show processes cpu
Directly on the router, the router showed a 99% CPU utilization on the last minute & five minutes, after reading a very usefull article directly from CISCO documentation, we came with the following paragraph:
Fast switching on the same interface is disabled
If an interface has a lot of secondary addresses or subinterfaces and there is a lot of traffic sourced from the interface and destined for an address on that same interface, then all of those packets are process-switched. In this situation, you should enable ip route-cache same-interface on the interface. When Cisco Express Forwarding switching is used, you do not need to enable Cisco Express Forwarding switching on the same interface separately.
Just like described on the article , we had several secondary networks with high traffic running on the same Fast Ethernet, to be exact 4 secondary networks. During the peak times the processor was going to a 99% utilization and we were having a horrible packet loss of around 12-21%.
By running the command:
ip route-cache same-interface , this problem was completely solved, our 2610 router went from a killer 99% usage to a 14% ... needless to say no more packet loss.
Ref: http://www.felipecruz.com/blog_high-cpu-utilization-ip-input-cisco-router.php
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