200-301 Question 216
Select 3You are configuring a network with multiple switches running Spanning Tree Protocol (STP). Switch A is elected as the root bridge. On Switch B, the port connected to Switch A is designated as a root port. Which of the following statements are true about the roles and behavior of the ports in this topology?
- A
The root port on Switch B is the port with the lowest path cost to the root bridge.
- B
The root bridge's ports are all designated ports unless it has redundant links.
- C
A blocked port can never become a root port in the event of a topology change.
- D
The secondary root bridge takes over immediately if the primary root bridge fails.
- E
A designated port forwards traffic towards the root bridge and is not blocked.
Show answer and explanation
Correct answers: A, B, E
Explanation
Understanding the roles of various STP port types is critical for ensuring a loop-free Layer 2 topology. The root port on non-root switches is determined based on the lowest path cost to the root bridge. All ports on the root bridge are designated ports unless redundancy leads to blocking. Designated ports forward traffic towards the root bridge, while blocked ports can transition roles during topology changes. Secondary bridges only take over after a new election process.
- A. Correct.
Correct: The root port on any non-root switch is the port with the lowest path cost to reach the root bridge.
- B. Correct.
Correct: All ports on the root bridge are designated ports unless redundant links exist, which may cause some ports to be blocked.
- C. Incorrect.
Incorrect: A blocked port can transition to a root port if the current root port fails and the network recalculates the spanning tree.
- D. Incorrect.
Incorrect: The secondary root bridge does not immediately take over. It will only become the root bridge if a new root bridge election occurs due to the failure of the primary root bridge.
- E. Correct.
Correct: A designated port forwards traffic towards the root bridge and is part of the active STP topology.