Unidirectional Spanning Tree Protocol Failure Detection

B.

The correct answer to this question is B: loop guard.

The Spanning Tree Protocol (STP) is a protocol that is used to prevent loops in a network topology. It is important to ensure that STP is functioning correctly to prevent network outages and disruptions.

Unidirectional failures in STP can occur when a switch stops receiving BPDUs from its neighbor switch. This can happen if a cable is unplugged or if there is a problem with a switch or port. If the switch continues to forward traffic, it can cause a loop in the network, leading to a network outage.

Loop guard is a mechanism that can be added to a network design to identify unidirectional STP failures through BPDU loss. Loop guard works by monitoring the receipt of BPDUs on a port that is not designated as a root or alternate port. If a port stops receiving BPDUs, loop guard will place the port in the loop-inconsistent state, effectively blocking traffic on that port until the issue is resolved.

Loop guard is an important tool for ensuring the stability and reliability of a network. By detecting unidirectional failures in STP, loop guard can help prevent network outages and disruptions. However, it should be noted that loop guard should be used in conjunction with other mechanisms, such as UDLD, to provide a comprehensive network design that can detect and prevent a range of potential issues.