200-301 Question 219
Single answerA network administrator is troubleshooting a spanning-tree topology. During the analysis, the administrator notices that a switch port is in the 'Blocking' state. Which of the following best describes the role and behavior of this port in the spanning-tree protocol?
- A
The port is an alternate port that prevents loops and only forwards traffic when the root port fails.
- B
The port is a designated port actively forwarding traffic in the spanning-tree topology.
- C
The port is in a learning state, preparing to transition to forwarding by processing MAC addresses.
- D
The port is a root port directly connected to the root bridge and forwarding traffic.
Show answer and explanation
Correct answer: A
Explanation
In the spanning-tree protocol (STP), a port in the 'Blocking' state is not forwarding traffic to prevent loops in the network. This state is typically associated with alternate ports, which are ready to transition to forwarding if the root port fails. Understanding the roles and states of ports in STP is crucial for maintaining a stable and loop-free topology.
- A. Correct.
Correct. A port in the 'Blocking' state is typically an alternate port in the spanning-tree topology, and its role is to prevent loops by not forwarding traffic unless necessary (e.g., if the root port fails).
- B. Incorrect.
Incorrect. A designated port is actively forwarding traffic and does not remain in the 'Blocking' state.
- C. Incorrect.
Incorrect. A port in the 'Learning' state is processing MAC addresses to prepare for forwarding but is not in the 'Blocking' state.
- D. Incorrect.
Incorrect. A root port is the port directly connected to the root bridge, and it is always in the 'Forwarding' state, not 'Blocking.'