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Diffstat (limited to 'help')
| -rw-r--r-- | help/faq.txt | 384 |
1 files changed, 119 insertions, 265 deletions
diff --git a/help/faq.txt b/help/faq.txt index c23d5a8a1b..e2d657e3e4 100644 --- a/help/faq.txt +++ b/help/faq.txt @@ -9,8 +9,8 @@ INDEX -1. General Questions: - + 1. General Questions: + 1.1 What is Wireshark? 1.2 What's up with the name change? Is Wireshark a fork? @@ -36,21 +36,19 @@ 1.12 What devices can Wireshark use to capture packets? - 1.13 Does Wireshark work on Windows Me? - - 1.14 Does Wireshark work on Windows XP? - -2. Downloading Wireshark: - + 1.13 Does Wireshark work on Windows Vista? + + 2. Downloading Wireshark: + 2.1 Why do I get an error when I try to run the Win32 installer? - -3. Installing Wireshark: - + + 3. Installing Wireshark: + 3.1 I installed the Wireshark RPM (or other package); why did it install TShark but not Wireshark? - -4. Building Wireshark: - + + 4. Building Wireshark: + 4.1 I have libpcap installed; why did the configure script not find pcap.h or bpf.h? @@ -69,9 +67,9 @@ 4.5 When I try to build Wireshark on Windows, why does the build fail because of conflicts between winsock.h and winsock2.h? - -5. Starting Wireshark: - + + 5. Starting Wireshark: + 5.1 Why does Wireshark crash with a Bus Error when I try to run it on Solaris 8? @@ -82,22 +80,19 @@ 5.3 When I try to run Wireshark, why does it complain about sprint_realloc_objid being undefined? - 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? - - 5.5 I've installed Wireshark from Fink on Mac OS X; why is it very slow + 5.4 I've installed Wireshark from Fink on Mac OS X; why is it very slow to start up? - -6. Crashes and other fatal errors: - + + 6. Crashes and other fatal errors: + 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? 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? - -7. Capturing packets: - + + 7. Capturing packets: + 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? @@ -128,9 +123,9 @@ packets I'm capturing have VLAN tags? 7.12 Why does Wireshark hang after I stop a capture? - -8. Capturing packets on Windows: - + + 8. Capturing packets on Windows: + 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 @@ -150,38 +145,30 @@ 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? - 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? - - 8.6 I'm running Wireshark on Windows; why am I not seeing any traffic + 8.5 I'm running Wireshark on Windows; why am I not seeing any traffic being sent by the machine running Wireshark? - 8.7 When I capture on Windows in promiscuous mode, I can see packets + 8.6 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? - 8.8 I'm capturing packets on {Windows 95, Windows 98, Windows Me}; why - are the time stamps on packets wrong? - - 8.9 I'm trying to capture 802.11 traffic on Windows; why am I not + 8.7 I'm trying to capture 802.11 traffic on Windows; why am I not seeing any packets? - 8.10 I'm trying to capture 802.11 traffic on Windows; why am I seeing + 8.8 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? - 8.11 I'm trying to capture Ethernet VLAN traffic on Windows, and I'm + 8.9 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? - -9. Capturing packets on UN*Xes: - + + 9. Capturing packets on UN*Xes: + 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", @@ -194,16 +181,16 @@ 9.3 I'm capturing packets on Linux; why do the time stamps have only 100ms resolution, rather than 1us resolution? - -10. Capturing packets on wireless LANs: - + + 10. Capturing packets on wireless LANs: + 10.1 How can I capture raw 802.11 frames, including non-data (management, beacon) frames? 10.2 How do I capture on an 802.11 device in monitor mode? - -11. Viewing traffic: - + + 11. Viewing traffic: + 11.1 Why am I seeing lots of packets with incorrect TCP checksums? 11.2 I've just installed Wireshark, and the traffic on my local LAN is @@ -214,9 +201,9 @@ 11.4 Why doesn't Wireshark show Yahoo Messenger packets in captures that contain Yahoo Messenger traffic? - -12. Filtering traffic: - + + 12. Filtering traffic: + 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? @@ -225,47 +212,43 @@ 12.3 How do I filter a capture to see traffic for virus XXX? -1. General Questions + 1. General Questions Q 1.1: What is Wireshark? - A: Wireshark is the world's most popular network protocol analyzer. It + A: Wireshark® is the world's most popular network protocol analyzer. It has a rich and powerful feature set and runs on most computing - platforms including Windows, OS X, and Linux. Network professionals, - security experts, developers, and educators around the world use it - regularly. It is freely available as open source, and is released under - the GNU General Public License. - + platforms including Windows, OS X, Linux, and UNIX. Network + professionals, security experts, developers, and educators around the + world use it regularly. It