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CAT 6500 - Two Core Switches - Both Showing HIGH CPU UTILIZATION

Unanswered Question
Jan 29th, 2007
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Two Core CAT 6500 switches running CatOS:


The CPU Utilization of two CAT 6500 CORE switches are constantly showing over 90% CPU Utilization. The main CPU consumer is always SptBpduRx proces on both CAT 6500.

The customer is not having any impact whatsover in terms of network performance and hence I am ruling out the possibilty of any Spanning Tree Loop. He has had this situtaion for a long time.

I seem to recall that if some sort of Spanning Tree Trace is set on CatOS that this could happen, but I am unable to find any details on this tracing.

Any suggestions on why the CPU utilization is so high, especially the SptBpduRX process and yet there is no impact to any user whatsoever in terms of network performance or connectivity.

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Overall Rating: 3 (2 ratings)
glen.grant Mon, 01/29/2007 - 19:22
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You need to look at how it is configured . How many vlans are defined ? Does it have a lot of trunk links ? If so are all unneeded vlans "manually" pruned (not allowed) off all trunk links ? If you do not prune all unneded vlans off your trunks the switch has to keep a instance of spanning tree for all those vlans . That is definitly way too . I'll guarantee it is haveing some effect on customer traffic if its that high . Start checking around , see if the roots for all spanning trees are where they are supposed to be and blocked ports are where you think they should be . Make sure all user ports have portfast turned on if it isn't this causes constant churn of the spanning tree because TCN's are constantly going on and fast aging the cam tables .

astanislaus Mon, 01/29/2007 - 22:32
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As I said in my problem description first, it is the SptBpduRX that takes 74% of the 90% CPU utililization.

vijayasankar Mon, 01/29/2007 - 22:43
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Thanks for the update.

Can you share Any diagnostics captures that you have gathered from those switches.

(Commands like "show spanning-tree vlan x details", show logging etc)

If possible can you provide a network diagram too?

What is the STP protocol that you are running?

802.1d,802.1w or 802.1s?

Kindly revert back to as much information as possible.



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