
|
and try installing one of the other versions mentioned.)
|
|
|
|
Similar problems may exist with older versions of GTK+ for earlier versions
|
|
of Solaris.
|
|
|
|
Q 5.2: When I run Wireshark on Windows NT, why does it die with a Dr. Watson
|
|
error, reporting an "Integer division by zero" exception, when I start it?
|
|
|
|
A: In at least some case, this appears to be due to using the default VGA
|
|
driver; if that's not the correct driver for your video card, try running
|
|
the correct driver for your video card.
|
|
|
|
Q 5.3: When I try to run Wireshark, why does it complain about
|
|
sprint_realloc_objid being undefined?
|
|
|
|
A: Wireshark can only be linked with version 4.2.2 or later of UCD SNMP.
|
|
Your version of Wireshark was dynamically linked with such a version of UCD
|
|
SNMP; however, you have an older version of UCD SNMP installed, which means
|
|
that when Wireshark is run, it tries to link to the older version, and
|
|
fails. You will have to replace that version of UCD SNMP with version 4.2.2
|
|
or a later version.
|
|
|
|
Q 5.4: When I try to run Wireshark on Windows, why does it fail to run with
|
|
a complaint that it can't find packet.dll?
|
|
|
|
A: In older versions of Wireshark, there were two binary distributions
|
|
available for Windows, one that supported capturing packets, and one that
|
|
didn't. The version that supported capturing packets required that you
|
|
install the WinPcap driver; if you didn't install it, it would fail to run
|
|
because it couldn't find packet.dll.
|
|
|
|
The current version of Wireshark has only one binary distribution for
|
|
Windows; that version will check whether WinPcap is installed and, if it's
|
|
not, will disable support for packet capture.
|
|
|
|
The WinPcap driver and libraries can be downloaded from the WinPcap Web site
|
|
or the Wiretapped.net mirror of the WinPcap site.
|
|
|
|
Q 5.5: I've installed Wireshark from Fink on Mac OS X; why is it very slow
|
|
to start up?
|
|
|
|
A: When an application is installed on OS X, prior to 10.4, it is usually
|
|
"prebound" to speed up launching the application. (That's what the
|
|
"Optimizing" phase of installation is.) Fink normally performs prebinding
|
|
automatically when you install a package. However, in some rare cases, for
|
|
whatever reason the prebinding caches get corrupt, and then not only does
|
|
prebinding fail, but startup actually becomes much slower, because the
|
|
system tries in vain to perform prebinding "on the fly" as you launch the
|
|
application. This fails, causing sometimes huge delays. To fix the
|
|
prebinding caches, run the command
|
|
sudo /sw/var/lib/fink/prebound/update-package-prebinding.pl -f
|
|
|
|
6. Crashes and other fatal errors
|
|
|
|
Q 6.1: I have an XXX network card on my machine; if I try to capture on it,
|
|
why does my machine crash or reset itself?
|
|
|
|
A: This is almost certainly a problem with one or more of:
|
|
* the operating system you're using;
|
|
* the device driver for the interface you're using;
|
|
* the libpcap/WinPcap library and, if this is Windows, the WinPcap device
|
|
driver;
|
|
|
|
so:
|
|
* if you are using Windows, see the WinPcap support page - check the
|
|
"Submitting bugs" section;
|
|
* if you are using some Linux distribution, some version of BSD, or some
|
|
other UNIX-flavored OS, you should report the problem to the company or
|
|
organization that produces the OS (in the case of a Linux distribution,
|
|
report the problem to whoever produces the distribution).
|
|
|
|
Q 6.2: Why does my machine crash or reset itself when I select "Start" from
|
|
the "Capture" menu or select "Preferences" from the "Edit" menu?
|
|
|
|
A: Both of those operations cause Wireshark to try to build a list of the
|
|
interfaces that it can open; it does so by getting a list of interfaces and
|
|
trying to open them. There is probably an OS, driver, or, for Windows,
|
|
WinPcap bug that causes the system to crash when this happens; see the
|
|
previous question.
|
|
|
|
7. Capturing packets
|
|
|
|
Q 7.1: When I use Wireshark to capture packets, why do I see only packets to
|
|
and from my machine, or not see all the traffic I'm expecting to see from or
|
|
to the machine I'm trying to monitor?
|
|
|
|
A: This might be because the interface on which you're capturing is plugged
|
|
into an Ethernet or Token Ring switch; on a switched network, unicast
|
|
traffic between two ports will not necessarily appear on other ports - only
|
|
broadcast and multicast traffic will be sent to all ports.
|
|
|
|
Note that even if your machine is plugged into a hub, the "hub" may be a
|
|
switched hub, in which case you're still on a switched network.
|
|
|
|
Note also that on the Linksys Web site, they say that their auto-sensing
|
|
hubs "broadcast the 10Mb packets to the port that operate at 10Mb only and
|
|
broadcast the 100Mb packets to the ports that operate at 100Mb only", which
|
|
would indicate that if you sniff on a 10Mb port, you will not see traffic
|
|
coming sent to a 100Mb port, and vice versa. This problem has also been
|
|
reported for Netgear dual-speed hubs, and may exist for other "auto-sensing"
|
|
or "dual-speed" hubs.
|
|
|
|
Some switches have the ability to replicate all traffic on all ports to a
|
|
single port so that you can plug your analyzer into that single port to
|
|
sniff all traffic. You would have to check the documentation for the switch
|
|
to see if this is possible and, if so, to see how to do this. See the switch
|
|
reference page on the Wireshark Wiki for information on some switches. (Note
|
|
that it's a Wiki, so you can update or fix that information, or add
|
|
additional information on those switches or information on new switches,
|
|
yourself.)
|
|
|
|
Note also that many firewall/NAT boxes have a switch built into them; this
|
|
includes many of the "cable/DSL router" boxes. If you have a box of that
|
|
sort, that has a switch with some number of Ethernet ports into which you
|
|
plug machines on your network, and another Ethernet port used to connect to
|
|
a cable or DSL modem, you can, at least, sniff traffic between the machines
|
|
on your network and the Internet by plugging the Ethernet port on the router
|
|
going to the modem, the Ethernet port on the modem, and the machine on which
|
|
you're running Wireshark into a hub (make sure it's not a switching hub, and
|
|
that, if it's a dual-speed hub, all three of those ports are running at the
|
|
same speed.
