what constitutes high CPU usage and how much can my router handle?

Unanswered Question
May 15th, 2007

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?

I have this problem too.
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spremkumar Tue, 05/15/2007 - 19:28

Hi Johny

Cisco has clearly given the specs on how much each router model will be able to handle and also the processing speed of the boxes.

20% usage at this point of time may not be a concern but when it nears or tops over 50% always then you need to start verifying actual traffic.

you can refer the below guide to have a fair idea on how much load each device is capable of handling.


In some case you may have some worms/virus traffic which is being handled by the CPU and actually hogs up the performance of the device..

Martin Ermel Wed, 05/16/2007 - 03:39

the attached paper is really a good summery, but where did you get it? I cant find it on Ciscos website. Could you post a link?


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