Assume that, If you have installed MRTG  for monitoring network device(switch) on Linux system, also you would like to monitoring MRTG on Nagios just following below steps,

Its Nagios shows monitoring network status from MRTG ports log,

How to Configure:

Login into your Nagios Server,create a new file mrtgmonitor.cfg for configure mrtg host. File creation location already discussed on nagios server installation post.

​# cd /usr/local/nagios/etc/servers

# touch mrtgmonitor.cfg

Note : /var/www/html/mrtg/mrtg-192.168.0.2_1.log and /var/www/html/mrtg/192.168.0.2_2.log this is mrtg log files.

Add below lines



define host{

        use                     MRTG-SERVER

        host_name               host.mrtg-server.com

        alias                   host.mrtg-server

        address                 192.168.0.105

       }



define service{

        use                             generic-service

        host_name                       host.mrtg-server.com

        service_description             PORT-1

        check_command

check_nrpe!check_mrtg_1!/var/www/html/mrtg/mrtg-192.168.0.2_1.log!MAX!5,10!6,11!mbyte!

        }



define service{

        use                             generic-service

        host_name                       host.mrtg-server.com

        service_description             PORT-2

        check_command

check_nrpe!check_mrtg_2!/var/www/html/mrtg/192.168.0.2_2.log!MAX!10,20!11,21!mbyte!

        }


Save the file :wq!

then go to /usr/local/nagios/etc/objects/ path and open the command.cfg file.
 
# cd /usr/local/nagios/etc/objects

# vim command.cfg


#command definition #

define command{

command_name check_mrtgtraf.pl

command_line $USER1$/check_mrtgtraf.pl -L $ARG1$ -F $ARG2$ -w $ARG3$ -c $ARG4$ -u $ARG5$

}


Finally in Nagios server side configuration completed, then test the configuration and restart it.
 
# /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

# /etc/init.d/nagios restart


Running configuration check...

Stopping nagios:. done.

Starting nagios: done.


Client side configure (MRTG Installed Server):

Download the check_mrtgtraf.pl file from Nagios   and move the script to /usr/loca/nagios/libexec directory 

Before add the command in nrpe.cfg file check on your terminal whether working on or not?
 
#  /usr/local/nagios/libexec/check_mrtgtraf.pl -FUNCT AVG -LOG /var/www/html/mrtg/yourmrtg_port_log.log -WARN 10,10 -CRIT 15,15 -u megabytes
 Traffic OK: AVG. in = 4.32478332519531 Mbyte/s, AVG. out = 1.71255493164062 Mbyte/s. 


Now you will update in nrpe.cfg file
 
# cd /usr/local/nagios/etc/

# vim nrpe.cfg

command[check_switch]= /usr/local/nagios/libexec/check_mrtgtraf.pl -FUNCT AVG -LOG /var/www/html/mrtg/yourmrtg_port_log.log -WARN 10,10 -CRIT 15,15 -u megabytes


Now, save that file :wq!