[c-nsp] 7206VXR Big CPU Increase After 12.4 Upgrade

[Justin M. Streiner]

On Tue, 30 Jan 2007, Mark Taylor wrote:

> This is looking very much like cpu could potentially increase more quickly
> than traffic. The jump in cpu between images is beginning to concern me a
> little. Has anybody else experienced this? Is it normal?

I can't speak specifically to the resource footprint of IOS 12.4, but a 
few things you should look at would be:

1. your logs - is anything interesting being logged that could yield clues 
to your increased CPU utilization?  You may need to turn the logging 
severity level down to 'debugging' if it isn't there already.  If you 
don't do so, you probably want to enable logging of OSPF adjacency and BGP 
neighbor changes.  Flapping here could indicate a lower-level problem like 
an unstable interface, but the flapping can certainly tear up some CPU 
cycles...
2. Does a 'show proc cpu' show one or two specific processes chewing up 
inordinate amounts of CPU time?  If you see lots of time being dedicated 
to the IP Input process, I'd double-check that CEF is enabled  everywhere 
that it should be.  'show proc cpu hist' may also reveal some interesting 
information.
3. If you're running flow switching, is there anything in the flow cache 
that indicates traffic hitting the router that could jack up the CPU?
4. Look at 'show mem sum' to see if perhaps you're running into a memor 
leak or something?  If a router gets very low on memory, it may try to 
cannibalize some processes (moost notably CEF) to conserve memory.
5. Did the upgrade to 12.4 inadvertantly enable something in your config 
that you didn't want, or disable something you did want?

This isn't everything, but it should be enough to get you started.

jms