Ethereal is a network packet analyzer. A network packet analyzer will try to capture network packets and tries to display that packet data as detailed as possible. You could think of a network packet analyzer as a measuring device used to examine what's going on inside a network cable, just like a voltmeter is used by an electrician to examine what's going on inside an electric cable (but at a higher level, of course). In the past, such tools were either very expensive, proprietary, or both. However, with the advent of Ethereal, all that has changed. Ethereal is perhaps one of the best open source packet analyzers available today.

Here are some examples people use Ethereal for: network administrators use it to troubleshoot network problems network security engineers use it to examine security problems developers use it to debug protocol implementations people use it to learn network protocol internals Beside these examples, Ethereal can be helpful in many other situations too.

The following are some of the many features Ethereal provides: Available for UNIX and Windows. Capture live packet data from a network interface. Display packets with very detailed protocol information. Open and Save packet data captured. Import and Export packet data from and to a lot of other capture programs. Filter packets on many criteria. Search for packets on many criteria. Colorize packet display based on filters. Create various statistics. ... and a lot more! However, to really appreciate its power, you have to start using it. shows Ethereal having captured some packets and waiting for you to examine them.

Despite its name, Ethereal can capture traffic from network media other than Ethernet. Which media types are supported, depends on many things like the operating system you are using. An overview of the supported media types can be found at: .

Ethereal can open packets captured from a large number of other capture programs. For a list of input formats see .

Ethereal can save packets captured in a large number of formats of other capture programs. For a list of output formats see .

There are protocol decoders (or dissectors, as they are known in Ethereal) for a great many protocols: see .

Ethereal is an open source software project, and is released under the GNU General Public Licence (GPL). You can freely use Ethereal on any number of computers you like, without worrying about license keys or fees or such. In addition, all source code is freely available under the GPL. Because of that, it is very easy for people to add new protocols to Ethereal, either as plugins, or built into the source, and they often do!

Here are some things Ethereal does not provide: Ethereal isn't an intrusion detection system. It will not warn you when someone does strange things on your network that he/she isn't allowed to do. However, if strange things happen, Ethereal might help you figure out what is really going on. Ethereal will not manipulate things on the network, it will only "measure" things from it. Ethereal doesn't send packets on the network or do other active things (except for name resolutions, but even that can be disabled).

Ethereal currently runs on most UNIX platforms and various Windows platforms. It requires GTK+, GLib, libpcap and some other libraries in order to run. If a binary package is not available for your platform, you should download the source and try to build it. Please report your experiences to &EtherealDevMailList;. Binary packages are available for at least the following platforms:

Apple Mac OS X BeOS FreeBSD HP-UX IBM AIX NetBSD OpenBSD SCO UnixWare/OpenUnix SGI Irix Sun Solaris/Intel Sun Solaris/Sparc Tru64 UNIX (formerly Digital UNIX)

Debian GNU/Linux Gentoo Linux IBM S/390 Linux (Red Hat) Mandrake Linux PLD Linux Red Hat Linux Rock Linux Slackware Linux Suse Linux

Windows Me / 98 / 95 Windows Server 2003 / XP / 2000 / NT 4.0

You can get the latest copy of the program from the Ethereal website: &EtherealDownloadPage;. The website allows you to choose from among several mirrors for downloading. A new Ethereal version will typically become available every 4-8 weeks. If you want to be notified about new Ethereal releases, you should subscribe to the ethereal-announce mailing list. You will find more details in .

William Shakespeare wrote: "A rose by any other name would smell as sweet." And so it is with Ethereal, as there appears to be two different ways that people pronounce the name. Some people pronounce it ether-real, while others pronounce it e-the-real, as in ghostly, insubstantial, etc. You are welcome to call it what you like, as long as you find it useful. The FAQ gives the official pronunciation as "e-the-real".

In late 1997, Gerald Combs needed a tool for tracking down networking problems and wanted to learn more about networking, so he started writing Ethereal as a way to solve both problems. Ethereal was initially released, after several pauses in development, in July 1998 as version 0.2.0. Within days, patches, bug reports, and words of encouragement started arriving, so Ethereal was on its way to success. Not long after that Gilbert Ramirez saw its potential and contributed a low-level dissector to it. In October, 1998, Guy Harris of Network Appliance was looking for something better than tcpview, so he started applying patches and contributing dissectors to Ethereal. In late 1998, Richard Sharpe, who was giving TCP/IP courses, saw its potential on such courses, and started looking at it to see if it supported the protocols he needed. While it didn't at that point, new protocols could be easily added. So he started contributing dissectors and contributing patches. The list of people who have contributed to Ethereal has become very long since then, and almost all of them started with a protocol that they needed that Ethereal did not already handle. So they copied an existing dissector and contributed the code back to the team.

