What are Bridge Protocol Data Units?

Bridge Protocol Data Units (BPDU) are network messages used by switches to share Spanning Tree Protocol (STP) information. These packets help prevent loops by identifying redundant links in a network. IEEE 802.1D defines BPDU functionality within STP for network stability. BPDUs contain bridge ID, port roles, and timers for topology changes. Managed switches use BPDU messages to elect a root bridge and calculate best paths.

Types of BPDU and Their Functions:

1. BPDU Filter: This feature prevents a switch port from sending or receiving BPDU messages. It is used on edge ports to prevent unintended topology changes and is often applied to ports connected to end devices like HMIs or PLCs.
2. BPDU Guard: If a BPDU is received on a port with BPDU Guard enabled, the switch automatically disables the port. This helps prevent unauthorized devices from participating in STP, ensuring stability.
3. ROOT Guard: This prevents a port from becoming the root bridge. If a superior BPDU is received on a Root Guard-enabled port, it is blocked to maintain the current root bridge. This is useful when controlling STP hierarchy in a managed network.

Content created by Mike Day