Which two OSPF network type combinations can you use in the design of a Phase 3 DMVPN that requires spoke-to-spoke direct traffic? (Choose two.)

Question

Options

• Ahub as point-to-multipoint and spokes as non-broadcast
• Bhub as point-to-multipoint and spokes as point-to-point
• Chub as broadcast and spokes as non-broadcast
• Dhub as point-to-point and spokes as point-to-point

• A
  30% (15)
• B
  58% (29)
• D
  12% (6)

Explanation

Phase 3 DMVPN enables spoke-to-spoke traffic directly after an NHRP redirect from the hub. For OSPF to support this, spokes must receive individual routes to all other spokes (no summarization). Option B (hub as point-to-multipoint, spokes as point-to-point) works because P2MP on the hub advertises a /32 host route per spoke with no DR election, so every spoke gets a specific route to every other spoke. Spokes in P2P mode install those routes and can redirect traffic directly. Option C (hub as broadcast, spokes as non-broadcast) works because the hub becomes the OSPF DR (it can reach all spokes) and distributes LSAs containing all spoke routes; spokes in non-broadcast mode send unicast OSPF updates to the hub DR and learn all spoke prefixes needed for direct routing. Option A fails because P2MP on the hub and non-broadcast on spokes creates a network-type mismatch that prevents proper OSPF adjacency formation. Option D (both hub and spokes as P2P) fails because OSPF P2P only expects a single neighbor per interface, which is incompatible with the multipoint nature of the DMVPN hub.

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