200-301 Question 221
Single answerA network administrator is troubleshooting a network using the Spanning Tree Protocol (STP). During the process, they observe that a particular port on a switch is in the 'Listening' state. What is the primary purpose of the port in this state?
- A
To forward user traffic across the network
- B
To learn the MAC addresses from incoming frames
- C
To prevent loops by listening to BPDU messages
- D
To block traffic while waiting for the network topology to stabilize
Show answer and explanation
Correct answer: C
Explanation
In the Spanning Tree Protocol (STP), the 'Listening' state is a transitional state where the port processes BPDUs to detect loops and determine the network topology. No user traffic or MAC address learning occurs in this state. This state is crucial for ensuring a loop-free topology before moving the port to the 'Learning' or 'Forwarding' state.
- A. Incorrect.
Incorrect. A port in the 'Listening' state does not forward user traffic. Forwarding occurs in the 'Forwarding' state.
- B. Incorrect.
Incorrect. A port in the 'Listening' state does not learn MAC addresses. This happens in the 'Learning' state.
- C. Correct.
Correct. In the 'Listening' state, the port listens for BPDUs to determine the network topology and detect loops.
- D. Incorrect.
Incorrect. While the port does block traffic in the 'Listening' state, its main function is to listen for BPDUs, not just wait for stabilization.