IntroductionWhat is Ethereal?
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.
Some intended purposes
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.
Features
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.
Live capture from many different network media
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:
.
Import files from many other capture programs
Ethereal can open packets captured from a large number of
other capture programs. For a list of input formats see
.
Export files for many other capture programs
Ethereal can save packets captured in a large number of formats of
other capture programs. For a list of output formats see
.
Many protocol decoders
There are protocol decoders (or dissectors, as they are
known in Ethereal) for a great many protocols:
see .
Open Source Software
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!
What Ethereal is not
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).
Platforms Ethereal runs on
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:
UnixApple Mac OS XBeOSFreeBSDHP-UXIBM AIXNetBSDOpenBSDSCO UnixWare/OpenUnixSGI IrixSun Solaris/IntelSun Solaris/SparcTru64 UNIX (formerly Digital UNIX)LinuxDebian GNU/LinuxGentoo LinuxIBM S/390 Linux (Red Hat)Mandrake LinuxPLD LinuxRed Hat LinuxRock LinuxSlackware LinuxSuse LinuxMicrosoft WindowsWindows Me / 98 / 95Windows Server 2003 / XP / 2000 / NT 4.0Where to get Ethereal?
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 .
A rose by any other name
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".
A brief history of Ethereal
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.
Development and maintenance of Ethereal
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;.
Reporting problems and getting help
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).
Website
You will find lot's of useful information on the Ethereal homepage at
&EtherealWebSite;.
Wiki
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.
FAQ
The "Frequently Asked Questions" will list often asked questions and
the corresponding answers.
Read the FAQ!
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.
Mailing Lists
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.
Tip!
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.
Reporting ProblemsNote!
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.
Don't send large files!
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.
Don't send confidential information!
If you send captured data to the mailing lists, be sure they don't contain
any sensitive or confidential information like passwords or such.
Reporting Crashes on UNIX/Linux platforms
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.
Reporting Crashes on Windows platforms
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.