Bridge ID (8 bytes) (BPDU)

Protocol: BPDU (Spanning Tree) BPDU PCI

Field: bridge ID

Length: 8 bytes

Contents: unique bridge ID.

A bridge ID is built up (a) by the MAC address of that bridge port with the lowest port ID and (b) by the bridge's priority value. Active bridge use these bridge IDs to determine the most 'cheapest' transmission path to the root bridge; ports with less effective transmission paths to the root bridge are set to stand-by mode.

The bridge ID identifies the bridge transmitting the current configuration message.