Ethereal was initially developed by Gerald Combs. Ongoing development and maintenance of Ethereal is handled by the Ethereal team, a loose group of individuals who fix bugs and provide new functionality. There have also been a large number of people who have contributed protocol dissectors to Ethereal, and it is expected that this will continue. You can find a list of the people who have contributed code to Ethereal by checking the about dialog box of Ethereal, or at the authors page on the Ethereal web site. Ethereal is an open source software project, and is released under the GNU General Public Licence (GPL). All source code is freely available under the GPL. You are welcome to modify Ethereal to suit your own needs, and it would be appreciated if you contribute your improvements back to the Ethereal team. You gain three benefits by contributing your improvements back to the community: Other people who find your contributions useful will appreciate them, and you will know that you have helped people in the same way that the developers of Ethereal have helped people. The developers of Ethereal might improve your changes even more, as there's always room for improvements. Or they may implement some advanced things on top of your code, which can be useful for yourself too. The maintainers and developers of Ethereal will maintain your code as well, fixing it when API changes or other changes are made, and generally keeping it in tune with what is happening with Ethereal. So if Ethereal is updated (which is done often), you can get a new Ethereal version from the website and your changes will already be included without any effort for you. The Ethereal source code and binary kits for some platforms are all available on the download page of the Ethereal website: &EtherealDownloadPage;.

If you have problems, or need help with Ethereal, there are several places that may be of interest to you (well, beside this guide of course).

You will find lot's of useful information on the Ethereal homepage at &EtherealWebSite;.

The Ethereal Wiki at &EtherealWikiPage; provides a wide range of information related to Ethereal and packet capturing in general. You will find a lot of information not part of this user's guide. For example, there is an explanation how to capture on a switched network, an ongoing effort to build a protocol reference and a lot more. And best of all, if you would like to contribute your knowledge on a specific topic (maybe a network protocol you know well), you can edit the wiki pages by simply using your webbrowser.

The "Frequently Asked Questions" will list often asked questions and the corresponding answers. Before sending any mail to the mailing lists below, be sure to read the FAQ, as it will often answer the question(s) you might have. This will save yourself and others a lot of time (keep in mind that a lot of people are subscribed to the mailing lists). You will find the FAQ inside Ethereal by clicking the menu item Help/Contents and selecting the FAQ page in the upcoming dialog. An online version is available at the ethereal website: &EtherealFAQPage;. You might prefer this online version, as it's typically more up to date and the HTML format is easier to use.

There are several mailing lists of specific Ethereal topics available: ethereal-announce This mailing list will inform you about new program releases, which usually appear about every 4-8 weeks. ethereal-users This list is for users of Ethereal. People post questions about building and using Ethereal, others (hopefully) provide answers. ethereal-dev This list is for Ethereal developers. If you want to start developing a protocol dissector, join this list. You can subscribe to each of these lists from the Ethereal web site: &EtherealWebSite;. Simply select the mailing lists link on the left hand side of the site. The lists are archived at the Ethereal web site as well. You can search in the list archives to see if someone asked the same question some time before and maybe already got an answer. That way you don't have to wait until someone answers your question.

Before reporting any problems, please make sure you have installed the latest version of Ethereal. When reporting problems with Ethereal, it is helpful if you supply the following information: The version number of Ethereal and the dependent libraries linked with it, eg GTK+, etc. You can obtain this with the command ethereal -v. Information about the platform you run Ethereal on. A detailed description of your problem. If you get an error/warning message, copy the text of that message (and also a few lines before and after it, if there are some), so others may find the place where things go wrong. Please don't give something like: "I get a warning while doing x" as this won't give a good idea where to look at. Do not send large files (>100KB) to the mailing lists, just place a note that further data is available on request. Large files will only annoy a lot of people on the list who are not interested in your specific problem. If required, you will be asked for further data by the persons who really can help you. If you send captured data to the mailing lists, be sure they don't contain any sensitive or confidential information like passwords or such.

When reporting crashes with Ethereal, it is helpful if you supply the traceback information (besides the information mentioned in "Reporting Problems"). You can obtain this traceback information with the following commands: & bt.txt backtrace ^D $ ]]> Type the characters in the first line verbatim! Those are back-tics there! backtrace is a gdb command. You should enter it verbatim after the first line shown above, but it will not be echoed. The ^D (Control-D, that is, press the Control key and the D key together) will cause gdb to exit. This will leave you with a file called bt.txt in the current directory. Include the file with your bug report. If you do not have gdb available, you will have to check out your operating system's debugger. You should mail the traceback to the &EtherealDevMailList; mailing list.

The Windows distributions don't contain the symbol files (.pdb), because they are very large. For this reason it's not possible to create a meaningful backtrace file from it. You should report your crash just like other problems, using the mechanism described above.