How does Spanning Tree Protocol (STP) prevent forwarding loops at OSI Layer 2?

STP prevents Layer 2 forwarding loops by strategically blocking redundant ports on switches. When multiple paths exist between network segments, STP calculates a loop-free logical topology and transitions redundant ports into a blocking state. In this state, the port does not forward user data, preventing frames from endlessly circulating the network. TTL (Time To Live) is a Layer 3 mechanism used by IP to prevent routing loops, not Layer 2 forwarding loops. MAC address forwarding is the fundamental process switches use to send frames to their destination, not a loop prevention mechanism. Collision avoidance is a Layer 1/2 mechanism primarily associated with half-duplex Ethernet (like older hubs) to manage access to a shared medium, not to prevent forwarding loops in a switched environment.