is freely available as open source, and is + released under the GNU General Public License. It is developed and maintained by a global team of protocol experts, - and it is an example of a disruptive technology. Wireshark used to be - known as Ethereal®. See the next question for details about the name - change. If you're still using Ethereal, it is strongly recommended that - you upgrade to Wireshark. - + and it is an example of a disruptive technology. + Wireshark used to be known as Ethereal®. See the next question for + details about the name change. If you're still using Ethereal, it is + strongly recommended that you upgrade to Wireshark. For more information, please see the About Wireshark page. Q 1.2: What's up with the name change? Is Wireshark a fork? - A: In May of 2006, Gerald Combs (the original author of Ethereal®) went + A: In May of 2006, Gerald Combs (the original author of Ethereal) went to work for CACE Technologies (best known for WinPcap). Unfortunately, - he had to leave the Ethereal® trademarks behind. - + he had to leave the Ethereal trademarks behind. This left the project in an awkward position. The only reasonable way to ensure the continued success of the project was to change the name. This is how Wireshark was born. - Wireshark is almost (but not quite) a fork. Normally a "fork" of an open source project results in two names, web sites, development teams, support infrastructures, etc. This is the case with Wireshark except for one notable exception -- every member of the core development team - is now working on Wireshark. As far as anyone knows, there has been no - active development on Ethereal since the name change. Several parts of - the Ethereal web site (such as the mailing lists, source code - repository, and build farm) have gone offline. - + is now working on Wireshark. There has been no active development on + Ethereal since the name change. Several parts of the Ethereal web site + (such as the mailing lists, source code repository, and build farm) + have gone offline. More information on the name change can be found here: * * + * Many other articles in Q 1.3: Where can I get help? @@ -274,10 +257,8 @@ lists can be found at http://www.wireshark.org/mailman/listinfo. An IRC channel dedicated to Wireshark can be found at irc://irc.freenode.net/wireshark. - Self-paced and instructor-led training is available at Wireshark - University. A certification program will be announced in Q2 2007. - + University. A certification program will be announced in Q3 2007. Commercial support and development services are available from CACE Technologies. @@ -290,7 +271,6 @@ A: Wireshark is pronounced as the word wire followed immediately by the word shark. Exact pronunciation and emphasis may vary depending on your locale (e.g. Arkansas). - It's spelled with a capital W, followed by a lower-case ireshark. It is not a CamelCase word, i.e., WireShark is incorrect. @@ -300,7 +280,6 @@ license fee. The version of Wireshark you download isn't a "demo" version, with limitations not present in a "full" version; it is the full version. - The license under which Wireshark is issued is the GNU General Public License. See the GNU GPL FAQ for some more information. @@ -309,7 +288,6 @@ A: Yes, if, for example, you mean "I work for a commercial organization; can I use Wireshark to capture and analyze network traffic in our company's networks or in our customer's networks?" - If you mean "Can I use Wireshark as part of my commercial product?", see the next entry in the FAQ. @@ -326,7 +304,6 @@ more details; in particular, note the answer to the question about modifying a GPLed program and selling it commercially, and the question about linking GPLed code with other code to make a proprietary program. - You can combine a GPLed program such as Wireshark and a commercial program as long as they communicate "at arm's length", as per this item in the GPL FAQ. @@ -348,12 +325,10 @@ A: Support for particular protocols is added to Wireshark as a result of people contributing that support; no formal plans for adding support for particular protocols in particular future releases exist. - If a network analyzer writes out files in a format already supported by Wireshark (e.g., in libpcap format), Wireshark may already be able to read them, unless the analyzer has added its own proprietary extensions to that format. - If a network analyzer writes out files in its own format, or has added proprietary extensions to another format, in order to make Wireshark read captures from that network analyzer, we would either have to have @@ -363,7 +338,6 @@ detailed textual analysis of the packets in that capture file (showing packet time stamps, packet lengths, and the top-level packet header) in order to reverse-engineer the file format. - Note that there is no guarantee that we will be able to reverse-engineer a capture file format. @@ -375,7 +349,12 @@ Wireshark to