High CPU load on Cisco 2921

[wggfilonenko1]

Hi.

We are seeing a high CPU load on the router (Cisco 2921). All other problems are a consequence of this.
At the same time, there is only one high-load process in the show proc cpu command output:
CPU utilization for five seconds: 99%/47%; one minute: 95%; five minutes: 95%
172 57333076 87035101 658 42.46% 41.33% 40.21% 0 IP Input

This is a lot, but it is far from 100%. How can we determine the cause of the CPU load?

[Joseph W. Doherty]

". . .the current setup has been working for a long time with this load and the problems started recently."

Possibly a change in what's been routine traffic, and/or downstream MTU considerations?

I notice you're using tunnels, and although you using "ip tcp adjust-mss 1376", that has no effect on UDP traffic, like video streams, which can create fragmentation CPU performance issues, which might be accounted as IP Input.  (NB: I've seen such newly created streams really chew up a small ISR's CPU.)

Further, although you're using "ip tcp adjust-mss 1376", there's more, I believe (NB: I haven't carefully studied your config) to optimize tunnels that impact MTU (NB: often, though, all the techniques don't have much control over typical UDP stream fragmentation).