High CPU on RSM

[daniel.bowen]

I have a Cat5500 with an integrated RSM, performing interVLAN routing for about 20 Vlans (3 of which are populated with about 500 wks on each). The CPU sits at around 10-30% most of the time, but occasionally shoots up to 80-100%. On doing a show proc cpu I find that IP input is at 20-30%. I have three access lists configured on the router, and one of the VLANs is our Internet connection. Can anybody see any reason or give me any tips on how to solve this CPU problem, as sometimes it causes the RSM to freeze and I get multiple throttles on the highly populated interfaces.

Thanks in advance

Daniel,

[glen.grant]

What type of switching are you using ? CEF , ip fast switch etc.. Make sure you are using fast switching of some type whether CEF or ip fast switching . If not small swings in traffic can make big hits on the CPU performance .

[daniel.bowen]

We are using IP Fast Switching on every interface.

Thanks,

[glen.grant]

One other question would be , is your RSM,switch setup for multi layer switching , this would take a big load off your CPU also . To check go to layer 2 side and do a "show mls entry" , you should see many different flows being switched . If it is not I would check the Cisco site on how to set this up on your switch and or if your installed equipment will support this feature .

[ndarukha]

Hi Daniel,

This document describes the troubleshooting steps while working on a high CPU issue with Cisco routers.

http://www.cisco.com/warp/customer/63/highcpu.html

In this document there is a section on "High CPU Utilization due to Processes" which mentions what to look for when the process hogging the CPU is "IP Input"

Also, please go through this document "Understanding Inter-VLAN Routing with a

Route-Switch Module (RSM)" on CCO

http://www.cisco.com/warp/public/473/56.html

There is a section on performance issues under "RSM specific troubleshooting" which goes through the important fields of "show controller c5ip" command. This will help you redistribute load across the two DMA channels in case one channel is overloaded.

Nash

[daniel.bowen]

Excellent document, thanks very much

Daniel,