|
|
|
|
If your machine is not plugged into a switched network or a dual-speed hub,
|
|
or it is plugged into a switched network but the port is set up to have all
|
|
traffic replicated to it, the problem might be that the network interface on
|
|
which you're capturing doesn't support "promiscuous" mode, or because your
|
|
OS can't put the interface into promiscuous mode. Normally, network
|
|
interfaces supply to the host only:
|
|
* packets sent to one of that host's link-layer addresses;
|
|
* broadcast packets;
|
|
* multicast packets sent to a multicast address that the host has
|
|
configured the interface to accept.
|
|
|
|
Most network interfaces can also be put in "promiscuous" mode, in which they
|
|
supply to the host all network packets they see. Wireshark will try to put
|
|
the interface on which it's capturing into promiscuous mode unless the
|
|
"Capture packets in promiscuous mode" option is turned off in the "Capture
|
|
Options" dialog box, and TShark will try to put the interface on which it's
|
|
capturing into promiscuous mode unless the -p option was specified. However,
|
|
some network interfaces don't support promiscuous mode, and some OSes might
|
|
not allow interfaces to be put into promiscuous mode.
|
|
|
|
If the interface is not running in promiscuous mode, it won't see any
|
|
traffic that isn't intended to be seen by your machine. It will see
|
|
broadcast packets, and multicast packets sent to a multicast MAC address the
|
|
interface is set up to receive.
|
|
|
|
You should ask the vendor of your network interface whether it supports
|
|
promiscuous mode. If it does, you should ask whoever supplied the driver for
|
|
the interface (the vendor, or the supplier of the OS you're running on your
|
|
machine) whether it supports promiscuous mode with that network interface.
|
|
|
|
In the case of token ring interfaces, the drivers for some of them, on
|
|
Windows, may require you to enable promiscuous mode in order to capture in
|
|
promiscuous mode. See the Wireshark Wiki item on Token Ring capturing for
|
|
details.
|
|
|
|
In the case of wireless LAN interfaces, it appears that, when those
|
|
interfaces are promiscuously sniffing, they're running in a significantly
|
|
different mode from the mode that they run in when they're just acting as
|
|
network interfaces (to the extent that it would be a significant effor for
|
|
those drivers to support for promiscuously sniffing and acting as regular
|
|
network interfaces at the same time), so it may be that Windows drivers for
|
|
those interfaces don't support promiscuous mode.
|
|
|
|
Q 7.2: When I capture with Wireshark, why can't I see any TCP packets other
|
|
than packets to and from my machine, even though another analyzer on the
|
|
network sees those packets?
|
|
|
|
A: You're probably not seeing any packets other than unicast packets to or
|
|
from your machine, and broadcast and multicast packets; a switch will
|
|
normally send to a port only unicast traffic sent to the MAC address for the
|
|
interface on that port, and broadcast and multicast traffic - it won't send
|
|
to that port unicast traffic sent to a MAC address for some other interface
|
|
- and a network interface not in promiscuous mode will receive only unicast
|
|
traffic sent to the MAC address for that interface, broadcast traffic, and
|
|
multicast traffic sent to a multicast MAC address the interface is set up to
|
|
receive.
|
|
|
|
TCP doesn't use broadcast or multicast, so you will only see your own TCP
|
|
traffic, but UDP services may use broadcast or multicast so you'll see some
|
|
UDP traffic - however, this is not a problem with TCP traffic, it's a
|
|
problem with unicast traffic, as you also won't see all UDP traffic between
|
|
other machines.
|
|
|
|
I.e., this is probably the same question as this earlier one; see the
|
|
response to that question.
|
|
|
|
Q 7.3: Why am I only seeing ARP packets when I try to capture traffic?
|
|
|
|
A: You're probably on a switched network, and running Wireshark on a machine
|
|
that's not sending traffic to the switch and not being sent any traffic from
|
|
other machines on the switch. ARP packets are often broadcast packets, which
|
|
are sent to all switch ports.
|
|
|
|
I.e., this is probably the same question as this earlier one; see the
|
|
response to that question.
|
|
|
|
Q 7.4: Why am I not seeing any traffic when I try to capture traffic?
|
|
|
|
A: Is the machine running Wireshark sending out any traffic on the network
|
|
interface on which you're capturing, or receiving any traffic on that
|
|
network, or is there any broadcast traffic on the network or multicast
|
|
traffic to a multicast group to which the machine running Wireshark belongs?
|
|
|
|
If not, this may just be a problem with promiscuous sniffing, either due to
|
|
running on a switched network or a dual-speed hub, or due to problems with
|
|
the interface not supporting promiscuous mode; see the response to this
|
|
earlier question.
|
|
|
|
Otherwise, on Windows, see the response to this question and, on a
|
|
UNIX-flavored OS, see the response to this question.
|
|
|
|
Q 7.5: Can Wireshark capture on (my T1/E1 line, SS7 links, etc.)?
|
|
|
|
A: Wireshark can only capture on devices supported by libpcap/WinPcap. On
|
|
most OSes, only devices that can act as network interfaces of the type that
|
|
support IP are supported as capture devices for libpcap/WinPcap, although
|
|
the device doesn't necessarily have to be running as an IP interface in
|
|
order to support traffic capture.
|
|
|
|
On Linux and FreeBSD, libpcap 0.8 and later support the API for Endace
|
|
Measurement Systems' DAG cards, so that a system with one of those cards,
|
|
and its driver and libraries, installed can capture traffic with those cards
|
|
with libpcap-based applications. You would either have to have a version of
|
|
Wireshark built with that version of libpcap, or a dynamically-linked
|
|
version of Wireshark and a shared libpcap library with DAG support, in order
|
|
to do so with Wireshark. You should ask Endace whether that could be used to
|
|
capture traffic on, for example, your T1/E1 link. See the SS7 capture setup
|
|
page on the Wireshark Wiki for current information on capturing SS7 traffic
|
|
on TDM links.
|
|
|
|
Q 7.6: How do I put an interface into promiscuous mode?
|
|
|
|
A: By not disabling promiscuous mode when running Wireshark or TShark.
|
|
|
|
Note, however, that:
|
|
* the form of promiscuous mode that libpcap (the library that programs
|
|
such as tcpdump, Wireshark, etc. use to do packet capture) turns on will
|
|
not necessarily be shown if you run ifconfig on the interface on a UNIX
|
|
system;
|
|
* some network interfaces might not support promiscuous mode, and some
|
|
drivers might not allow promiscuous mode to be turned on - see this
|
|
earlier question for more information on that;
|
|
* the fact that you're not seeing any traffic, or are only seeing
|
|
broadcast traffic, or aren't seeing any non-broadcast traffic other than
|
|
traffic to or from the machine running Wireshark, does not mean that
|
|
promiscuous mode isn't on - see this earlier question for more
|
|
information on that.
