We recently moved from a creaky 3640 up to a nice new 2811. It sits at the middle of our LAN, run two TI connections to two remote sites, a 16 line modem bank for dial in access (never actually used to anywhere near full capacity. Usually only 2 or 3 lines in usa) and routes all Internet traffic from all three sites to the gateway firewall router. We are a very small college so the traffic is not all that enormous.

Right now with a minimal setup and a couple of minimal access lists CPU usage is around 20%.

I would like to add vlans and comprehensive access lists to our network. But this would increase the routers workload.

How can I figure out how much it can take and decide when its had enough?