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Help with potential loop

Occasional Advisor

Help with potential loop


I have a number of 3400cl and 2650 switches connected with RSTP enabled.  I have a correctly configured root and had no issues for a number of years.  2 days ago I IMC alerted me that some of the switch were uncontactable.

Looking at the spanning-tree the topology count is currently 84,000+ and the Time since last change is 0 or 1 secs.  All of the ports/trunks that STP have bloked in the post now are all in a forwarding state.

This is the case for all the switches and we have made no changes.

I'm guessing I either have a loop somewhere or a hardware failure.  

So far I've check that RSTP is still enabled on the switches and examined the logs but there is nothing to suggest where the problem lies.

Can anyone provide any information to help me find where the issue is? 

Thanks in adavnce.


Occasional Advisor

Re: Help with potential loop

in the core switch
enable spanning-tree root primary
enable spanning-tree root-guard on all ports

in the access switches
enable spanning-tree admin-edge-port in user ports
enable spanning-tree bpdu-protection in user ports