Cisco Certified Network Associate (CCNA) Practice Exam

What happens to a port in STP that is in the blocking state?

1. It forwards data packets.

2. It listens for BPDUs.

3. It forwards BPDUs only.

4. It does not forward any traffic.

The correct answer is: It does not forward any traffic.

The port in the blocking state does not forward any traffic. In the Spanning Tree Protocol (STP), the blocking state is part of the process that prevents loops in the network topology. When a port is in the blocking state, it is effectively disabled for data traffic, meaning it will not forward any data packets generated by devices connected to the network. However, it is important to note that while the port does not forward regular traffic, it still participates in STP processes by listening for Bridge Protocol Data Units (BPDUs). This allows the port to stay updated on the network topology and be ready to transition to a different state if the network changes (for example, if necessary due to a topology change). Thus, while it maintains some level of function by listening to BPDUs, it does not impact the flow of data traffic.