200-301 Question 215
Single answerIn a network running the Spanning Tree Protocol (STP), you are reviewing the topology and observe the following: Switch A is identified as the root bridge, and on Switch B, the interface GigabitEthernet0/1 is designated as the root port. Which of the following statements is true about the STP roles and port selection in this scenario?
- A
GigabitEthernet0/1 on Switch B has the lowest cost path to the root bridge.
- B
Switch A was manually configured as the secondary bridge.
- C
Switch B's root port is determined based on the highest port priority.
- D
A secondary root bridge is automatically configured when a root port is selected.
Show answer and explanation
Correct answer: A
Explanation
In STP, the root port is the port on a non-root switch that provides the lowest cost path to the root bridge. The root bridge is determined through the STP election process based on the lowest bridge ID. The concept of a 'secondary root bridge' is unrelated to this scenario and is typically used for redundancy in network design. Port priority or other metrics only come into play when there is a tie in path cost.
- A. Correct.
Correct: The root port on a switch is the port with the lowest cost path to the root bridge. This is a fundamental concept in STP for determining the spanning tree topology.
- B. Incorrect.
Incorrect: The term 'secondary root bridge' does not apply in this context, and there is no indication in the scenario that Switch A was manually configured as anything other than the root bridge.
- C. Incorrect.
Incorrect: The root port is not selected based on the highest port priority; it is chosen based on the lowest path cost to the root bridge. If costs are equal, other factors like port ID are considered.
- D. Incorrect.
Incorrect: A secondary root bridge is not automatically configured when a root port is selected. The concept of a secondary root bridge refers to redundancy in STP and is not tied to port selection.