In a network of LANs connected by bridges, packets are sent from one LAN to…

Answer: The spanning tree algorithm is used to avoid loops in the routing paths between LANs.

Why: Loops in a bridged LAN cause frames (including broadcasts) to be replicated indefinitely, producing broadcast storms and multiple copies of packets. To prevent this, bridges run the spanning tree protocol to create a loop-free topology.

How it works (high-level):

• Elect a root bridge (usually the bridge with the lowest bridge identifier).

• Each bridge selects a single root port that provides the best path to the root bridge.

• For each LAN segment, one port is chosen as the designated port to forward frames toward the root.

• All other ports that would create cycles are put into a blocked state, leaving a single active path between any two LANs.

Result: The active topology is a spanning tree — loop-free — so packets traverse only one path between LANs and broadcast storms are avoided.

Trade-offs and notes:

• Redundant links are disabled to prevent loops, which can reduce immediate redundancy but can be re-enabled if topology changes and the protocol reconverges.

• Spanning tree is not intended to find shortest paths or to directly minimize collisions; its aim is loop prevention.