STP error

[suthomas1]

Hello,

While connecting a nexus switch to another nexus switch via trunk , the port went into err-disabled mode indicating following error-

%STP-2-BLOCK_BPDUGUARD: Received BPDU on port Ethernet101/1/2 with BPDU Guard enabled. Disabling port

ETHPORT-5-IF_DOWN_ERROR_DISABLED: Interface Ethernet101/1/2 is down (Error disabled. Reason:BPDUGuard).

Can experts here suggest how this can be done properly. what should be the configuration?

One of the switches is a nexus 5K & the other nexus 9k is been linked up to 5k via fex connected on 9k.

Thanks in advance.

[S-Lemming]

Since you are connecting two switches you need to disable BPDU Guard on the interfaces which the switches are connected on. In the interface configuration type the command spanning-tree bpduguard disable.

Hope this helps.

[suthomas1]

Thanks , one of the ports involved is a FET port on a nexus 2k.

Trying to disable bpduguard gives error saying command is not supported as bpdu guard is enabled by default on FET.

Please advice.

[S-Lemming · Accepted solution]

Sorry, I didn't realize you were using a FEX for connectivity. On the FEX BPDU Guard is enabled permanently for the simple reason that it is supposed to be used for host connections only. Best solution would be to connect the switches directly, bypassing the FEX.

There is a possibilty, however not in any way recommended, to enable BPDU Filter on the 5k interfaces connecting to the 2k FEX. Please advise that if doing this the 5k will not be part of the Spanning-Tree topology and this may cause loops in your network! I would not recommend doing this at all.