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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. 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. MRTG uses 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. MRTG (Multi Router Traffic Grapher) is an application that allows us to observe the traffic of a network. It generates html pages with graphs which are refreshed according to our network’s current state. Make sure SNMP server is working. Without proper working SNMP Server, mrtg will not work. Therefore, first step is making sure snmp up and running.
Type the following rpm command to find out, if snmp server installed or not
# rpm -qa | grep snmp
Determine if snmp server is running or not
# ps -aux | grep snmp
root 5512 0.0 2.3 5872 3012 pts/0 S 22:04 0:00 /usr/sbin/snmpd
Install SNMP using the following command as a root user
# yum install net-snmp-utils net-snmp
# service snmpd start
Make sure snmpd service starts automatically, when linux comes us (add snmpd service):
# chkconfig snmpd on
Check snmp server configured properly
# snmpwalk -v 1 -c public localhost IP-MIB::ipAdEntIfIndex
ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1
ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.0.3 = 2
Mrtg software may install during initial installation; you can verify if MRTG installed or not with the following RPM command:
#rpm -qa | grep mrtg
#yum install mrtg
(a) Create a document root to store mrtg graphs/html pages for Apache web-server, enter:
# mkdir -p /var/www/html/mymrtg/
(b) Run any one of the following cfgmaker command to create mrtg configuration file:
# cfgmaker --global 'WorkDir: /var/www/html/mymrtg' --output /etc/mrtg/mymrtg.cfg public@localhost
OR (make sure FQDN resolves. In the following example I'm using rh9.test.com i.e. my router's FQDN address)
# cfgmaker --global 'WorkDir: /var/www/html/mymrtg' --output /etc/mrtg/mymrtg1.cfg email@example.com
(c) Create a default index page for your MRTG configuration, run:
# indexmaker --output=/var/www/html/mymrtg/index.html /etc/mrtg/mymrtg.cfg
(d) Copy all tiny png files to your mrtg path, run:
# cp -av /var/www/html/mrtg/*.png /var/www/html/mymrtg/
First test run for mrtg
(a) Run mrtg command from command line with your configuration file, enter:
# mrtg /etc/mrtg/mymrtg.cfg
Note: You may get few warning message for the first time; please ignore them.
Create crontab entry so that mrtg graph / images get generated every 5 minutes
# crontab -e
Add mrtg cron job entry to configuration file (append following line to it)
*/5 * * * * /usr/bin/mrtg /etc/mrtg/mymrtg.cfg --logging /var/log/mrtg.log
Close and save file. You are done with MRTG configuration.
You do not want to give access to everyone to your snmp server for security reasons. SNMP server uses UDP port # 161 and 162 for communication. Use Linux IPTABLES firewall command to restrict access to your SNMP server.