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…

Question

Options

• AIP Event Dampening
• BOSPF fast hellos
• CIP SLA
• DPartial SPF

• A
  79% (15)
• B
  11% (2)
• C
  5% (1)
• D
  5% (1)

Explanation

IP Event Dampening suppresses a flapping interface by exponentially backing off its state advertisements - when a link flaps repeatedly, the router holds the interface in a dampened (down) state rather than advertising each flap, preventing OSPF from triggering constant SPF recalculations and keeping the MPLS VPN network stable.

Why the distractors are wrong:

• B. OSPF Fast Hellos - These speed up failure detection (sub-second), which actually worsens flapping by making OSPF react faster to each state change, driving more frequent reconvergence.
• C. IP SLA - A proactive monitoring/testing tool used to track reachability or performance thresholds; it detects problems but has no mechanism to suppress or dampen flapping interfaces.
• D. Partial SPF - An OSPF optimization that limits SPF calculations to affected nodes (rather than full topology recalc), which reduces CPU load during convergence but does nothing to prevent repeated reconvergence caused by a flapping link.

Memory tip: Think of dampening like a "three strikes" penalty - a link that keeps going up/down gets benched (suppressed) until it proves it can stay stable, similar to BGP route dampening. If you know BGP route dampening, IP Event Dampening is the same concept applied to physical/logical interfaces at Layer 3.

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