300-320 · Question #186
Refer to the exhibit. Which Layer 2 feature detects a link failure between the switch and router B that decreases OSPF reconvergence to approximately 50 milliseconds?
The correct answer is A. BFD. Bidirectional Forwarding Detection (BFD) is a lightweight, protocol-independent hello mechanism designed to rapidly detect link or path failures between two adjacent devices. It operates in milliseconds (configurable down to ~50ms) and notifies routing protocols like OSPF of…
Question
Refer to the exhibit. Which Layer 2 feature detects a link failure between the switch and router B that decreases OSPF reconvergence to approximately 50 milliseconds?
Exhibits
Options
- ABFD
- BUDLD
- CRSTP
- DPVST+
How the community answered
(66 responses)- A70% (46)
- B9% (6)
- C5% (3)
- D17% (11)
Explanation
Bidirectional Forwarding Detection (BFD) is a lightweight, protocol-independent hello mechanism designed to rapidly detect link or path failures between two adjacent devices. It operates in milliseconds (configurable down to ~50ms) and notifies routing protocols like OSPF of the failure far faster than OSPF's own hello/dead timers. UDLD detects unidirectional link conditions but does not accelerate OSPF reconvergence. RSTP and PVST+ are spanning-tree variants that operate at Layer 2 for loop prevention, not for accelerating Layer 3 routing protocol convergence.
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