|
|
|
|
I.e., this is probably the same question as this earlier one; see the
|
|
response to that question.
|
|
|
|
Q 7.7: I can set a display filter just fine; why don't capture filters work?
|
|
|
|
A: Capture filters currently use a different syntax than display filters.
|
|
Here's the corresponding section from the wireshark(1) man page:
|
|
|
|
"Display filters in Wireshark are very powerful; more fields are filterable
|
|
in Wireshark than in other protocol analyzers, and the syntax you can use to
|
|
create your filters is richer. As Wireshark progresses, expect more and more
|
|
protocol fields to be allowed in display filters.
|
|
|
|
Packet capturing is performed with the pcap library. The capture filter
|
|
syntax follows the rules of the pcap library. This syntax is different from
|
|
the display filter syntax."
|
|
|
|
The capture filter syntax used by libpcap can be found in the tcpdump(8) man
|
|
page.
|
|
|
|
Q 7.8: I'm entering valid capture filters; why do I still get "parse error"
|
|
errors?
|
|
|
|
A: There is a bug in some versions of libpcap/WinPcap that cause it to
|
|
report parse errors even for valid expressions if a previous filter
|
|
expression was invalid and got a parse error.
|
|
|
|
Try exiting and restarting Wireshark; if you are using a version of
|
|
libpcap/WinPcap with this bug, this will "erase" its memory of the previous
|
|
parse error. If the capture filter that got the "parse error" now works, the
|
|
earlier error with that filter was probably due to this bug.
|
|
|
|
The bug was fixed in libpcap 0.6; 0.4[.x] and 0.5[.x] versions of libpcap
|
|
have this bug, but 0.6[.x] and later versions don't.
|
|
|
|
Versions of WinPcap prior to 2.3 are based on pre-0.6 versions of libpcap,
|
|
and have this bug; WinPcap 2.3 is based on libpcap 0.6.2, and doesn't have
|
|
this bug.
|
|
|
|
If you are running Wireshark on a UNIX-flavored platform, run "wireshark
|
|
-v", or select "About Wireshark..." from the "Help" menu in Wireshark, to
|
|
see what version of libpcap it's using. If it's not 0.6 or later, you will
|
|
need either to upgrade your OS to get a later version of libpcap, or will
|
|
need to build and install a later version of libpcap from the tcpdump.org
|
|
Web site and then recompile Wireshark from source with that later version of
|
|
libpcap.
|
|
|
|
If you are running Wireshark on Windows with a pre-2.3 version of WinPcap,
|
|
you will need to un-install WinPcap and then download and install WinPcap
|
|
2.3.
|
|
|
|
Q 7.9: How can I capture packets with CRC errors?
|
|
|
|
A: Wireshark can capture only the packets that the packet capture library -
|
|
libpcap on UNIX-flavored OSes, and the WinPcap port to Windows of libpcap on
|
|
Windows - can capture, and libpcap/WinPcap can capture only the packets that
|
|
the OS's raw packet capture mechanism (or the WinPcap driver, and the
|
|
underlying OS networking code and network interface drivers, on Windows)
|
|
will allow it to capture.
|
|
|
|
Unless the OS always supplies packets with errors such as invalid CRCs to
|
|
the raw packet capture mechanism, or can be configured to do so, invalid
|
|
CRCs to the raw packet capture mechanism, Wireshark - and other programs
|
|
that capture raw packets, such as tcpdump - cannot capture those packets.
|
|
You will have to determine whether your OS needs to be so configured and, if
|
|
so, can be so configured, configure it if necessary and possible, and make
|
|
whatever changes to libpcap and the packet capture program you're using are
|
|
necessary, if any, to support capturing those packets.
|
|
|
|
Most OSes probably do not support capturing packets with invalid CRCs on
|
|
Ethernet, and probably do not support it on most other link-layer types.
|
|
Some drivers on some OSes do support it, such as some Ethernet drivers on
|
|
FreeBSD; in those OSes, you might always get those packets, or you might
|
|
only get them if you capture in promiscuous mode (you'd have to determine
|
|
which is the case).
|
|
|
|
Note that libpcap does not currently supply to programs that use it an
|
|
indication of whether the packet's CRC was invalid (because the drivers
|
|
themselves do not supply that information to the raw packet capture
|
|
mechanism); therefore, Wireshark will not indicate which packets had CRC
|
|
errors unless the FCS was captured (see the next question) and you're using
|
|
Wireshark 0.9.15 and later, in which case Wireshark will check the CRC and
|
|
indicate whether it's correct or not.
|
|
|
|
Q 7.10: How can I capture entire frames, including the FCS?
|
|
|
|
A: Wireshark can only capture data that the packet capture library - libpcap
|
|
on UNIX-flavored OSes, and the WinPcap port to Windows of libpcap on Windows
|
|
- can capture, and libpcap/WinPcap can capture only the data that the OS's
|
|
raw packet capture mechanism (or the WinPcap driver, and the underlying OS
|
|
networking code and network interface drivers, on Windows) will allow it to
|
|
capture.
|
|
|
|
For any particular link-layer network type, unless the OS supplies the FCS
|
|
of a frame as part of the frame, or can be configured to do so, Wireshark -
|
|
and other programs that capture raw packets, such as tcpdump - cannot
|
|
capture the FCS of a frame. You will have to determine whether your OS needs
|
|
to be so configured and, if so, can be so configured, configure it if
|
|
necessary and possible, and make whatever changes to libpcap and the packet
|
|
capture program you're using are necessary, if any, to support capturing the
|
|
FCS of a frame.
|
|
|
|
Most OSes do not support capturing the FCS of a frame on Ethernet, and
|
|
probably do not support it on most other link-layer types. Some drivres on
|
|
some OSes do support it, such as some (all?) Ethernet drivers on NetBSD and
|
|
possibly the driver for Apple's gigabit Ethernet interface in Mac OS X; in
|
|
those OSes, you might always get the FCS, or you might only get the FCS if
|
|
you capture in promiscuous mode (you'd have to determine which is the case).
|
|
|
|
Versions of Wireshark prior to 0.9.15 will not treat an Ethernet FCS in a
|
|
captured packet as an FCS. 0.9.15 and later will attempt to determine
|
|
whether there's an FCS at the end of the frame and, if it thinks there is,
|
|
will display it as such, and will check whether it's the correct CRC-32
|
|
value or not.
|
|
|
|
Q 7.11: I'm capturing packets on a machine on a VLAN; why don't the packets
|
|
I'm capturing have VLAN tags?
