200-301 Question 220
Single answerA network engineer is troubleshooting a Spanning Tree Protocol (STP) issue in a network. One of the switches has a port in the 'Blocking' state. What is the primary role of a port in the 'Blocking' state?
- A
To forward user traffic and act as a designated port
- B
To prevent loops by not forwarding user traffic
- C
To learn MAC addresses and participate in the forwarding process
- D
To transition immediately into the forwarding state when a topology change occurs
Show answer and explanation
Correct answer: B
Explanation
In STP, a port in the 'Blocking' state plays a crucial role in preventing loops in the network. It does not forward user traffic or learn MAC addresses but instead listens for BPDU packets to determine the network topology. This ensures that only the necessary paths are active, while redundant paths remain in the 'Blocking' state to provide fault tolerance. Understanding port states is key to designing and troubleshooting STP in a network.
- A. Incorrect.
Incorrect. A port in the 'Blocking' state does not forward traffic or act as a designated port. This is the role of a port in the 'Forwarding' state.
- B. Correct.
Correct. A port in the 'Blocking' state is specifically designed to prevent loops by not forwarding user traffic. It listens for BPDU frames to maintain the STP topology.
- C. Incorrect.
Incorrect. Ports in the 'Blocking' state do not learn MAC addresses or participate in traffic forwarding. Only ports in the 'Learning' or 'Forwarding' states do this.
- D. Incorrect.
Incorrect. Ports in the 'Blocking' state do not transition immediately to the 'Forwarding' state. They must first go through the 'Listening' and 'Learning' states as part of the STP process.