What is the configuration state of an STP switch if it does not receive BPDUs?

When a switch is part of a Spanning Tree Protocol (STP) topology and does not receive Bridge Protocol Data Units (BPDUs), it enters the blocking state. This state is crucial for maintaining a loop-free topology in a network. In the blocking state, the switch does not forward frames and only listens for BPDUs.

The rationale behind this behavior is that switches use BPDUs to communicate and learn about the network topology. If a switch does not receive any BPDUs, it infers that it may not have a proper connection to other switches or that it may not be part of the current spanning tree. Thus, to prevent potential network loops— which can occur if the switch begins to forward traffic without knowing its role in the network— it will remain in the blocking state until it receives BPDUs.

In contrast, the other states serve different roles within STP. The listening and learning states are transitional states where the switch processes incoming BPDUs to learn about the network topology, and the forwarding state is where the switch actively forwards frames and participates in the network. Each of these states has a different purpose, but the blocking state specifically addresses the scenario of not receiving BPDUs to prevent loops and maintain network