|
|
|
|
A: You might be capturing on what might be called a "VLAN interface" - the
|
|
way a particular OS makes VLANs plug into the networking stack might, for
|
|
example, be to have a network device object for the physical interface,
|
|
which takes VLAN packets, strips off the VLAN header and constructs an
|
|
Ethernet header, and passes that packet to an internal network device object
|
|
for the VLAN, which then passes the packets onto various higher-level
|
|
protocol implementations.
|
|
|
|
In order to see the raw Ethernet packets, rather than "de-VLANized" packets,
|
|
you would have to capture not on the virtual interface for the VLAN, but on
|
|
the interface corresponding to the physical network device, if possible. See
|
|
the Wireshark Wiki item on VLAN capturing for details.
|
|
|
|
Q 7.12: Why does Wireshark hang after I stop a capture?
|
|
|
|
A: The most likely reason for this is that Wireshark is trying to look up an
|
|
IP address in the capture to convert it to a name (so that, for example, it
|
|
can display the name in the source address or destination address columns),
|
|
and that lookup process is taking a very long time.
|
|
|
|
Wireshark calls a routine in the OS of the machine on which it's running to
|
|
convert of IP addresses to the corresponding names. That routine probably
|
|
does one or more of:
|
|
* a search of a system file listing IP addresses and names;
|
|
* a lookup using DNS;
|
|
* on UNIX systems, a lookup using NIS;
|
|
* on Windows systems, a NetBIOS-over-TCP query.
|
|
|
|
If a DNS server that's used in an address lookup is not responding, the
|
|
lookup will fail, but will only fail after a timeout while the system
|
|
routine waits for a reply.
|
|
|
|
In addition, on Windows systems, if the DNS lookup of the address fails,
|
|
either because the server isn't responding or because there are no records
|
|
in the DNS that could be used to map the address to a name, a
|
|
NetBIOS-over-TCP query will be made. That query involves sending a message
|
|
to the NetBIOS-over-TCP name service on that machine, asking for the name
|
|
and other information about the machine. If the machine isn't running
|
|
software that responds to those queries - for example, many non-Windows
|
|
machines wouldn't be running that software - the lookup will only fail after
|
|
a timeout. Those timeouts can cause the lookup to take a long time.
|
|
|
|
If you disable network address-to-name translation - for example, by turning
|
|
off the "Enable network name resolution" option in the "Capture Options"
|
|
dialog box for starting a network capture - the lookups of the address won't
|
|
be done, which may speed up the process of reading the capture file after
|
|
the capture is stopped. You can make that setting the default by selecting
|
|
"Preferences" from the "Edit" menu, turning off the "Enable network name
|
|
resolution" option in the "Name resolution" options in the preferences
|
|
disalog box, and using the "Save" button in that dialog box; note that this
|
|
will save all your current preference settings.
|
|
|
|
If Wireshark hangs when reading a capture even with network name resolution
|
|
turned off, there might, for example, be a bug in one of Wireshark's
|
|
dissectors for a protocol causing it to loop infinitely. If you're not
|
|
running the most recent release of Wireshark, you should first upgrade to
|
|
that release, as, if there's a bug of that sort, it might've been fixed in a
|
|
release after the one you're running. If the hang occurs in the most recent
|
|
release of Wireshark, the bug should be reported to the Wireshark
|
|
developers' mailing list at wireshark-dev@wireshark.org.
|
|
|
|
On UNIX-flavored OSes, please try to force Wireshark to dump core, by
|
|
sending it a SIGABRT signal (usually signal 6) with the kill command, and
|
|
then get a stack trace if you have a debugger installed. A stack trace can
|
|
be obtained by using your debugger (gdb in this example), the Wireshark
|
|
binary, and the resulting core file. Here's an example of how to use the gdb
|
|
command backtrace to do so.
|
|
$ gdb wireshark core
|
|
(gdb) backtrace
|
|
..... prints the stack trace
|
|
(gdb) quit
|
|
$
|
|
|
|
The core dump file may be named "wireshark.core" rather than "core" on some
|
|
platforms (e.g., BSD systems).
|
|
|
|
Also, if at all possible, please send a copy of the capture file that caused
|
|
the problem; when capturing packets, Wireshark normally writes captured
|
|
packets to a temporary file, which will probably be in /tmp or /var/tmp on
|
|
UNIX-flavored OSes, \TEMP on the main system disk (normally C:) on Windows
|
|
9x/Me/NT 4.0, and \Documents and Settings\your login name\Local
|
|
Settings\Temp on the main system disk on Windows 2000/Windows XP/Windows
|
|
Server 2003, so the capture file will probably be there. It will have a name
|
|
beginning with ether, with some mixture of letters and numbers after that.
|
|
Please don't send a trace file greater than 1 MB when compressed; instead,
|
|
make it available via FTP or HTTP, or say it's available but leave it up to
|
|
a developer to ask for it. If the trace file contains sensitive information
|
|
(e.g., passwords), then please do not send it.
|
|
|
|
8. Capturing packets on Windows
|
|
|
|
Q 8.1: I'm running Wireshark on Windows; why does some network interface on
|
|
my machine not show up in the list of interfaces in the "Interface:" field
|
|
in the dialog box popped up by "Capture->Start", and/or why does Wireshark
|
|
give me an error if I try to capture on that interface?
|
|
|
|
A: If you are running Wireshark on Windows NT 4.0, Windows 2000, Windows XP,
|
|
or Windows Server 2003, and this is the first time you have run a
|
|
WinPcap-based program (such as Wireshark, or TShark, or WinDump, or
|
|
Analyzer, or...) since the machine was rebooted, you need to run that
|
|
program from an account with administrator privileges; once you have run
|
|
such a program, you will not need administrator privileges to run any such
|
|
programs until you reboot.
|
|
|
|
If you are running on Windows 95/98/Me, or if you are running on Windows NT
|
|
4.0/Windows 2000/Windows XP/Windows Server 2003 and have administrator
|
|
privileges or a WinPcap-based program has been run with those privileges
|
|
since the machine rebooted, this problem might clear up if you completely
|
|
un-install WinPcap and then re-install it.
|
|
|
|
If that doesn't work, then note that Wireshark relies on the WinPcap
|
|
library, on the WinPcap device driver, and on the facilities that come with
|
|
the OS on which it's running in order to do captures.
|
|
|
|
Therefore, if the OS, the WinPcap library, or the WinPcap driver don't
|
|
support capturing on a particular network interface device, Wireshark won't
|
|
be able to capture on that device.
