High processor utilization on Cisco Catalyst 2960

Processor utilization can be related to so many things, but one about I will write is specific. I’ve noticed that ICMP is high, having in mind that switches are in my LAN, connected directly to root bridge and uplinks are Gigabit Ethernet SFP ports, with small amount of traffic. Processor was around 25% and that was not normal from my perspective.

I issued command show processes cpu sorted 5sec and I received following output:

PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process
148 301464294 1688845103 178 25.88% 26.43% 27.96% 0 Hulc LED Process

Hulc LED Process was above normal values. So, what is Hulc LED Process?

This process is responsible for verifying link status detection and can be intensive if you have SFP ports unused. So you have to disable not connected ports (I have done it for all not connected ports, not just SFP) and issued command again. Output was like this:

PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process
148 301464294 1688845103 178 15.49% 16.79% 17.66% 0 Hulc LED Process

So, I decreased CPU consumption for about 10%, which is not insignificantly, having in mind that manufacturer states that normal consumption can be anywhere between 15% – 40% and that if you are not suffering any other performance issue you can leave it as is. In addition to this you can upgrade your switch to 12.2(58)SE2 but not to 15.0 versions, and this is what Cisco officials states to.

I must say that in this case Cisco explanation was sloppily and imprecisely, but still action I performed gave the result.

I hope that you find this tutorial useful.




Dejan Dzodan

Dejan Dzodan

IT professional for more then 15 years, mostly in financial institutions but with experience in ISP and retail. Proven in networking and overall infrastructure projects. Cisco instructor.

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