High CPU on 2811 but no visible process that causes it

[kasper123]

We have a cisco 2811 that we use to terminate 2 VPN's and to get access to internet.

Several times a day there is high CPU on the router but I can't seem to be able to find what causes it.

Router#show processes cpu sorted

CPU utilization for five seconds: 98%/94%; one minute: 94%; five minutes: 88%

PID Runtime(uS)     Invoked      uSecs   5Sec   1Min   5Min TTY Process

118  3747800704     3426462       2347  2.13%  2.71%  2.37%   0 IP Input        

126     3060000         175      17485  0.45%  0.03%  0.04% 514 SSH Process     

  22  1275008000     4030571        316  0.22%  0.24%  0.22%   0 ARP Input       

274   310512000      786648        394  0.22%  0.19%  0.18%   0 IP NAT Ager     

...

These are the top processes. The CPU is at 98% but there is no process using more then 3%. This processes usage is the same even when the CPU load is normal.

Any ideas how to troubleshoot this?

Regards.

[Joseph W. Doherty]

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The "missing" CPU is "interrupt" CPU, which generally is devoted to f