do so), ATM connections (if the OS on which it's running allows Wireshark to do so), and the "any" device supported on Linux by recent versions of libpcap. - + See the list of supported capture media on various OSes for details + (several items in there say "Unknown", which doesn't mean "Wireshark + can't capture on them", it means "we don't know whether it can capture + on them"; we expect that it will be able to capture on many of them, + but we haven't tried it ourselves - if you try one of those types and + it works, please update the wiki page accordingly. It can also read a variety of capture file formats, including: * AG Group/WildPackets EtherPeek/TokenPeek/AiroPeek/EtherHelp/Packet Grabber captures @@ -410,30 +389,25 @@ other applications or equipment, even if it cannot itself capture on those network types. - Q 1.13: Does Wireshark work on Windows Me? - - A: Yes, but if you want to capture packets, you will need to install - the latest version of WinPcap, as 2.02 and earlier versions of WinPcap - didn't support Windows Me. You should also install the latest version - of Wireshark as well. + Q 1.13: Does Wireshark work on Windows Vista? - Q 1.14: Does Wireshark work on Windows XP? + A: Yes, but if you want to capture packets, you must make sure npf.sys + is loaded. You can do this by selecting Start WinPcap service "NPF" at + startup in the installer or by running sc config npf start= auto as + Administrator from the command line. You can also run Wireshark as + Administrator, but this is discouraged. See the CaputrePrivileges page + on the wiki for more details. - A: Yes, but if you want to capture packets, you will need to install - the latest version of WinPcap, as 2.2 and earlier versions of WinPcap - didn't support Windows XP. - -2. Downloading Wireshark + 2. Downloading Wireshark Q 2.1: Why do I get an error when I try to run the Win32 installer? A: The program you used to download it may have downloaded it - incorrectly. Web browsers sometimes may do this. - + incorrectly. Web browsers and download accelerators sometimes may do + this. Try downloading it with, for example: - * Wget, for which Windows binaries are available on the SunSITE FTP - server at sunsite.tk or Heiko Herold's windows wget spot - wGetGUI - offers a GUI interface that uses wget; + * Wget, for which Windows binaries are available from Christopher + Lewis or wGetGUI, which offers a GUI interface that uses wget; * WS_FTP from Ipswitch, * the ftp command that comes with Windows. @@ -441,7 +415,7 @@ mode rather than ASCII mode, by using the binary command before transferring the file. -3. Installing Wireshark + 3. Installing Wireshark Q 3.1: I installed the Wireshark RPM (or other package); why did it install TShark but not Wireshark? @@ -451,7 +425,7 @@ If this is the case on your system, there's probably a separate package named wireshark-gnome or wireshark-gtk+. Find it and install it. -4. Building Wireshark + 4. Building Wireshark Q 4.1: I have libpcap installed; why did the configure script not find pcap.h or bpf.h? @@ -461,7 +435,6 @@ "make install" is run. To install pcap.h and bpf.h, you must run "make install-incl". If you're running Debian or Redhat, make sure you have the "libpcap-dev" or "libpcap-devel" packages installed. - It's also possible that pcap.h and bpf.h have been installed in a strange location. If this is the case, you may have to tweak aclocal.m4. @@ -485,7 +458,6 @@ handling very long lines. On Solaris, for example, /usr/bin/sed has a line length limit too low to allow libtool to work; /usr/xpg4/bin/sed can handle it, as can GNU sed if you have it installed. - On Solaris, changing your command search path to search /usr/xpg4/bin before /usr/bin should make the problem go away; on any platform on which you have this problem, installing GNU sed and changing your @@ -519,11 +491,10 @@ (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 + 5. Starting Wireshark Q 5.1: Why does Wireshark crash with a Bus Error when I try to run it on Solaris 8? @@ -538,7 +509,6 @@ 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. @@ -560,37 +530,22 @@ 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 + Q 5.4: 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 + 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 + 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? @@ -619,7 +574,7 @@ or, for Windows, WinPcap bug that causes the system to crash when this happens; see the previous question. -7. Capturing packets + 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 @@ -629,10 +584,8 @@ 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 @@ -640,7 +593,6 @@ 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 @@ -649,7 +601,6 @@ 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 @@ -660,7 +611,6 @@ 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 @@ -681,23 +631,19 @@ 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 @@ -720,13 +666,11 @@ 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. @@ -736,7 +680,6 @@ 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. @@ -747,12 +690,10 @@ 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. @@ -763,7 +704,6 @@ 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 @@ -772,13 +712,13 @@ 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. + 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) @@ -802,17 +742,14 @@ 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. @@ -822,20 +759,16 @@ 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 @@ -843,7 +776,6 @@ 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. @@ -856,7 +788,6 @@ 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 @@ -866,14 +797,12 @@ 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 @@ -890,7 +819,6 @@ 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 @@ -899,7 +827,6 @@ 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 @@ -907,7 +834,6 @@ 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 @@ -924,7 +850,6 @@ 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 @@ -937,7 +862,6 @@ 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: @@ -949,7 +873,6 @@ 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, @@ -960,7 +883,6 @@ 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 @@ -971,7 +893,6 @@ 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 @@ -981,7 +902,6 @@ 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 @@ -996,7 +916,6 @@ 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 @@ -1011,7 +930,7 @@ for it. If the trace file contains sensitive information (e.g., passwords), then please do not send it. -8. Capturing packets on Windows + 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 @@ -1026,21 +945,17 @@ 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 you are running on Windows 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 @@ -1052,17 +967,7 @@ 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 + 2. 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 @@ -1076,7 +981,7 @@ 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 + 3. 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 @@ -1089,12 +994,10 @@ "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 @@ -1112,11 +1015,9 @@ 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 @@ -1134,7 +1035,6 @@ 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. @@ -1148,8 +1048,8 @@ 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. + A: This is really the same question as a 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 @@ -1161,7 +1061,6 @@ 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 @@ -1183,7 +1082,6 @@ 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 @@ -1191,18 +1089,7 @@ 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 + Q 8.5: 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 @@ -1212,14 +1099,13 @@ 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 + Q 8.6: 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 @@ -1229,13 +1115,7 @@ 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 + Q 8.7: 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 @@ -1244,18 +1124,17 @@ 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? + Q 8.8: 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 + Q 8.9: 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 @@ -1268,7 +1147,7 @@ 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 + 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 @@ -1285,29 +1164,24 @@ 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 @@ -1322,7 +1196,6 @@ 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 @@ -1342,7 +1215,6 @@ 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 @@ -1364,18 +1236,14 @@ 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. - + 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 @@ -1383,39 +1251,34 @@ have to run a standard kernel from kernel.org in order to get high-resolution time stamps. -10. Capturing packets on wireless LANs + 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? @@ -1425,7 +1288,7 @@ question for information on monitor mode, including a link to the Wireshark Wiki page that gives details on 802.11 capturing. -11. Viewing traffic + 11. Viewing traffic Q 11.1: Why am I seeing lots of packets with incorrect TCP checksums? @@ -1438,7 +1301,6 @@ 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; @@ -1454,7 +1316,6 @@ 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. @@ -1482,12 +1343,10 @@ 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 @@ -1508,7 +1367,7 @@ Messenger packets (even if the TCP segment also contains the beginning of another Yahoo Messenger packet). -12. Filtering traffic + 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? @@ -1528,14 +1387,11 @@ 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 @@ -1547,11 +1403,9 @@ 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. |