Receiving Bridge Behavior

The receiving bridge must decide whether or not to accept a proposal from a port.

Upon receiving a proposal for a root port, the receiving bridge:

• Processes the BPDU and computes the new STP topology.

• Synchronizes all of the designated ports if the receiving port is the root port of the new topology.

• Puts all unsynced, designated ports into the blocking state.

• Sends down further “propose” messages.

• Sends back an “agree” message through the root port.

If the receiving bridge receives a proposal for a designated port, the bridge replies with its own BPDU. If the proposal is for an alternate or backup port, the bridge keeps silent.