Designing Cisco Data Center Infrastructure (DCID) — Question 39

Which protocol prevents fiber failures from causing a Layer 2 loop in a dark fiber DCI?

Answer options

• A. BFD
• B. UDLD
• C. MCP
• D. LLDP

Correct answer: B

Explanation

The correct answer is UDLD (Unidirectional Link Detection), which is specifically designed to detect and prevent unidirectional links, thus avoiding Layer 2 loops that can arise from fiber failures. BFD (Bidirectional Forwarding Detection) is used for detecting faults in the forwarding path, MCP (Multi-Chassis Link Aggregation) is for link aggregation, and LLDP (Link Layer Discovery Protocol) is for network device discovery, none of which directly prevent Layer 2 loops caused by fiber failures.