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THREAD and SptBpduRx processes high in CPU

I have got 17 Catalyst switches 5500 CatOS 5.5(9) in the network. They all have two connections to two core switches. However, port 1/2 is alway blocking at the leaf end for all VLANs. One of the core switches is the root for all VLANs.

I started monitoring the devices using SNMPc and found that two of those switches miss one poll every 2 or 3 minutes.

When I log in those switches and type sh cpu proc there are two precesses that are pushing the CPU utilisation of the switch to 60% these processes are THREAD and SptBpduRx my question is what do they indicate and where should I start looking to bring those processes down. When I compared them to the core switch they are up to 15 times higher than those shown in the core switch.

Can anyone give me some ideas as to what the problem might?

Regards,

Arturo.

5 REPLIES
New Member

Re: THREAD and SptBpduRx processes high in CPU

THREAD is the process that actually processes any SNMP request. The snmp process first receives any snmp request and then calls the THREAD process to process the request. The snmp process is invoked by the kernel when the system comes up. THREAD process will be invoked by the snmp process as soon as it receives a SNMP request

So please limit your polling to the cat5000 and let me know if that helps. It could be some rougue station who is polling this time a lot or mis-configuration in your snmp polling.

New Member

Re: THREAD and SptBpduRx processes high in CPU

Thanks for the explanation. It has given me a good point to start.

As a first step I stopped polling one of those switches but still can see the thread very high 30% in utilisation.

Next thing I will do is to attach a sniffer and capture the snmp traffic to that switch to look for that rogue workstation you suggest. I will keep you posted.

regards,

Arturo.

New Member

Re: THREAD and SptBpduRx processes high in CPU

When I connected the sniffer I found that there was another system polling form the switch. When I changed the community string the THREAD process was still high in CPU but also discover that the switch started sending SNMP traps to a device that now does not exist. I cleared that command and the CPU went down, however not as low as I expected. During the weekend the threads process went down, as low as the the other switches, however the SptBpduRx and cdptimer processes are still much higher than in other switches. Do you have any idea why.

Thanks for your help.

Arturo.

New Member

Re: THREAD and SptBpduRx processes high in CPU

how high are you talking about ? Have you enabled portfast on all the user ports, may be there is lot of TCN being received. How many vlans you have ? I am just guessing as you have lot of bpdu traffic.

CPU in a switch is really not that critical for normal operation of the switch (switching packets), so you shouldn't see any user impact.

New Member

Re: THREAD and SptBpduRx processes high in CPU

Hi! Balaji,

The SptBpduRx is 11% avg every 5 mins.

The cdptimer is 10% avg every 5 mins.

Compared to the other 14 switches they are high because even the core switches are running at 0.xx every 5 minutes both processes.

I checked the configuration as well and yes! all ports have portfast enabled apart from the trunk.

I have 8 vlans configured but 2 of them have no user population. Only two of them have most of the users, 600 users in each one of them roughly.

I was looking for infomation on the processes above and found, like you say, that CPU should not affect the switch's performance as it forwards packets in hardware.

I thought high CPU may have been the problem as a couple of users complained about slow network, and both two are attached to that switch.

What are the parameters I should be monitoring in order to measure the performance of the switch.

I am keeping an eye on Backplane util, are there any othters? Do you know of any document on this subject for Catalyst 5500?

Thanks for your help.

Regards,

Arturo.

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