In Spanning Tree Protocol (STP), which Bridge ID value is used to elect the root bridge?

In Spanning Tree Protocol (STP), which Bridge ID value is used to elect the root bridge?

• A. Highest Bridge ID
• B. Lowest Bridge ID
• C. Smallest MAC Address
• D. Random Bridge ID

Answer: (B)

STP decides which switch becomes the root by comparing Bridge IDs. Each bridge has a Bridge ID that combines a configurable priority value with the switch’s MAC address. The switch with the lowest Bridge ID is elected as the root. If two bridges share the same priority, the tie is broken by the lowest MAC address. So, the root is chosen based on the lowest Bridge ID, not by the highest ID, nor by the MAC alone, nor randomly.

STP decides which switch becomes the root by comparing Bridge IDs. Each bridge has a Bridge ID that combines a configurable priority value with the switch’s MAC address. The switch with the lowest Bridge ID is elected as the root. If two bridges share the same priority, the tie is broken by the lowest MAC address. So, the root is chosen based on the lowest Bridge ID, not by the highest ID, nor by the MAC alone, nor randomly.