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352-001 · Question #767
352-001 Question #767: Real Exam Question with Answer & Explanation
The correct answer is A: Fiber Ethernet connectivity with UDLD enabled. Fiber Ethernet with UDLD enabled provides the fastest convergence for unidirectional link failures because UDLD is a Layer 2 protocol specifically designed to detect and respond to unidirectional conditions on fiber optic connections.
Question
Which interconnectivity method offers the fastest convergence in the event of a unidirectional issue between three Layer 2 switches connected together with trunk links?
Options
- AFiber Ethernet connectivity with UDLD enabled
- BCopper Ethernet connectivity with BFD enabled
- CFiber Ethernet connectivity with BFD enabled
- DCopper Ethernet connectivity with UDLD enabled
Explanation
Fiber Ethernet with UDLD enabled provides the fastest convergence for unidirectional link failures because UDLD is a Layer 2 protocol specifically designed to detect and respond to unidirectional conditions on fiber optic connections.
Common mistakes.
- B. BFD (Bidirectional Forwarding Detection) operates at Layer 3 to accelerate routing protocol convergence and does not detect Layer 2 unidirectional trunk link issues; copper is also inherently less prone to unidirectional failures.
- C. BFD is a Layer 3 failure detection mechanism and cannot detect Layer 2 unidirectional conditions that UDLD is specifically designed to address on fiber links.
- D. Copper Ethernet relies on auto-negotiation which typically detects failures bidirectionally, and UDLD's primary benefit targets fiber where independent TX and RX strands make unidirectional failures most common.
Concept tested. UDLD unidirectional fiber link detection on Layer 2 trunks
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