I found out about Cacti from work. Somebody installed it to monitor the SIP stats of the Solaris boxen.

Creating your own monitors is a bitch! (it's hard work) but for the standard stuff, you can create a device first, and make it a local linux box, and add the standard linux things like:

• Number of users logged in
• Number of processes
• Memory usage

But then if you change the template to be an SNMP host (and make sure you have snmp installed and running...) you can add things like:

• Traffic monitors for all interfaces
• Other things that use SNMP.

Just be careful on Gentoo to:

• emerge both php and mod_php, and if you upgrade one, you must do the other.
• make sure that you compile both php and mod_php with snmp support.

I used the mrtg howto on the Gentoo Forums as a guide to setting up snmp at least.

Also, Cacti uses cron for polling. The notes after the ebuild suggest installing a line in /etc/crontab.

You will need to run the following commands to make sure that the data and log files can be written:

# chmod -R apache:apache log rrd

Make sure you first install Cacti, to change the host to be a Generic SNMP host and change the SNMP community to be Public.

You should then be able to add traffic graphs :)