CEF adjacency updates

george_daly · ‎02-12-2007

I recently noticed the CEF switching process on a 6509 was running at about 3% whereas it used to be < 1%.

Looking at the output of 'show ip cef events' there are constant adjacency updates for /32 addresses which are DHCP servers all hanging off a 3550 which is attached to one of the 6509 ports.

We are not using DHCP snooping.

I can't see anything wrong with the trunk between the 6509 and 3550. Logs don't reveal anything of interest.

I'm a bit stuck on where to look next to diagnose this - any suggestions?

Thanks,

George

vmoopeung · ‎02-16-2007

Before you look at the CPU packet-handling architecture and troubleshoot high CPU utilization, you must understand the different ways in which hardware-based forwarding switches and Cisco IOS? Software-based routers use the CPU. The common misconception is that high CPU utilization indicates the depletion of resources on a device and the threat of a crash. A capacity issue is one of the symptoms of high CPU utilization on Cisco IOS routers. However, a capacity issue is almost never a symptom of high CPU utilization with hardware-based forwarding switches.