What is Bridge Assurance?

--> Bridge Assurance is one of the STP features that is used to avoid switching loops in your network.

--> When bridge assurance is configured on the switch then BPDUs are sent on all interfaces of the switch, including blocked interfaces like the alternate or backup port.

--> If the interface doesn’t receive a BPDU for a certain time from the neighbor switch then the interface goes into the blocking state.

--> If the interface receives BPDUs again, the interface is unblocked and goes through the normal spanning-tree port states again.

--> Bridge Assurance helps to avoid switching loop because of unidirectional link failures or any other reason.

--> Bridge assurance only works on RPVST and MSTP.

--> Bridge Assurance is supported on both Nexus OS and Cisco IOS.

--> By default Bridge Assurance is enabled globally but not activated on the interfaces.

--> The port must be configured to a spanning tree port type of “network” in order to bridge assurance to work on that port. 

--> Bridge Assurance only works on point to point connections between two switches and both the switches should support Bridge Assurance.

Configuration:

SW(config)# spanning-tree bridge assurance

SW(config)# interface gig x/x

SW(config-if)#spanning-tree portfast network