MRTG is the Multi Router Traffic Grapher: a free utility that graphically displays traffic levels on your network. It provides a quick and useful way of monitoring bandwidth usage, potential bottlenecks and the general ‘health’ of your network all from your web browser.

Available for both Windows and Linux platforms, it can be downloaded free of charge from http://oss.oetiker.ch/mrtg/download.en.html

In order to install MRTG on Linux, the machine will need to be running a web server with Perl support enabled. Select this option when installing the Linux OS.

The GCC compiler will also be required. This can be installed using yum with the following command:

yum install gcc

MRTG also requires the following components:

• SNMP (Simple Network Management Protocol)
• The Graph Drawing Library (GD) – to display graph images
• libPNG – to display the graph images in PNG format
• zlib – to compress the image files

SNMP can be installed through yum by using the following command:

yum install net-snmp-utils net-snmp

To start the SNMP service use the following command:

service snmpd start

To ensure that the SNMP service starts automatically each time the server is powered on, use the following commands:

chkconfig –add snmpd
chkconfig snmpd on

zlib can be downloaded from http://www.gzip.org/zlib
The package will be saved in ‘tar.gz’ format. Extract the contents of the archive with the command:

tar xvfz zlib-x.x.x.tar.gz

Now change to the new directory that has been created and install zlib with the following commands:

./configure
make
make install

libPNG can be downloaded from http://www.libpng.org/pub/png/libpng.html
The package will be saved in ‘tar.gz’ format. Extract the contents of the archive with the command:

tar xvfz libpng-x.x.x.tar.gz

Now change to the new directory that has been created and install libpng with the following commands:

./configure
make
make install

The Graph Drawing library (GD) can be downloaded from http://www.libgd.org/Downloads
The package will be saved in ‘tar.gz’ format. Extract the contents of the archive with the command:

tar xvfz gd-x.x.x.tar.gz

Now change to the new directory that has been created and install GD with the following commands:

./configure
make
make install

MRTG itself can be downloaded using yum, or manually from http://oss.oetiker.ch/mrtg/download.en.html

If you choose to download the package manually, the file will be downloaded in ‘tar.gz’ format. Save it to a directory on the server and extract the contents of the archive file with the following command:

tar xvfz mrtg-x.x.x.tar.gz

Now change to the new directory that has been created and install MRTG with the following commands:

./configure
make
make install

Alternatively download it via yum with the following command:

yum install mrtg

In this article I installed MRTG using yum

Once installed, we need to create the directory that the web site will run in, this is usually in the format http://(server)/mrtg/ , therefore we need to create a directory in /var/www/html/mrtg/
Do this with the following command:

mkdir /var/www/html/mrtg/

Now change directory to /var/www/mrtg/

MRTG must now be configured with a ‘.cfg’ file to instruct MRTG which network resource(s) to monitor. Create the cfg file by issuing the following command:

cfgmaker –global ‘WorkDir: /var/www/html/mrtg’ –output /etc/mrtg/mrtg.cfg public@192.168.0.1 

(where 192.168.0.1 is the IP address of the router you wish to monitor via SNMP)

Now an index.html file must be created for the MRTG web site. Do this by issuing the following command:

indexmaker --output=/var/www/html/mrtg/index.html /etc/mrtg/mrtg.cfg

Launch MRTG with the following command:

env  LANG=C /usr/bin/mrtg /etc/mrtg/mrtg.cfg

Now you can browse to the MRTG web page from your browser: http://(mrtg_server)/mrtg

Hopefully, if all has gone according to plan, you will see something like this: