Preventing Layer 2 Loop in Dark Fiber DCI Protocol

B.

The correct answer to this question is B. UDLD.

UDLD (Unidirectional Link Detection) is a protocol used in Cisco data center infrastructure to detect unidirectional links caused by issues such as fiber failures. When a unidirectional link is detected, UDLD can automatically disable the affected port to prevent a Layer 2 loop from occurring.

In a dark fiber Data Center Interconnect (DCI), where a dedicated optical fiber connection is used to connect two data centers, fiber failures can cause unidirectional links that are difficult to detect. This can lead to a Layer 2 loop, which can cause network outages and disrupt data center operations.

By using UDLD, the network can detect these unidirectional links and prevent a Layer 2 loop from occurring. UDLD sends periodic messages on the link to verify that it is bidirectional, and if no response is received from the neighbor device, the port is considered unidirectional and is disabled.

BFD (Bidirectional Forwarding Detection) is a protocol used for fast detection of link failures between two devices, but it does not address unidirectional link issues. MCP (Multichassis EtherChannel Protocol) is a Cisco proprietary protocol used to bundle multiple links into a single logical link, but it does not address the issue of unidirectional links. LLDP (Link Layer Discovery Protocol) is used for discovering and advertising device information on a local network, but it does not address the issue of unidirectional links either.

Therefore, the correct protocol to prevent fiber failures from causing a Layer 2 loop in a dark fiber DCI is UDLD.