Connecting interfaces and high CPU utilisation on IOS CAT6K

Unanswered Question
Nov 16th, 2007

We were connecting about 10 interfaces last nigt to other devices (not Cisco Products) as part of a network upgrade and we were doing this on 2 x different CAT 6500 switches running IOS.

CPU utilisation spiked to near 100% every time an interface changed state. This lasted for a few swconds and stabilised to normal usage soon.

Is it normal to see CPU spikes when connecting interfaces? It happens the same way on two different CAT6K switches that are connected to varios remote devices).

Is the fact that LACP is involved relevant (ie: is the answer to the above different for LACP scenarios)?

Image running on both CAT6Ks is 12.218SXF8.

s72033-entservicesk9_wan-mz.122-18.SXF8.bin

I have this problem too.
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JORGE RODRIGUEZ Fri, 11/16/2007 - 14:01

Alphonse, check this link which will give you an idea of why high cpu occurs and under what circumstances, for example if an interface changes state up/down it would depend if that paricular interface is directly connected to an adjacent router and whether interface is particupating in some type of routing protocols, I have seen interfaces for example participating in OSPF and if interface is constantly in a bouncing scenarion it may trigger cpu spike due to OSPF recalculations, this could be just one example and may not be your case, but there are other factors and show commands to help you check the router or switch in spotting the cause of high cpu spikes discribed in bellow link for you to check and make your own judgement..

http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note09186a00804916e0.shtml#check

HTH

Jorge

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