CS & IT Solutions

1. Introduction
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. Its source is written in Perl and C which means that it can be installed in every Operating System we like. We will also need SNMP daemon (Simple Network Management Protocol) which gives us information for a network. The following installation was accomplished under Linux and specifically Fedora Core 6. With some little changes it can be used and under other distros.

2. SNMP server

2.1 Installation

Initially we install the packets needed for SNMP. Yum makes this job a lot easier.

Next we make snmpd service to start automatically for the runlevels we want.
# yum install net-snmp-utils net-snmp

And we start the server.
# chkconfig --level 345 snmpd


We can see that it is running in port 199.
# service snmpd start

# netstat -natv | grep ':199'

tcp 0 0 127.0.0.1:199 0.0.0.0:* LISTEN

2.2 Configuration

We run ‘snmpwalk’ which creates a “tree” of information for our network.

If you see an output like this one you may proceed with the MRTG installation. Else you should make some configuration first.
# 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

We keep a backup of snmpd.conf just in case anything goes wrong

# cp /etc/snmp/snmpd.conf /etc/snmp/snmpd.conf.original

We open it
# nano /etc/snmp/snmpd.conf

And do the follow changes:

* we change this line

com2sec notConfigUser default public

with those

com2sec local localhost public

com2sec mynetwork 10.0.0.0/8 public

where 10.0.0.0/8 we put what our network is

* we change those lines

group notConfigGroup v1 notConfigUser

group notConfigGroup v2c notConfigUser

with those

group MyRWGroup v1 local

group MyRWGroup v2c local

group MyRWGroup usm local

group MyROGroup v1 mynetwork

group MyROGroup v2c mynetwork

group MyROGroup usm mynetwork

* we change those lines

view systemview included .1.3.6.1.2.1.1

view systemview included .1.3.6.1.2.1.25.1.1

with this one

view all included .1 80

* we change this line

access notConfigGroup “” any noauth exact systemview none none

with those

access MyROGroup “” any noauth exact all none none

access MyRWGroup “” any noauth exact all all none

* and finally we change those lines

syslocation Unknown (edit /etc/snmp/snmpd.conf)

syscontact Root (configure /etc/snmp/snmp.local.conf)

with something like this

syslocation Linux, Fedora Core 6

syscontact Root root@localhost

2.3 Check

We restart the server to take affect of the notices

# service snmpd restart

And we run again

# snmpwalk -v 1 -c public localhost IP-MIB::ipAdEntIfIndex

Now we should see something like that

IP-MIB::ipAdEntIfIndex.10.103.0.33 = INTEGER: 2

IP-MIB::ipAdEntIfIndex.127.0.0.1 = INTEGER: 1

Where 10.103.0.33 is your ip address.

3. MRTG

3.1 Installation

We again use yum

# yum install mrtg

3.2 Configuration

We create the folder in which our graphs and html pages will be kept

# mkdir /var/www/html/mrtg/

And we run ‘cfgmaker’ for the configuration file to be created.

# cfgmaker --global "workdir: /var/wwwhtml/mrtg" -ifref=ip --output /etc/mrtg/mrtg.cfg --global 'options[_]: growright,bits' public@localhost

Here you should pay notice to –output /etc/mrtg/mrtg.cfg as long as to public@localhost. With this command we tell MRTG to create a configuration file with the name ‘mrtg.cfg’ for the traffic of our computer (localhost). Instead of localhost you may put the address of any computer you may monitor as long as it runs SNMP.

Next we create our default index page

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

3.2.1 Apache configuration

Next we have to configure apache for MRTG to work correctly. MRTG creates a file ‘mrtg.cfg’ under /etc/httpd/conf.d we contains all the necessary for Apache. We change it to contain the ips we want to have access to our MRTG graphs. Here I have added all my network.

Alias /mrtg /var/www/mrtg
Order deny,allow

Deny from all

Allow from 127.0.0.1 10.0.0.0/8

3.3 Check

We run the following command

In case you get an error like this
# mrtg /etc/mrtg/mrtg.cfg

ERROR: Mrtg will most likely not work properly when the environment

variable LANG is set to UTF-8. Please run mrtg in an environment

where this is not the case. Try the following command to start:

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

you have to run the above command more than once till it runs without any error. This is normal.
# env LANG=C /usr/bin/mrtg /etc/mrtg/mrtg.cfg

23-02-2007 17:28:53, Rateup WARNING: /usr/bin/rateup Can’t remove localhost_2.old updating log file

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

#

Finally we open our browser and type

http://127.0.0.1/mrtg

source here