|
|
|
|
Note that:
|
|
1. 2.02 and earlier versions of the WinPcap driver and library that
|
|
Wireshark uses for packet capture didn't support Token Ring interfaces;
|
|
versions 2.1 and later support Token Ring, and the current version of
|
|
Wireshark works with (and, in fact, requires) WinPcap 2.1 or later.
|
|
If you are having problems capturing on Token Ring interfaces, and you
|
|
have WinPcap 2.02 or an earlier version of WinPcap installed, you should
|
|
uninstall WinPcap, download and install the current version of WinPcap,
|
|
and then install the latest version of Wireshark.
|
|
2. On Windows 95, 98, or Me, sometimes more than one interface will be
|
|
given the same name; if that is the case, you will only be able to
|
|
capture on one of those interfaces - it's not clear to which one the
|
|
name, when used in a WinPcap-based application, will refer. For example,
|
|
if you have a PPP serial interface and a VPN interface, they might show
|
|
up with the same name, for example "ppp-mac", and if you try to capture
|
|
on "ppp-mac", it might not capture on the interface you're currently
|
|
using. In that case, you might, for example, have to remove the VPN
|
|
interface from the system in order to capture on the PPP serial
|
|
interface.
|
|
3. WinPcap 2.3 has problems supporting PPP WAN interfaces on Windows NT
|
|
4.0, Windows 2000, Windows XP, and Windows Server 2003, and, to avoid
|
|
those problems, support for PPP WAN interfaces on those versions of
|
|
Windows has been disabled in WinPcap 3.0. Regular dial-up lines, ISDN
|
|
lines, ADSL connections using PPPoE or PPPoA, and various other lines
|
|
such as T1/E1 lines are all PPP interfaces, so those interfaces might
|
|
not show up on the list of interfaces in the "Capture Options" dialog on
|
|
those OSes.
|
|
On Windows 2000, Windows XP, and Windows Server 2003, but not Windows NT
|
|
4.0 or Windows Vista Beta 1, you should be able to capture on the
|
|
"GenericDialupAdapter" with WinPcap 3.1. (3.1 beta releases called it
|
|
the "NdisWanAdapter"; if you're using a 3.1 beta release, you should
|
|
un-install it and install the final 3.1 release.) See the Wireshark Wiki
|
|
item on PPP capturing for details.
|
|
4. WinPcap prior to 3.0 does not support multiprocessor machines (note that
|
|
machines with a single multi-threaded processor, such as Intel's new
|
|
multi-threaded x86 processors, are multiprocessor machines as far as the
|
|
OS and WinPcap are concerned), and recent 2.x versions of WinPcap refuse
|
|
to operate if they detect that they're running on a multiprocessor
|
|
machine, which means that they may not show any network interfaces. You
|
|
will need to use WinPcap 3.0 to capture on a multiprocessor machine.
|
|
|
|
If an interface doesn't show up in the list of interfaces in the
|
|
"Interface:" field, and you know the name of the interface, try entering
|
|
that name in the "Interface:" field and capturing on that device.
|
|
|
|
If the attempt to capture on it succeeds, the interface is somehow not being
|
|
reported by the mechanism Wireshark uses to get a list of interfaces. Try
|
|
listing the interfaces with WinDump; see the WinDump Web site for
|
|
information on using WinDump.
|
|
|
|
You would run WinDump with the -D flag; if it lists the interface, please
|
|
report this to wireshark-dev@wireshark.org giving full details of the
|
|
problem, including
|
|
* the operating system you're using, and the version of that operating
|
|
system;
|
|
* the type of network device you're using;
|
|
* the output of WinDump.
|
|
|
|
If WinDump does not list the interface, this is almost certainly a problem
|
|
with one or more of:
|
|
* the operating system you're using;
|
|
* the device driver for the interface you're using;
|
|
* the WinPcap library and/or the WinPcap device driver;
|
|
|
|
so first check the WinPcap FAQ or the Wiretapped.net mirror of that FAQ, to
|
|
see if your problem is mentioned there. If not, then see the WinPcap support
|
|
page - check the "Submitting bugs" section.
|
|
|
|
If you are having trouble capturing on a particular network interface, first
|
|
try capturing on that device with WinDump; see the WinDump Web site for
|
|
information on using WinDump.
|
|
|
|
If you can capture on the interface with WinDump, send mail to
|
|
wireshark-users@wireshark.org giving full details of the problem, including
|
|
* the operating system you're using, and the version of that operating
|
|
system;
|
|
* the type of network device you're using;
|
|
* the error message you get from Wireshark.
|
|
|
|
If you cannot capture on the interface with WinDump, this is almost
|
|
certainly a problem with one or more of:
|
|
* the operating system you're using;
|
|
* the device driver for the interface you're using;
|
|
* the WinPcap library and/or the WinPcap device driver;
|
|
|
|
so first check the WinPcap FAQ or the Wiretapped.net mirror of that FAQ, to
|
|
see if your problem is mentioned there. If not, then see the WinPcap support
|
|
page - check the "Submitting bugs" section.
|
|
|
|
You may also want to ask the wireshark-users@wireshark.org and the
|
|
winpcap-users@winpcap.org mailing lists to see if anybody happens to know
|
|
about the problem and know a workaround or fix for the problem. (Note that
|
|
you will have to subscribe to that list in order to be allowed to mail to
|
|
it; see the WinPcap support page for information on the mailing list.) In
|
|
your mail, please give full details of the problem, as described above, and
|
|
also indicate that the problem occurs with WinDump, not just with Wireshark.
|
|
|
|
Q 8.2: I'm running Wireshark on Windows; why do no network interfaces show
|
|
up in the list of interfaces in the "Interface:" field in the dialog box
|
|
popped up by "Capture->Start"?
|
|
|
|
A: This is really the same question as the previous one; see the response to
|
|
that question.
|
|
|
|
Q 8.3: I'm running Wireshark on Windows; why doesn't my serial port/ADSL
|
|
modem/ISDN modem show up in the list of interfaces in the "Interface:" field
|
|
in the dialog box popped up by "Capture->Start"?
|
|
|
|
A: Internet access on those devices is often done with the Point-to-Point
|
|
(PPP) protocol; WinPcap 2.3 has problems supporting PPP WAN interfaces on
|
|
Windows NT 4.0, Windows 2000, Windows XP, and Windows Server 2003, and, to
|
|
avoid those problems, support for PPP WAN interfaces on those versions of
|
|
Windows has been disabled in WinPcap 3.0.
