Full form: Bridge Protocol Data Unit
Also known as: Bridge Protocol Data Unit
Quick Definition
The STP control frames that switches exchange to elect the Root Bridge and maintain the spanning tree.
BPDUs are the STP hello messages that switches send to share topology information. Configuration BPDUs originate from the Root Bridge and are relayed by all switches. They contain the Bridge ID, Root Bridge ID, path cost, port ID, and timer values. The Root Bridge sends BPDUs every 2 seconds (Hello Timer). BPDUs are used to detect topology changes and trigger reconvergence.
If a port stops receiving BPDUs (MaxAge timer expires — default 20 seconds), STP assumes the Root Bridge is unreachable and begins reconvergence. BPDU Guard shuts down a port if it unexpectedly receives a BPDU — protecting PortFast-enabled access ports.
A Layer 2 loop-prevention protocol that blocks redundant paths in a switched network.
An STP feature that bypasses the Listening and Learning states on access ports, putting them immediately into Forwarding.
Shuts down a PortFast-enabled port if it receives a BPDU, protecting the spanning tree.
BPDUs are the STP hello messages that switches send to share topology information. Configuration BPDUs originate from the Root Bridge and are relayed by all switches. They contain the Bridge ID, Root Bridge ID, path cost, port ID, and timer values. The Root Bridge sends BPDUs every 2 seconds (Hello Timer). BPDUs are used to detect topology changes and trigger reconvergence.
If a port stops receiving BPDUs (MaxAge timer expires — default 20 seconds), STP assumes the Root Bridge is unreachable and begins reconvergence. BPDU Guard shuts down a port if it unexpectedly receives a BPDU — protecting PortFast-enabled access ports.
BPDU falls under the Spanning Tree domain of the 200-301 exam. Understanding it in context with related terms like stp and portfast is essential for answering scenario-based questions correctly.