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…

Question

Options

• AAdjust the GRE keepalive timers
• BEnable BFD
• CDeploy IPsec dead peer detection
• DAdjust the NHRP timers.

• A
  9% (2)
• B
  73% (16)
• C
  14% (3)
• D
  5% (1)

Explanation

BFD (Bidirectional Forwarding Detection) is a lightweight, protocol-independent hello mechanism specifically designed for sub-second failure detection, operating independently of the routing protocol's own timers - so it detects neighbor loss in milliseconds even when EIGRP timers are locked down.

Why the distractors fail:

• A (GRE keepalives): GRE keepalives detect tunnel failure at the transport layer but are not tied to EIGRP neighbor state and won't trigger EIGRP reconvergence directly or reliably within 3 seconds.
• C (IPsec DPD): Dead Peer Detection checks if an IPsec peer is alive, not the EIGRP routing neighbor - it operates at the security layer and doesn't satisfy the routing-layer detection requirement.
• D (NHRP timers): NHRP manages spoke-to-hub registration and dynamic tunnel resolution in DMVPN; it doesn't monitor EIGRP neighbor adjacency health.

Memory tip: Think of BFD as a "heartbeat monitor" that any protocol (EIGRP, OSPF, BGP) can outsource its neighbor-detection to - whenever the question says "fast failure detection without changing the routing protocol's own timers," BFD is almost always the answer.

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