|
|
|
|
On Windows 2000, Windows XP, and Windows Server 2003, but not Windows NT 4.0
|
|
or Windows Vista Beta 1, you should be able to capture on the
|
|
"GenericDialupAdapter" with WinPcap 3.1. (3.1 beta releases called it the
|
|
"NdisWanAdapter"; if you're using a 3.1 beta release, you should un-install
|
|
it and install the final 3.1 release.) See the Wireshark Wiki item on PPP
|
|
capturing for details.
|
|
|
|
Q 8.4: I'm running Wireshark on Windows NT 4.0/Windows 2000/Windows
|
|
XP/Windows Server 2003; my machine has a PPP (dial-up POTS, ISDN, etc.)
|
|
interface, and it shows up in the "Interface" item in the "Capture Options"
|
|
dialog box. Why can no packets be sent on or received from that network
|
|
while I'm trying to capture traffic on that interface?
|
|
|
|
A: Some versions of WinPcap have problems with PPP WAN interfaces on Windows
|
|
NT 4.0, Windows 2000, Windows XP, and Windows Server 2003; one symptom that
|
|
may be seen is that attempts to capture in promiscuous mode on the interface
|
|
cause the interface to be incapable of sending or receiving packets. You can
|
|
disable promiscuous mode using the -p command-line flag or the item in the
|
|
"Capture Preferences" dialog box, but this may mean that outgoing packets,
|
|
or incoming packets, won't be seen in the capture.
|
|
|
|
On Windows 2000, Windows XP, and Windows Server 2003, but not Windows NT 4.0
|
|
or Windows Vista Beta 1, you should be able to capture on the
|
|
"GenericDialupAdapter" with WinPcap 3.1. (3.1 beta releases called it the
|
|
"NdisWanAdapter"; if you're using a 3.1 beta release, you should un-install
|
|
it and install the final 3.1 release.) See the Wireshark Wiki item on PPP
|
|
capturing for details.
|
|
|
|
Q 8.5: I'm running Wireshark on Windows 95/98/Me, on a machine with more
|
|
than one network adapter of the same type; why does Wireshark show all of
|
|
those adapters with the same name, not letting me use any of those adapters
|
|
other than the first one?
|
|
|
|
A: Unfortunately, Windows 95/98/Me gives the same name to multiple instances
|
|
of the type of same network adapter. Therefore, WinPcap cannot distinguish
|
|
between them, so a WinPcap-based application can capture only on the first
|
|
such interface; Wireshark is a libpcap/WinPcap-based application.
|
|
|
|
Q 8.6: I'm running Wireshark on Windows; why am I not seeing any traffic
|
|
being sent by the machine running Wireshark?
|
|
|
|
A: If you are running some form of VPN client software, it might be causing
|
|
this problem; people have seen this problem when they have Check Point's VPN
|
|
software installed on their machine. If that's the cause of the problem, you
|
|
will have to remove the VPN software in order to have Wireshark (or any
|
|
other application using WinPcap) see outgoing packets; unfortunately,
|
|
neither we nor the WinPcap developers know any way to make WinPcap and the
|
|
VPN software work well together.
|
|
|
|
Also, some drivers for Windows (especially some wireless network interface
|
|
drivers) apparently do not, when running in promiscuous mode, arrange that
|
|
outgoing packets are delivered to the software that requested that the
|
|
interface run promiscuously; try turning promiscuous mode off.
|
|
|
|
Q 8.7: When I capture on Windows in promiscuous mode, I can see packets
|
|
other than those sent to or from my machine; however, those packets show up
|
|
with a "Short Frame" indication, unlike packets to or from my machine. What
|
|
should I do to arrange that I see those packets in their entirety?
|
|
|
|
A: In at least some cases, this appears to be the result of PGPnet running
|
|
on the network interface on which you're capturing; turn it off on that
|
|
interface.
|
|
|
|
Q 8.8: I'm capturing packets on {Windows 95, Windows 98, Windows Me}; why
|
|
are the time stamps on packets wrong?
|
|
|
|
A: This is due to a bug in WinPcap. The bug should be fixed in WinPcap 3.0
|
|
and later releases.
|
|
|
|
Q 8.9: I'm trying to capture 802.11 traffic on Windows; why am I not seeing
|
|
any packets?
|
|
|
|
A: At least some 802.11 card drivers on Windows appear not to see any
|
|
packets if they're running in promiscuous mode. Try turning promiscuous mode
|
|
off; you'll only be able to see packets sent by and received by your
|
|
machine, not third-party traffic, and it'll look like Ethernet traffic and
|
|
won't include any management or control frames, but that's a limitation of
|
|
the card drivers.
|
|
|
|
See MicroLogix's list of cards supported with WinPcap for information on
|
|
support of various adapters and drivers with WinPcap.
|
|
|
|
Q 8.10: I'm trying to capture 802.11 traffic on Windows; why am I seeing
|
|
packets received by the machine on which I'm capturing traffic, but not
|
|
packets sent by that machine?
|
|
|
|
A: This appears to be another problem with promiscuous mode; try turning it
|
|
off.
|
|
|
|
Q 8.11: I'm trying to capture Ethernet VLAN traffic on Windows, and I'm
|
|
capturing on a "raw" Ethernet device rather than a "VLAN interface", so that
|
|
I can see the VLAN headers; why am I seeing packets received by the machine
|
|
on which I'm capturing traffic, but not packets sent by that machine?
|
|
|
|
A: The way the Windows networking code works probably means that packets are
|
|
sent on a "VLAN interface" rather than the "raw" device, so packets sent by
|
|
the machine will only be seen when you capture on the "VLAN interface". If
|
|
so, you will be unable to see outgoing packets when capturing on the "raw"
|
|
device, so you are stuck with a choice between seeing VLAN headers and
|
|
seeing outgoing packets.
|
|
|
|
9. Capturing packets on UN*Xes
|
|
|
|
Q 9.1: I'm running Wireshark on a UNIX-flavored OS; why does some network
|
|
interface on my machine not show up in the list of interfaces in the
|
|
"Interface:" field in the dialog box popped up by "Capture->Start", and/or
|
|
why does Wireshark give me an error if I try to capture on that interface?
|
|
|
|
A: You may need to run Wireshark from an account with sufficient privileges
|
|
to capture packets, such as the super-user account, or may need to give your
|
|
account sufficient privileges to capture packets. Only those interfaces that
|
|
Wireshark can open for capturing show up in that list; if you don't have
|
|
sufficient privileges to capture on any interfaces, no interfaces will show
|
|
up in the list. See the Wireshark Wiki item on capture privileges for
|
|
details on how to give a particular account or account group capture
|
|
privileges on platforms where that can be done.
