Which protocol prevents switching loops in a LAN by creating a loop-free topology?

• A. Dynamic Routing Protocol
• B. Link Aggregation Control Protocol
• C. Spanning Tree Protocol
• D. DHCP

Answer: (C)

Switching loops happen when a LAN has redundant paths, causing frames to loop and create broadcast storms. Spanning Tree Protocol prevents this by building a loop-free topology. It does this by exchanging bridge protocol data units to elect a root bridge, compute the best path costs, and assign roles to ports. Redundant connections are put into a blocking state so only one active path exists between any two devices, which stops loops while preserving a backup path if the primary link fails. If the network changes, STP recalculates and can unblock a previously blocked port to restore redundancy without reintroducing loops. That combination of loop elimination and dynamic reconfiguration is why this protocol is used for preventing switching loops.

Dynamic routing protocols operate at Layer 3 and won’t prevent Layer 2 loops. DHCP assigns IP addresses, not topology. Link Aggregation Control Protocol combines multiple links for higher throughput, but by itself doesn’t prevent loops.