MRTG: Install and Configure in centOS

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. You need the following packages:

Requirements:
mrtg : Multi Router Traffic Grapher
net-snmp and net-snmp-utils : SNMP (Simple Network Management Protocol) is a protocol used for network management. The NET-SNMP project includes various SNMP tools. net-snmp package contains the snmpd and snmptrapd daemons, documentation, etc. Net-snmp-utils package

1:Install MRTG

Type the following command to install packages using yum command under CentOS / Fedora Linux:

# yum install mrtg net-snmp net-snmp-utils

2:Configure snmpd

If you need to monitor localhost including interface and other stuff such as CPU, memory etc, configure snmpd. Open /etc/snmp/snmpd.conf, enter:

# vi /etc/snmp/snmpd.conf

Update it as follows to only allow access from localhost:

com2sec local     localhost           public
group MyRWGroup v1         local
group MyRWGroup v2c        local
group MyRWGroup usm        local
view all    included  .1                               80
access MyRWGroup ""      any       noauth    exact  all    all    none
syslocation Your_Location
syscontact Root <your@emailaddress.com>

Save and close the file.

# chkconfig snmpd on
# service snmpd restart

Make sure you see interface IP, by running the following command:
# snmpwalk -v 1 -c public localhost IP-MIB::ipAdEntIfIndex

Sample Outputs:

IP-MIB::ipAdEntIfIndex.123.xx.yy.zzz = INTEGER: 2
IP-MIB::ipAdEntIfIndex.127.0.0.1 = INTEGER: 1

3:Configure MRTG

Use cfgmaker command to creates /etc/mrtg/mrtg.cfg file.

# cfgmaker --global 'WorkDir: /var/www/mrtg' --output /etc/mrtg/mrtg.cfg public@localhost

--global 'WorkDir: /var/www/mrtg' : add global config entries i.e. set workdir to store MRTG graphs.
--output /etc/mrtg/mrtg.cfg: configr output filename

public@localhost: public is the community name and it is by default. Using the wrong community name you will give no response from the device. localhost is the DNS name or the IP number of an SNMP-managable device.

Finally, run indexmaker to create web pages which display the status of an array of mrtg interface status pages

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

4: Verify Cron Job

/etc/cron.d/mrtg runs mrtg command to monitor the traffic load on network links

# cat /etc/cron.d/mrtg

Sample Output

*/5 * * * * root LANG=C LC_ALL=C /usr/bin/mrtg /etc/mrtg/mrtg.cfg --lock-file /var/lock/mrtg/mrtg_l --confcache-file
/var/lib/mrtg/mrtg.ok

# chkconfig --list crond

If it is off in run level # 3, run the following to turn on crond service:

# chkconfig crond on
# service crond on

View mrtg graphs:
You need Apache web server to view graphs:

# yum install httpd
# chkconfig httpd on
# service httpd on

Go to a web browser and type
http://your-ip.add.ress/mrtg/