|
|
|
|
If you are running Wireshark from an account with sufficient privileges,
|
|
then note that Wireshark relies on the libpcap library, and on the
|
|
facilities that come with the OS on which it's running in order to do
|
|
captures. On some OSes, those facilities aren't present by default; see the
|
|
Wireshark Wiki item on adding capture support for details.
|
|
|
|
And, even if you're running with an account that has sufficient privileges
|
|
to capture, and capture support is present in your OS, if the OS or the
|
|
libpcap library don't support capturing on a particular network interface
|
|
device or particular types of devices, Wireshark won't be able to capture on
|
|
that device.
|
|
|
|
On Solaris, note that libpcap 0.6.2 and earlier didn't support Token Ring
|
|
interfaces; the current version, 0.7.2, does support Token Ring, and the
|
|
current version of Wireshark works with libcap 0.7.2 and later.
|
|
|
|
If an interface doesn't show up in the list of interfaces in the
|
|
"Interface:" field, and you know the name of the interface, try entering
|
|
that name in the "Interface:" field and capturing on that device.
|
|
|
|
If the attempt to capture on it succeeds, the interface is somehow not being
|
|
reported by the mechanism Wireshark uses to get a list of interfaces; please
|
|
report this to wireshark-dev@wireshark.org giving full details of the
|
|
problem, including
|
|
* the operating system you're using, and the version of that operating
|
|
system (for Linux, give both the version number of the kernel and the
|
|
name and version number of the distribution you're using);
|
|
* the type of network device you're using.
|
|
|
|
If you are having trouble capturing on a particular network interface, and
|
|
you've made sure that (on platforms that require it) you've arranged that
|
|
packet capture support is present, as per the above, first try capturing on
|
|
that device with tcpdump.
|
|
|
|
If you can capture on the interface with tcpdump, send mail to
|
|
wireshark-users@wireshark.org giving full details of the problem, including
|
|
* the operating system you're using, and the version of that operating
|
|
system (for Linux, give both the version number of the kernel and the
|
|
name and version number of the distribution you're using);
|
|
* the type of network device you're using;
|
|
* the error message you get from Wireshark.
|
|
|
|
If you cannot capture on the interface with tcpdump, this is almost
|
|
certainly a problem with one or more of:
|
|
* the operating system you're using;
|
|
* the device driver for the interface you're using;
|
|
* the libpcap library;
|
|
|
|
so you should report the problem to the company or organization that
|
|
produces the OS (in the case of a Linux distribution, report the problem to
|
|
whoever produces the distribution).
|
|
|
|
You may also want to ask the wireshark-users@wireshark.org and the
|
|
tcpdump-workers@tcpdump.org mailing lists to see if anybody happens to know
|
|
about the problem and know a workaround or fix for the problem. In your
|
|
mail, please give full details of the problem, as described above, and also
|
|
indicate that the problem occurs with tcpdump not just with Wireshark.
|
|
|
|
Q 9.2: I'm running Wireshark on a UNIX-flavored OS; why do no network
|
|
interfaces show up in the list of interfaces in the "Interface:" field in
|
|
the dialog box popped up by "Capture->Start"?
|
|
|
|
A: This is really the same question as the previous one; see the response to
|
|
that question.
|
|
|
|
Q 9.3: I'm capturing packets on Linux; why do the time stamps have only
|
|
100ms resolution, rather than 1us resolution?
|
|
|
|
A: Wireshark gets time stamps from libpcap/WinPcap, and libpcap/WinPcap get
|
|
them from the OS kernel, so Wireshark - and any other program using libpcap,
|
|
such as tcpdump - is at the mercy of the time stamping code in the OS for
|
|
time stamps.
|
|
|
|
At least on x86-based machines, Linux can get high-resolution time stamps on
|
|
newer processors with the Time Stamp Counter (TSC) register; for example,
|
|
Intel x86 processors, starting with the Pentium Pro, and including all x86
|
|
processors since then, have had a TSC, and other vendors probably added the
|
|
TSC at some point to their families of x86 processors.
|
|
|
|
The Linux kernel must be configured with the CONFIG_X86_TSC option enabled
|
|
in order to use the TSC. Make sure this option is enabled in your kernel.
|
|
|
|
In addition, some Linux distributions may have bugs in their versions of the
|
|
kernel that cause packets not to be given high-resolution time stamps even
|
|
if the TSC is enabled. See, for example, bug 61111 for Red Hat Linux 7.2. If
|
|
your distribution has a bug such as this, you may have to run a standard
|
|
kernel from kernel.org in order to get high-resolution time stamps.
|
|
|
|
10. Capturing packets on wireless LANs
|
|
|
|
Q 10.1: How can I capture raw 802.11 frames, including non-data (management,
|
|
beacon) frames?
|
|
|
|
A: That depends on the operating system on which you're running, and on the
|
|
802.11 interface on which you're capturing.
|
|
|
|
This would probably require that you capture in promiscuous mode or in the
|
|
mode called "monitor mode" or "RFMON mode". On some platforms, or with some
|
|
cards, this might require that you capture in monitor mode - promiscuous
|
|
mode might not be sufficient. If you want to capture traffic on networks
|
|
other than the one with which you're associated, you will have to capture in
|
|
monitor mode.
|
|
|
|
Not all operating systems support capturing non-data packets and, even on
|
|
operating systems that do support it, not all drivers, and thus not all
|
|
interfaces, support it. Even on those that do, monitor mode might not be
|
|
supported by the operating system or by the drivers for all interfaces.
|
|
|
|
NOTE: an interface running in monitor mode will, on most if not all
|
|
platforms, not be able to act as a regular network interface; putting it
|
|
into monitor mode will, in effect, take your machine off of whatever network
|
|
it's on as long as the interface is in monitor mode, allowing it only to
|
|
passively capture packets.
|
|
|
|
This means that you should disable name resolution when capturing in monitor
|
|
mode; otherwise, when Wireshark (or TShark, or tcpdump) tries to display IP
|
|
addresses as host names, it will probably block for a long time trying to
|
|
resolve the name because it will not be able to communicate with any DNS or
|
|
NIS servers.
|
|
|
|
See the Wireshark Wiki item on 802.11 capturing for details.
|
|
|
|
Q 10.2: How do I capture on an 802.11 device in monitor mode?
|
|
|
|
A: Whether you will be able to capture in monitor mode depends on the
|
|
operating system, adapter, and driver you're using. See the previous
|
|
question for information on monitor mode, including a link to the Wireshark
|
|
Wiki page that gives details on 802.11 capturing.
|
|
|
|
11. Viewing traffic
|
|
|
|
Q 11.1: Why am I seeing lots of packets with incorrect TCP checksums?
|
|
|
|
A: If the packets that have incorrect TCP checksums are all being sent by
|
|
the machine on which Wireshark is running, this is probably because the
|
|
network interface on which you're capturing does TCP checksum offloading.
|
|
That means that the TCP checksum is added to the packet by the network
|
|
interface, not by the OS's TCP/IP stack; when capturing on an interface,
|
|
packets being sent by the host on which you're capturing are directly handed
|
|
to the capture interface by the OS, which means that they are handed to the
|
|
capture interface without a TCP checksum being added to them.
|
|
|
|
The only way to prevent this from happening would be to disable TCP checksum
|
|
offloading, but
|
|
1. that might not even be possible on some OSes;
|
|
2. that could reduce networking performance significantly.
|
|
|
|
However, you can disable the check that Wireshark does of the TCP checksum,
|
|
so that it won't report any packets as having TCP checksum errors, and so
|
|
that it won't refuse to do TCP reassembly due to a packet having an
|
|
incorrect TCP checksum. That can be set as an Wireshark preference by
|
|
selecting "Preferences" from the "Edit" menu, opening up the "Protocols"
|
|
list in the left-hand pane of the "Preferences" dialog box, selecting "TCP",
|
|
from that list, turning off the "Check the validity of the TCP checksum when
|
|
possible" option, clicking "Save" if you want to save that setting in your
|
|
preference file, and clicking "OK".
|
|
|
|
It can also be set on the Wireshark or TShark command line with a -o
|
|
tcp.check_checksum:false command-line flag, or manually set in your
|
|
preferences file by adding a tcp.check_checksum:false line.
|
|
|
|
Q 11.2: I've just installed Wireshark, and the traffic on my local LAN is
|
|
boring. Where can I find more interesting captures?
|
|
|
|
A: We have a collection of strange and exotic sample capture files at
|
|
http://wiki.wireshark.org/SampleCaptures
|
|
|
|
Q 11.3: Why doesn't Wireshark correctly identify RTP packets? It shows them
|
|
only as UDP.
|
|
|
|
A: Wireshark can identify a UDP datagram as containing a packet of a
|
|
particular protocol running atop UDP only if
|
|
1. The protocol in question has a particular standard port number, and the
|
|
UDP source or destination port number is that port
|
|
2. Packets of that protocol can be identified by looking for a "signature"
|
|
of some type in the packet - i.e., some data that, if Wireshark finds it
|
|
in some particular part of a packet, means that the packet is almost
|
|
certainly a packet of that type.
|
|
3. Some other traffic earlier in the capture indicated that, for example,
|
|
UDP traffic between two particular addresses and ports will be RTP
|
|
traffic.
|
|
|
|
RTP doesn't have a standard port number, so 1) doesn't work; it doesn't, as
|
|
far as I know, have any "signature", so 2) doesn't work.
|
|
|
|
That leaves 3). If there's RTSP traffic that sets up an RTP session, then,
|
|
at least in some cases, the RTSP dissector will set things up so that
|
|
subsequent RTP traffic will be identified. Currently, that's the only place
|
|
we do that; there may be other places.
|
|
|
|
However, there will always be places where Wireshark is simply incapable of
|
|
deducing that a given UDP flow is RTP; a mechanism would be needed to allow
|
|
the user to specify that a given conversation should be treated as RTP. As
|
|
of Wireshark 0.8.16, such a mechanism exists; if you select a UDP or TCP
|
|
packet, the right mouse button menu will have a "Decode As..." menu item,
|
|
which will pop up a dialog box letting you specify that the source port, the
|
|
destination port, or both the source and destination ports of the packet
|
|
should be dissected as some particular protocol.
|
|
|
|
Q 11.4: Why doesn't Wireshark show Yahoo Messenger packets in captures that
|
|
contain Yahoo Messenger traffic?
|
|
|
|
A: Wireshark only recognizes as Yahoo Messenger traffic packets to or from
|
|
TCP port 3050 that begin with "YPNS", "YHOO", or "YMSG". TCP segments that
|
|
start with the middle of a Yahoo Messenger packet that takes more than one
|
|
TCP segment will not be recognized as Yahoo Messenger packets (even if the
|
|
TCP segment also contains the beginning of another Yahoo Messenger packet).
|
|
|
|
12. Filtering traffic
|
|
|
|
Q 12.1: I saved a filter and tried to use its name to filter the display;
|
|
why do I get an "Unexpected end of filter string" error?
|
|
|
|
A: You cannot use the name of a saved display filter as a filter. To filter
|
|
the display, you can enter a display filter expression - not the name of a
|
|
saved display filter - in the "Filter:" box at the bottom of the display,
|
|
and type the key or press the "Apply" button (that does not require you to
|
|
have a saved filter), or, if you want to use a saved filter, you can press
|
|
the "Filter:" button, select the filter in the dialog box that pops up, and
|
|
press the "OK" button.
|
|
|
|
Q 12.2: How can I search for, or filter, packets that have a particular
|
|
string anywhere in them?
|
|
|
|
A: If you want to do this when capturing, you can't. That's a feature that
|
|
would be hard to implement in capture filters without changes to the capture
|
|
filter code, which, on many platforms, is in the OS kernel and, on other
|
|
platforms, is in the libpcap library.
|
|
|
|
In releases prior to 0.9.14, you also can't search for, or filter, packets
|
|
containing a particular string even after you've captured them.
|
|
|
|
In 0.9.14, you can search for, but not filter, packets that have a
|
|
particular string; this has been added to the "Find Frame" dialog ("Find
|
|
Frame" under the "Edit" menu, or control-F).
|
|
|
|
In 0.9.15 and later, you can search for those packets using either the
|
|
mechanism introduced in 0.9.14 or using the new "contains" operator in
|
|
filter expressions, which lets you search the entire packet or text string
|
|
or byte string fields in the packet; the "contains" operator can also be
|
|
used in expressions used to filter the display.
|
|
|
|
Q 12.3: How do I filter a capture to see traffic for virus XXX?
|
|
|
|
A: For some viruses/worms there might be a capture filter to recognize the
|
|
virus traffic. Check the CaptureFilters page on the Wireshark Wiki to see if
|
|
anybody's added such a filter.
|
|
|
|
Note that Wireshark was not designed to be an intrusion detection system;
|
|
you might be able to use it as an IDS, but in most cases software designed
|
|
to be an IDS, such as Snort or Prelude, will probably work better.
|
|
|
|
The Bleeding Edge of Snort has a collection of signatures for Snort to
|
|
detect various viruses, worms, and the like.
|