Which selection criterion follows the root cost in STP when deciding the root port?

In the Spanning Tree Protocol (STP), after determining the root bridge based on the Bridge ID, the next step involves identifying the root port for each non-root bridge. The root port is the port on a switch that has the lowest cost path back to the root bridge.

Once the root cost has been established, the selection process moves to the next criterion: the neighbor port ID. This is used to differentiate between ports when two ports have the same cost. The neighbor port ID refers to the port on the neighboring switch that leads to the root bridge. By using the neighbor port ID, STP can determine which port to select as the root port when multiple ports might have the same cost and are connected to the same device.

While options like Port speed and Cost play roles in the evaluation of path selection, they come into play before the neighbor port ID. Specifically, cost is calculated before this step, and a tie situation is resolved with the neighbor port ID when root costs are identical. Similarly, the Bridge ID primarily aids in the initial election of the root bridge rather than influencing the selection of the root port once the root cost is established. This nuanced understanding of the selection process is critical for configuring and troubleshooting network bridges and switches in a