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Community Member

What caused 100% CPU usage after seeing "show process cpu history"?

I received an alert from one of my routers for high CPU utilization. The router responded to ping, so it was still active. I tried to telnet to the router, but the attempt timed out. After about 10-20 minutes, I managed to access the router. I did a 'show process memory' and 'show process cpu'. I did not notice any process high compared to my baseline.  The 'show process cpu history' did vouch that the router experienced high CPU.

Anyone suggest how I go about trying to find out what caused the spike? Monitoring tools, other commands, etc.?


High CPU History.jpg

VIP Super Bronze

Re: What caused 100% CPU usage after seeing "show process cpu hi

Reasons for CPUs spike include traffic that normally is handled via CEF switching all of a sudden gets process switched, bad TTL values which result in the traffic reaching the CPU of the device, an ACL which starts filtering WAY too much traffic, IGP instability resulting in lots of CPU cycles spent on recalculations/convergence. Also, IPSec can cause CPU issues, especially if you're doing software encryption

I would also check your current IOS version running on the box for any kinds of bugIDs, specifically memory issues and buggy processes.



Community Member

Re: What caused 100% CPU usage after seeing "show process cpu hi


Another thing you can do is to setup a SPAN session, which can be configured to mirror all the packets that are sent to the RP, instead of being CEF switched. A guide on how to do that can be found here:

It includes different switch models, etc.

Hope it helps


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