If an IGP or MPLS link frequently flaps and the flapping interval is greater than the IGP or MPLS recovery time, BFD detects the link flapping and notifies an upper-layer protocol of the event. As a result, the upper-layer protocol frequently flaps. BFD dampening prevents link flapping detected by BFD from causing the frequent flapping of the upper-layer protocol.
BFD dampening enables the BFD session's next negotiation to be delayed if the number of times that a BFD session flaps reaches a threshold. However, IGP and MPLS negotiation is not affected. Specifically, if a BFD session that is always flapping goes Down, its next negotiation is delayed, reducing the number of times that the BFD session flaps.