High CPU utilization on 2960 switch

[chatrathabhishek]

Hi

I have a 2960 switch connected in my network. It is showing high CPU utilization upto 80-90%. When I checked I found that the below processes are taking the highest utilization. The image in the switch is LAN base. Can someone please advice on why I am having high utilization on the switch for the below processes and how can I reduce it.

14.69% 14.98% 15.00%   0 Hulc LED Process
14.69% 11.49% 13.97%   0 IP Input
29.07% 28.44% 30.06%   0 DHCPD Receive
 

[lenperez]

Hello chatrathabhishek,

• HULC is a process responsible for link status detection. This task is performed after POST is done. The LED process wakes up every 40ms to maintain the LED states. Inside this infinite loop, it will perform the following tasks:
  • Check Link status on every port
  • If the switch supports POE, it checks to see if there is a Power Device (PD) detected
  • Check the status of the transceiver
  • Update Fan status
  • Set Main LED and ports LEDs
  • Update both Power Supplies and RPS
  • Check on system temperature status
• DHCPD Receive, the high cpu here is because of the amount of DHCP requests being sent in by one device.

Do you have impact in your network? What version are you running? Please check if a link is flapping in your switch.

Regards,

[chatrathabhishek]

Thanks for the explanation

There is slowness in the network and we can only find that DHCP requests are taking most of the traffic. We have an alert setup for high CPU utilization, so we get alerts for the switch for high utilization. The version I am running is 12.2(50)SE5. No link flap has been reported.

Thanks & Regards

[Leo Laohoo]

What is the IOS version used?

[chatrathabhishek]

12.2(50)SE5

[Leo Laohoo]

For 2960-series family of switches (excluding 2960X), the most stable IOS is version 12.2(55)SE9.  You can also try 15.0(2)SE4. 

For the record, I've tested and used 12.2(50)SE trains before and there are reasons why I made recommendations about 12.2(55)SE9 and 15.0(2)SE4.