What is the correct syntax to enable Loop Guard on an interface?

The correct syntax to enable Loop Guard on an interface is "spanning-tree guard loop." This command is used in the context of Spanning Tree Protocol (STP) within Cisco networking equipment. Loop Guard is a significant feature designed to prevent bridging loops in the network by ensuring that a port remains in a loop-inconsistent state if it detects that the designated bridge on the segment has lost its connectivity or is not transmitting BPDU (Bridge Protocol Data Unit) messages.

When Loop Guard is enabled on an interface, it helps maintain network stability by placing the port in a blocking state rather than allowing it to mistakenly transition to a forwarding state when no BPDUs are received. This prevention is crucial because if a switch erroneously transitions to a forwarding state without a valid connection to the root bridge, it can create a loop, leading to broadcast storms and network outages.

Other options provided do not represent the correct command syntax used in Cisco's IOS for enabling Loop Guard, often leading to misunderstanding regarding the correct configuration needed for the desired network results. Understanding the right command is essential for network engineers to troubleshoot and configure STP effectively in enterprise networks.