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RSTP Dispute Problem on VPLS Link

I have got two Nexus 7010s connected together by a vPC Peer Link and each has a connection into a VPLS Network. The vPC Peer Link is configured as a port type network and the links to the VPLS as Normal. Also connected to the VPLS is a Catalyst 6500, this doesn't have a specific configuration for its port type. Downstream of the 7Ks is a network of Nexus 5Ks and 2Ks all operating at Layer 2. Downstream of the Catalyst 6500 is a network of Catalyst Switches all operating at Layer 2.

There are two VLANs that spann all this architecture, 2001 and 2002, they flow across all links including the peer link.. We have configured the first 7K as the root of these VLANs and the second 7K as the secondary. The Catalyst 6500 and other switches have no specific configuration.

The problem we have is that for VLAN 2001 the Catalyst 6500 has decided it is root for this VLAN but the first Nexus 7K also says it is root, tjhe surprsing thing is that the VLAN remains unblocked and packets freeley flow across the VPLS. With VLAN 2002 a switch downstream of the 6500 has decided to be root, this has caused the status of this VLAN on the 7K 1 link to the VPLS to be eported as disputed and blocked. This prevents packets from flowing between them.

The two VLANs were already in existence on the 6500 and its downstream switches before it was connected to the VPLS and the configured on the 7Ks.

Can anyone tell me why the status is like this and why things aren't working. Forgive my ignorance, maybe I need to configure something on the 7Ks?

The VPLS supplier has told me that his switches do not paricipate in our spanning tree. His ports are set to perform QinQ between the three devices of 7K 1, 2 and 6500.

I hope someone can help with this as it is driving me mad!



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Cisco Employee

RSTP Dispute Problem on VPLS Link

Hello Paul,

It would be interesting to see if BPDUs are being sent/received on the links connecting the switching claiming to be root.

You can check using show spanning int x/y det.



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