How to Install and Configure MRTG on Ubuntu 18.04/20.04

MRTG (Multi Router Traffic Grapher) is an open-source tool written in Perl used for monitoring and measuring the traffic load on network links and presenting data in graphical form. This tool helps you trace and troubleshoot network anomalies like Network traffic spikes at odd hours.

MRTG works with all network devices that support SNMP protocol.  It monitors SNMP network devices and draws pretty pictures showing how much traffic has passed through each interface. MRTG runs on Unix/Linux, Windows, and Netware systems.

In this post, we're going to look at how to Install and Configure MRTG on Ubuntu 18.04/20.04.

MRTG Prerequisites

You need to have Apache installed before you can run MRTG on your machine. On Ubuntu 18.04, you can easily install Apache by pulling the package from the official repository.

$ sudo apt install apache2

Install snmp packages for Ubuntu:

$ sudo apt install snmpd snmp

To configure SNMP, I like enabling full access from localhost:

$ sudo vim /etc/snmp/snmpd.conf

Add the following snmp community string to snmpd.conf file:

rocommunity public localhost

You need to restart snmpd service for the change to be effected.

$ sudo systemctl restart snmpd

By default, SNMP listens to localhost. You can verify what port or IP to which SNMP is listening using the ss command.

Install MRTG on Ubuntu 18.04/20.04

All prereqs are okay, so we can install MRTG on Ubuntu by running the command:

$ sudo apt install mrtg

Accept any popup prompt and click yes to start the installation.

Configuring MRTG

Once the installation process is complete, you need to configure it before you can start monitoring target devices. We'll set MRTG working directory to be /var/www/mrtg

$ sudo mkdir /var/www/mrtg

Make sure to change owner of this directory to www-data, which is the default user account for Apache web server.

$ sudo chown -R www-data:www-data /var/www/mrtg

Then edit /etc/mrtg.conf to set Working directory:

$ sudo cat /etc/mrtg.cfg | grep -v "^#"

Output:

WorkDir: /var/www/mrtg
WriteExpires: Yes
Title[^]: Traffic Analysis for

Rebuild MRTG configuration from modified file:

$ sudo cfgmaker public@localhost > /etc/mrtg.cfg

Output:

--base: Get Device Info on public@localhost:
--base: Vendor Id: Unknown Vendor - 1.3.6.1.4.1.8072.3.2.10
--base: Populating confcache
--base: Get Interface Info
--base: Walking ifIndex
--snpd: public@localhost: -> 1 -> ifIndex = 1
--snpd: public@localhost: -> 2 -> ifIndex = 2
--snpd: public@localhost: -> 3 -> ifIndex = 3
--base: Walking ifType
--snpd: public@localhost: -> 1 -> ifType = 24
--snpd: public@localhost: -> 2 -> ifType = 6
--snpd: public@localhost: -> 3 -> ifType = 6
--base: Walking ifAdminStatus
--snpd: public@localhost: -> 1 -> ifAdminStatus = 1
--snpd: public@localhost: -> 2 -> ifAdminStatus = 1
--snpd: public@localhost: -> 3 -> ifAdminStatus = 1
--base: Walking ifOperStatus
--snpd: public@localhost: -> 1 -> ifOperStatus = 1
--snpd: public@localhost: -> 2 -> ifOperStatus = 1
--snpd: public@localhost: -> 3 -> ifOperStatus = 1
--base: Walking ifMtu
--snpd: public@localhost: -> 1 -> ifMtu = 65536
--snpd: public@localhost: -> 2 -> ifMtu = 1500
--snpd: public@localhost: -> 3 -> ifMtu = 1500
--base: Walking ifSpeed
--snpd: public@localhost: -> 1 -> ifSpeed = 10000000
--snpd: public@localhost: -> 2 -> ifSpeed = 0
--snpd: public@localhost: -> 3 -> ifSpeed = 0

$ ls /var/www/mrtg/
index.html mrtg-l.png mrtg-m.png mrtg-r.png

Create index file for web server:

$ sudo indexmaker /etc/mrtg.cfg > /var/www/mrtg/index.html

The last thing to do is create a VirtualHost file for the site.

$ sudo vim /etc/apache2/sites-available/mrtg.conf

Add the following to this new file:

Alias /mrtg "/var/www/mrtg/"
​<Directory "/var/www/mrtg/">
 ​Options None
​ AllowOverride None
​ Require all granted
​</Directory>

Enable the site and reload apache service.

$ sudo sudo a2ensite mrtg

Reload Apache service:

$ sudo systemctl reload apache2

Accessing MRTG UI

Head over to http://ip-address/mrgt or http://servername/mrtg to access MRTG web interface. Interface monitoring should start showing traffic:

There is also default daily graph for an interface by default.

You can configure MRTG to monitor other things like RAM, CPU usage, Swap, Disk e.t.c.

Configure MRTG to poll metrics every X minutes

I'm going to create a cron job which checks for changes on the configuration file and generate new png images that can be viewed on the web interface. Make sure to create the cron job as the root user.

# crontab -e

*/5 * * * * root LANG=C LC_ALL=C /usr/bin/mrtg /etc/mrtg.cfg

This will be executed every five minutes.

Conclusion

In this tutorial, we learned how to install and configure MRTG on Ubuntu 18.04/20.04.

Thanks for reading, please provide your feedback and suggestion in the comment section.