A customer has a DMVPN network with EIGRP as the overlay protocol. EIGRP timers cannot be shortened, yet the customer requires the detection of lost connectivity between neighbors in less than three s

GRE keepalives can detect tunnel failures but are not integrated with EIGRP neighbor state, so they do not directly trigger EIGRP reconvergence within the required timeframe.

BFD (Bidirectional Forwarding Detection) is a lightweight protocol that operates at intervals as low as 50ms, entirely independent of the routing protocol's own hello and hold timers. When BFD is enabled on EIGRP neighbors in a DMVPN topology, it detects adjacency failures in well under three seconds and immediately signals EIGRP to converge, without requiring any changes to EIGRP timer configuration.

IPsec Dead Peer Detection monitors IKE/IPsec peer liveness and does not directly interact with EIGRP neighbor adjacency detection to meet a sub-three-second detection requirement.

NHRP timers govern DMVPN spoke registration and next-hop mapping lifecycles, not EIGRP neighbor adjacency detection timing.