352-001 Question #622: Real Exam Question with Answer & Explanation

The correct answer is A: IP Event Dampening. IP Event Dampening suppresses the propagation of excessive interface state changes to routing protocols using a penalty-based mechanism, preventing interface flapping from destabilizing the routing table. It is the dedicated Cisco IOS feature designed specifically for this purpos

Question

Which solution suppress the effect of excessive interface flapping events on routing protocols?

Options

AIP Event Dampening
BSPF Backoff
CCarrier Delay
DBFD

Explanation

IP Event Dampening suppresses the propagation of excessive interface state changes to routing protocols using a penalty-based mechanism, preventing interface flapping from destabilizing the routing table. It is the dedicated Cisco IOS feature designed specifically for this purpose.

Common mistakes.

B. SPF Backoff introduces incremental delays between successive SPF recalculations within link-state routing protocols like OSPF or IS-IS to reduce CPU load during instability, but it does not suppress the initial reporting of interface state changes to the routing process.
C. Carrier Delay adds a timer that defers reporting a carrier-down event to the routing process, which can absorb very brief transient outages, but it is not designed to track cumulative flapping events or apply exponential decay suppression like IP Event Dampening.
D. BFD (Bidirectional Forwarding Detection) is a sub-second failure detection protocol that accelerates the speed at which routing protocols learn of a forwarding path failure; it increases the sensitivity to link events rather than suppressing them.

Concept tested. IP Event Dampening suppression of interface flapping

Reference. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/interface/configuration/xe-16/ir-xe-16-book/ir-event-dmpng.html

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