SNMP and MRTG on Sarge quick start

SNMP and MRTG on Sarge quick start
Firstly, you need an SNMP server to provide network interface statstics on demand:

1. The SNMP server. This allows access via the SNMP protocol to the system’s network interface statistics and other data.
2. The MRTG (Multi router traffic grapher). This is a large Perl script which polls the SNMP server and accumulates information about network usage. This runs periodically from cron and generates graphs at defined intervals

Please note that you can collect and graph anything with these – they are not limited to network statistics. Not only that, you can manage many aspects of your server with SNMP.

Please make sure you have apache or apache2 installed for this to work.

SNMP server configuration

Firstly, you need an SNMP server to provide network interface statstics on demand:

# apt-get install snmpd

You need to edit the configuration for this as it does not allow any connections by default. With your favourite editor, edit:

/etc/snmp/snmpd.conf

Comment out the following (prefix with #):

com2sec paranoid default public

Insert the following underneath the commented out section:

com2sec readonly default public

That gives anyone with access to the SNMP server read-only access to the public community. This is the one that contains the interface statistics.

To apply the changes, restart snmpd:

/etc/init.d/snmpd restart

Make sure you firewall off any SNMP related ports so that you don’t get any unwanted visitors (check netstat and /etc/services for port information).

Installation of MRTG

MRTG is the main collection and graphing component of the traffic monitoring solution I am presenting here. Firstly, install MRTG:

# apt-get install mrtg

You can manually or automatically generate the configuration file for mrtg. I would recommend doing it automatically as it is a lot easier. Issue the following command:

# cfgmaker --global 'WorkDir: /var/www/mrtg' \
    --output /etc/mrtg.cfg public@127.0.0.1

This will generate the configuration file. You then need to make an index file which contains a list of all of your interfaces. Issue the following command:

# indexmaker /etc/mrtg.cfg --columns=1 \
    --output /var/www/mrtg/index.html

You will now need to execute mrtg manually 3 times to create the required database files. Issue the following command 3 times sequentially. On the third run, you should see no errors being reported:

# mrtg

This is executed every 5 minutes by cron. The cron job was added by dpkg for you so you do not have to configure

by:debian-administration.org

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