What does enabling STP Loop Guard do?

Enabling Spanning Tree Protocol (STP) Loop Guard enhances the stability and reliability of a network by providing additional protection against bridge loops that can occur due to BPDU loss. When Loop Guard is enabled, it monitors the ports for the presence of BPDUs (Bridge Protocol Data Units).

If a designated port does not receive any BPDUs from its upstream device for a specified period, it may be susceptible to becoming a loop due to misconfigurations or network issues. Loop Guard prevents this scenario by placing the downstream port in a loop-inconsistent state rather than transitioning it to a forwarding state. This effectively disables the port until BPDUs are detected again, thereby eliminating the risk of creating a network loop.

This behavior contrasts with the other options, which do not accurately reflect the function of Loop Guard. For instance, while some options mention port states or BPDU behaviors, they do not capture the essence of Loop Guard's prevention mechanism against loops resulting from BPDU loss specifically. Thus, recognizing the critical role Loop Guard plays in maintaining network stability makes the selected option the appropriate choice.