What are the three criteria used for STP root port selection?

The selection of the root port in Spanning Tree Protocol (STP) is pivotal for maintaining a loop-free topology in Ethernet networks. The correct criteria for STP root port selection focuses on the metrics involved in determining the best path to the root bridge.

The first criterion considered is the root cost, which represents the cumulative cost of the path from the switch in question to the root bridge. Each link on the path has an associated cost, and STP sums these to establish the total cost. The lower the root cost, the more favorable the path to the root bridge.

The second criterion is the neighbor bridge ID. This identifies the switch that the local switch is directly connected to on the path to the root bridge. Each switch in the network has a unique bridge ID, which is formed by its priority value and MAC address.

Lastly, the neighbor port ID indicates the specific port on the neighboring bridge through which the connection to the root bridge occurs. This information is crucial for ensuring the appropriate port is utilized in the path to the root bridge.

Understanding these criteria is essential for grasping how STP maintains efficient and loop-free networks by prioritizing paths based on cost and identifying direct connections to the root bridge. The combination of these specific elements ensures that