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352-001 · Question #281
352-001 Question #281: Real Exam Question with Answer & Explanation
The correct answer is B: IP Event Dampening. IP Event Dampening suppresses a flapping interface from advertising state changes to routing protocols until the link stabilizes, preventing repeated OSPF reconvergences across the MPLS VPN network.
Question
There is an MPLS-enabled link constantly flapping on an MPLS VPN network. Given that the network runs OSPF as the IGP protocol, which design mechanism will stabilize the network and avoid constant reconvergences?
Options
- ABFD
- BIP Event Dampening
- COSPF fast hellos
- Dpartial SPF
Explanation
IP Event Dampening suppresses a flapping interface from advertising state changes to routing protocols until the link stabilizes, preventing repeated OSPF reconvergences across the MPLS VPN network.
Common mistakes.
- A. BFD (Bidirectional Forwarding Detection) is designed to detect link failures faster and notify OSPF sooner, which would cause more frequent reconvergences on a flapping link - the opposite of the desired stabilization.
- C. OSPF fast hellos reduce the dead interval to sub-second values, accelerating failure detection and triggering reconvergences more frequently rather than dampening them, which would worsen instability on a flapping link.
- D. Partial SPF optimizes the speed of OSPF's Shortest Path First calculation for incremental topology changes, but it does not suppress or prevent the reconvergence events triggered by a repeatedly flapping link.
Concept tested. IP Event Dampening to stabilize OSPF on flapping MPLS links
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