Spanning-Tree Bridge Assurance

Spanning-tree BPDUs are a one way process. Means, a switch can only send the BPDUs for announce itself. But it can’t expect the response of these BPDUs. We can change this behavior by using the Spanning-Tree Bridge Assurance. bridge assurance enables the two-way BPDU communication.

All operational ports will send the BPDUs , including the ports which are in alternate or backup state. So unidirectional or malfunctioning can be detect easily. If return BPDU is receiving then spanning-tree will move the port into BA-inconsistent state. in this state data traffic can’t be send or receive on that port.

By default, Bridge assurance is enable on peer-link. but we can also enable it on other ports.

We should disable the Spanning-Tree Bridge Assurance , If port is connected to end user device.

But we should not disable it in below cases.

1. Bridge assurance should not be disable on peer-link.
2. We are using back-to-back VPC then we should not disable bridge assurance,
3. If ports are connect to other switches then bridge assurance should not be disable on those ports.

If we are using bridege assurance then no need of UDLD

N1# conf t
N1(config)# interface port-channel 15
spanning-tree bridge-assurance

Below is the topology of back to back VPC:

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