High CPU utilization on C3700 ???

My 3700 router keeps getting high CPU utilization (average 50 - 60 %). When it reached 80% or higher, most web sites got time-out and we lost internet connection. Bandwidth monitor from TimeWarner showing usage just about 40% (4 Mbs/10 Mbs):

e0: in from Timewarner telecom 10 Mbs e1: out connnected to 4507 with 21 sub interfaces Config has been changed for years. Few access lists run to prevent sub-int talk together.

If you know any reason may lead to CPU high, please let me know. I want to try all solutions befor it gets worse.

Thank you in advance!

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Find out which process is eating CPU.

I can give you more info if you can post the result of the following.

show process cpu | exclude 0.00

- Joe

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Thanks Joe, very useful command I found that CID 33 around 10.5% with IP Input

I also put SolarWin in to monitor all interfaces of the router and noticed that 1 interface that has about 6 computers connected use 1.71 Mbs while the other interface with over 200 employees use only 0.3 Mbs. Do you think we got virus in the vlan connected to high usage bandwidth?


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Virus is always usual suspect.

With 10% IP Input, CPU is high due to interrupts. In other words, packet are being process-switched. 1.7Mbps of 10Mbps interface is not a problem if they are fast-switched or CEF switched. Check packet rate also. Small packets make router very unhappy. Try "show ip interface " to see if you are running fast-switching or cef-switching. There should not be "no ip route-cahce" in interface config.

If you are already running fast-switching, try enabling CEF switching. "ip cef" in glabal command will enable CEF. If CPU is still high with CEF, things get hairy. Things like a long ACL on interface, policy routing, packets TTL gets to 0 .. they are all process switched.

formatting link
should help.

Let me know if you find a smoking gun.

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