What happens when all switches in the STP domain share the same bridge priority and MAC address?

When all switches in the Spanning Tree Protocol (STP) domain have the same bridge priority and MAC address, the selection process for the root bridge must rely on additional criteria. The bridge priority is the first factor used in determining the root bridge, and if there is a tie, the MAC address serves as the subsequent deciding factor. Because all switches in this scenario have identical bridge priorities, STP cannot designate a root bridge based solely on priority.

Instead, the protocol moves on to its next level of resolution, which is to randomly select a root bridge among these switches. This is done to break the tie, ensuring that a single switch is eventually chosen to manage the spanning tree. This random selection methodology helps maintain network stability by preventing multiple devices from being classified as the root bridge simultaneously, thus reinforcing the importance of unique configurations for effective STP functionality.