Wednesday, September 12, 2018

Those of you running Cisco 3750X - what's your CPU utilization?

Hello. We have a campus network with ~750 switches. Some of our switches seem to have really high CPU utilization. Usually, this is our larger stacks, (we have a few 9-stacks), but sometimes it affects medium to small stacks (we've seen it on single switches!).

Our current primary thought is that 802.1x is killing our CPU (we have to re-authenticate hourly - large stacks have lots of 802.1x sessions).... but, show commands don't support that. Also, our worst offender is only a 5 member stack - the CPU utilization is so bad, when SSHing, it feels like we're going over a satellite link, when we have ~55ms RTT. We haven't found a great correlation between any of the affected stacks.

Some hurried research shows IGMP snooping to be a culprit for many people... but we can't turn it off. TCAM utilization is nowhere NEAR 100%. And, according to the switch, the LED process is taking a huge chunk of CPU cycles.

So, what is YOUR CPU utilization? What's typical?



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