Port ID (2 bytes) (BPDU)

Protocol: BPDU (Spanning Tree) BPDU PCI

Field: port ID

Length: 2 bytes

Contents: unique bridge port ID.

Each bridge port has a unique identifier (2 bytes long).

The value '0' is not used.

Configuration BPDUs use the port ID as source address.

The first, and most significant, octet is a configurable priority. The second octet is a number assigned by the bridge to the port upon which the configuration message was transmitted.