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CPU usage high on 6500 with Sup 720

Unanswered Question
Mar 9th, 2009
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Dear Friends,

A 6500 switch with Sup 720 (IOS Ver: 12.2(33) SXH3 occassionally reports high CPU usage. However, the average CPU usage remains low.

Do you suggest any diagnostics that can be run for this. Enclosed are the show proc cpu and show proc cpu history output.

Please let me know if you need the current config of the switch. The switch is a campus distribution switch having around 75 vlans (30 active), OSPF, SNMP, Netflow (for a couple of vlans).

Thanks a lot


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Giuseppe Larosa Tue, 03/10/2009 - 00:33
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Hello Gautam,

I would use sh proc cpu sorted 1 min to have listed the processes that have used the most CPU.

then you could consult TAC case collection under the support page

Hope to help


Kerem Gursu Tue, 03/10/2009 - 00:43
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Hi Guatam,

According to your output , especially your 1 hour graph show periodic spikes. CPU reaches to a peak value , followed by a fall down. This has happened periodically , which makes me think of a periodic activity like a Network Management Server polling some values via SNMP. But I totally agree with Guislar , show proc cpu sorted will help a lot.

Hope to help,


jorge.calvo Tue, 03/10/2009 - 16:52
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show proc cpu sorted will be the most valuable command when you detect the CPU is in a peak. Then, check if process 'Port manager per' is on the top of the list. From time to time, that process overload that particular supervisor model.

Following checks would also help:

1. Number of routes and memory they are consuming.

2. Possible span ports with too much traffic, specially when traffic from many vlans is being spanned.

3. Netflow statistics. For example using command 'sh ip cache flow | i K'


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