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intermittent High CPU in 3750/2960 switches

Hi All,

I am facing intermittent high CPU in my LAN network. We have one L3 WS-C3750V2-24TS (c3750-ipbasek9-mz.122-50.SE5)switch and two L2 switches,

WS-C2960S-48TS-S model (c2960s-universalk9-mz.122-55.SE3/c2960s-universalk9-mz.122-55.SE3.bin). The CPU is hitting 90-100% randomly for 1 to 2 hours. No logs are generated about this. Now the CPU seems normal.

sh proc c | ex 0.00

CPU utilization for five seconds: 6%/0%; one minute: 7%; five minutes: 6%

PID Runtime(ms)   Invoked      uSecs   5Sec   1Min   5Min TTY Process

   4   398210517  18807058      21173  0.47%  0.73%  0.72%   0 Check heaps

  92   115442820  48766881       2367  0.15%  0.05%  0.06%   0 hpm counter proc

145   409725440  16255742      25205  0.47%  0.76%  0.77%   0 Power RPS Proces

259         291       128       2273  0.47%  0.36%  0.08%   2 SSH Process

Can anyone suggest the reason for this..?

Thanks in Advance..


Cisco Employee

intermittent High CPU in 3750/2960 switches

Hi Sangeeth,

The CPU becomes too busy when the CPU receives too many packets from the switch hardware or when a system process consumes too much CPU time. When either of these functions uses CPU resources to the detriment of the other, the CPU is too busy

To determine switch CPU utilization

#show processes cpu sorted | ex 0.00%

#show processes cpu history

If the switch is being flooded by a specific packet type, the hardware places that packet type into the appropriate CPU queue and counts it. Enter the show controllers cpu-interface privileged EXEC command to see the packet count per queue.

#show controllers cpu-interface

Each CPU receive queue has a packet-count maximum. When the receive queue maximum is reached, the switch hardware discards packets  destined for the congested queue. The switch counts discarded packets for each queue. Increased discard counts for a particular CPU queue mean heavy usage for that queue

#show platform port-asic stats drop

#show spanning-tree detail | in executing|changes|from - To verify the spanning-tree changes

#show interface | include line|\drops - To see any drops are incrementing on interface level




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Regards, Aru *** Please rate if the post useful ***
Hall of Fame Super Gold

intermittent High CPU in 3750/2960 switches

Upgrade the IOS of your 2960S.  12.2(55)SE3 is not a stable IOS.  Go to 12.2(55)SE8 instead.

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