I have an existing basic MRTG setup done using cfgmaker to monitor the traffic of our Cisco router.
I'd like to add configuration sections to mrtg to have it monitor the CPU usage (min/avg/max if possible) and memory utilization of the router.
I'm not quite sure where to start. Can somebody show an example of an MRTG config they've done for these parameters?
Router is running c2600-ik9o3s3-mz.123-26, in case it matters.
The Cisco SNMP Object Navigator is going to be your friend in these kinds of questions. You can look up your image name to find all supported MIBs, and more or less copy and modify an existing cfgmaker-generated stanza to graph the particular value you're interested in.
The good news is that your question is already answered over on the MRTG mailing list: "Cisco 2600 & 2950 cpu usage".
I understand that this is somewhat of a "halfway" answer because it suggests a completely different solution than what you're using, but you did say in the question that you have a 'basic' MRTG config... this implies it wouldn't be that hard to move to something else. My suggestion uses the 'successor' to MRTG (rrdtool) for its graphing, and was made by the same person that made MRTG (Tobi Oetiker if you're curious)
Have you looked at Cacti? It takes some getting used to, but I've done a lot of graphing and monitoring that impressed everyone from developers to network engineers to management, including monitoring an array of Cisco routers, switches and firewalls. I personally know there's a Cacti template already built for a Cisco 2600 that will monitoring just about everything you could possibly be looking for... bandwidth, temperature (if your chassis supports it), CPU, memory, number of IPSec tunnels that are up (if you have any), number of NAT translations built, the list goes on and on.
Here are some examples of Cacti templates that are already built... some of these posts answer your question as well, because they discuss the SNMP OIDs needed:
http://forums.cacti.net/about5603.html (Cisco memory and CPU)
