How does STP identify the root bridge?

Spanning Tree Protocol (STP) identifies the root bridge using the bridge ID, which is a combination of the bridge priority and the MAC address. During the STP process, each switch in the network participates in an election to determine which switch will become the root bridge. The bridge ID is essential in this election process because it uniquely identifies each switch in the network.

The bridge priority is a configurable value that is a factor in determining the root bridge, with lower values being more favorable. In the event of a tie in priority, the MAC address serves as a tiebreaker, where the switch with the lowest MAC address is chosen as the root bridge. By combining these two elements, STP ensures a consistent and deterministic method for identifying the root bridge across the network. This plays a crucial role in maintaining a loop-free topology in Ethernet networks.