How is the neighbor bridge's priority determined in STP?

In Spanning Tree Protocol (STP), the bridge priority is a significant factor in determining which switch becomes the root bridge in the network topology. The priority value of a bridge is a user-configurable value, ranging from 0 to 65535, with the default being 32768. When a switch is participating in STP, it combines this priority value with its MAC address to create a unique Bridge ID.

When STP evaluates which bridge should be the root, it first looks at the priority. If two switches have the same priority, the one with the lower MAC address is chosen as the root bridge. Therefore, the correct method for determining the neighbor bridge’s priority in STP is through its assigned ID, which comprises the configurable bridge priority combined with the MAC address.

Other options, such as MAC address or port speed, do not play a role in establishing the bridge priority on their own. The STP cost is related to the assessment of the best path to the root bridge but does not determine the bridge's priority; it instead focuses on the cost of the path for traffic forwarding decisions. Hence, the assigned ID, specifically the bridge priority, is crucial in the STP process.