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Community Member

Cisco 6509 kernel CPU spike

Hello all,

I have a 6509 that the CPU usage spikes on every 15 seconds or so. The kernel process goes up to nearly 100% then drops back down to it's baseline 20%. The switch is currently only servicing 6 x 4900M switches, 2 blade switches and 2 san switches.

The traffic flow through the switch is well below capacity, and I cannot see any misconfigurations on the device. Spanning tree, VTP, etherchannel and all other configuration looks to be working ok. Nothing is generated in the logs, no flapping interfaces, etc.

The only misconfiguration I can see is in sh ver:

'Patching is not available since the system is not running from an installed image. To install please use the "install file" command.'

I think this is due to the 'install bind sup-bootflash:/sys' command not being applied as the image already exists and is booting from the sup-bootflash. I doubt this would cause the kind of CPU spike I am seeing, though..

I have already been through the 6500 guide linked below for diagnosing this problem and have found nothing relevant.

Can anyone give me a pointer or 2 on where to go next?

Please let me know if you need any further information or output from the device.

Thanks in advance.

Community Member

Re: Cisco 6509 kernel CPU spike

Forgot to mention:


5 2 Supervisor Engine 720 (Hot) WS-SUP720-3B

6 2 Supervisor Engine 720 (Active) WS-SUP720-3B

Community Member

Re: Cisco 6509 kernel CPU spike

I had the similar issue when running 12.2(18)SXF in modular IOS.

Opened a tac case, with no success (switch crashed for good when getting sh tech), then changed to monolithic IOS. Everything running well since then.

If you don't have a particular reason for running modular, consider monolithic.

In my view, the code is waaay more stable, more feature support, and Cisco is working on ISSU for 6500, so the downtime due to upgrades is soon to be none.

My .02$

Community Member

Re: Cisco 6509 kernel CPU spike

Thanks, I shall look in to that.

ISSU is one of the main attractions of the modular image. Do you mean it will soon be available in the monolithic images?

Just out of curiosity, which IOS version are you currently running?

Thanks again,


Community Member

Re: Cisco 6509 kernel CPU spike


after 12.2.33SXI eFSU is supported.


perhaps it will suit your needs.

This happened a while ago for a client and I've put version 12.2.SXF11 on it


Re: Cisco 6509 kernel CPU spike

As SXF code is near (or maybe even has passed) EOL you might consider going to SXI2 code.

In the future only modular code will be supported on Cat6500.


Community Member

Re: Cisco 6509 kernel CPU spike

get the output for

sh mls cef summary

sh mls cef maximum-routes

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