A network designer wants to improve a company network design due to multiple network crashes. Which technology would allow for the restore of a network connection without informing the Layer 3…

Question

Options

• ABidirectional Forwarding Detection
• Bautomatic protection switching
• CUDLD
• DEthernet OAM

• A
  6% (3)
• B
  81% (42)
• C
  12% (6)
• D
  2% (1)

Explanation

Automatic Protection Switching (APS) operates at Layer 1/2 and performs failover to a backup path so quickly and transparently that Layer 3 protocols (like OSPF or BGP) never detect a disruption - they simply continue forwarding as if nothing happened. This makes it the ideal solution when the goal is seamless recovery from physical or data-link failures without triggering routing reconvergence.

Why the distractors are wrong:

• A. BFD does the opposite - it rapidly notifies Layer 3 routing protocols (OSPF, BGP, etc.) about failures so they can reconverge faster. It informs Layer 3, not bypasses it.
• C. UDLD detects unidirectional link failures (one-way fiber breaks) and shuts down affected ports, but it has no mechanism to restore connectivity or hide the failure from upper layers.
• D. Ethernet OAM provides fault detection, monitoring, and management for Ethernet links, but it is a management framework, not a protection-switching technology - it reports problems rather than transparently fixing them.

Memory tip: Think of APS as a "silent stunt double" - when the primary path goes down, the backup path steps in so smoothly that Layer 3 never even knows the original actor left the scene.

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