mrtg - What is MRTG ?


   The Multi Router Traffic Grapher (MRTG) is a tool to monitor the
   traffic load on network links.  MRTG generates HTML pages containing
   PNG images which provide a LIVE visual representation of this traffic.
   Check to see what it does.

   Go to for all the details about mrtg.


       MRTG works on most UNIX platforms and Windows NT.

       MRTG is written in Perl and comes with full source.

   Portable SNMP
       MRTG Uses a highly portable SNMP implementation written entirely in
       Perl (thanks to Simon Leinen). There is no need to install any
       external SNMP package.

   SNMPv2c support
       MRTG can read the new SNMPv2c 64bit counters. No more counter

   Reliable Interface Identification
       Router interfaces can be identified by IP address, description and
       ethernet address in addition to the normal interface number.

   Constant size Logfiles
       MRTG's logfiles do NOT grow thanks to the use of a unique data
       consolidation algorithm.

   Automatic Configuration
       MRTG comes with a set of configuration tools which make
       configuration and setup very simple.

       Time critical routines are written in C (thanks to the initiative
       of Dave Rand my Co-Author).

   GIF free Graphics
       Graphics are generated directly in PNG format using the GD library
       by Thomas Boutell.

       The look of the webpages produced by MRTG is highly configurable.

       MRTG has built-in hooks for using RRDtool. If you are strapped for
       performance this may help.


   MRTG consists of a Perl script which uses SNMP to read the traffic
   counters of your routers and a fast C program which logs the traffic
   data and creates beautiful graphs representing the traffic on the
   monitored network connection. These graphs are embedded into webpages
   which can be viewed from any modern Web-browser.

   In addition to a detailed daily view, MRTG also creates visual
   representations of the traffic seen during the last seven days, the
   last five weeks and the last twelve months. This is possible because
   MRTG keeps a log of all the data it has pulled from the router. This
   log is automatically consolidated so that it does not grow over time,
   but still contains all the relevant data for all the traffic seen over
   the last two years.  This is all performed in an efficient manner.
   Therefore you can monitor 200 or more network links from any halfway
   decent UNIX box.

   MRTG is not limited to monitoring traffic, though.  It is possible to
   monitor any SNMP variable you choose. You can even use an external
   program to gather the data which should be monitored via MRTG. People
   are using MRTG, to monitor things such as System Load, Login Sessions,
   Modem availability and more. MRTG even allows you to accumulate two or
   more data sources into a single graph.


   In 1994 I was working at a site where we had one 64kbit line to the
   outside world. Obviously, everybody was interested in knowing how the
   link was performing. So I wrote a quick hack which created a constantly
   updated graph on the web that showed the traffic load on our Internet
   link. This eventually evolved into a rather configurable Perl script
   called MRTG-1.0 which I released in spring 1995. After a few updates, I
   left my job at DMU to start work at the Swiss Federal Institute of
   Technology. Due to lack of time I had to put MRTG aside. One day in
   January of 1996, I received email from Dave Rand asking if I had any
   ideas why MRTG was so slow. Actually, I did. MRTG's programming was not
   very efficient and it was written entirely in Perl. After a week or so,
   Dave wrote back to me and said he had tried what I had suggested for
   improving MRTG's speed. Since the changes did not help much, he had
   decided to rewrite the time-critical sections of MRTG in C. The code
   was attached to his email. His tool increased the speed of MRTG by a
   factor of 40! This got me out of my 'MRTG ignorance' and I started to
   spend my spare time developing of MRTG-2.

   Soon after MRTG-2 development had begun I started to give beta copies
   to interested parties. In return I got many feature patches, a lot of
   user feedback and bug fixes. The product you are getting now wouldn't
   be in this state if it hadn't been for the great contributions and
   support I received from of many people. I would like to take this
   opportunity to thank them all. (See the files CHANGES for a long list
   of folk people who helped to make MRTG what it is today.)


   Mrtg is also the name of the script you have to run to poll data and
   generate the graphs. Most configuration is set through the
   configuration file; some command-line options exist all the same.

   --user username  and --group groupname
       Run as the given user and/or group. (Unix Only)

   --lock-file filename
       Use an alternate lock-file (the default is to use the
       configuration-file appended with "_l").

   --confcache-file filename
       Use an alternate confcache-file (the default is to use the
       configuration-file appended with ".ok")

   --logging filename|eventlog
       If this is set to writable filename, all output from mrtg
       (warnings, debug messages, errors) will go to filename. If you are
       running on Win32 you can specify eventlog instead of a filename
       which will send all error to the windows event log.

       NOTE:Note, there is no Message DLL for mrtg. This has the side
       effect that the windows event logger will display a nice message
       with every entry in the event log, complaing about the fact that
       mrtg has no message dll. If any of the Windows folks want to
       contribute one, they are welcome.

       Put MRTG into the background, running as a daemon. This works the
       same way as the config file option, but the switch is required for
       proper FHS operation (because /var/run is writable only by root)

       Configure all mrtg paths to conform to the FHS specification;

       Only check the cfg file for errors. Do not do anything.

       Define the name and path of the pid file for mrtg running as a

       Only update the logfile, do not produce graphics or html pages

       Enable debug options. The argument of the debug option is a comma
       separated list of debug values:

        cfg  - watch the config file reading
        dir  - directory mangeling
        base - basic program flow
        tarp - target parser
        snpo - snmp polling
        fork - forking view
        time - some timing info
        log  - logging of data via rateup or rrdtool




   Learn more about MRTG by going to the mrtg home page on:


   Tobias Oetiker <> and many contributors


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