On an OSPF network, one router with P2P as the network type is directly connected to another router with P2MP as the network type. If the Hello intervals on the two interfaces are changed to be the…

Question

Options

• ATRUE
• BFALSE
• C
• D

• A
  13% (4)
• B
  77% (23)
• C
  7% (2)
• D
  3% (1)

Explanation

B is correct because matching Hello intervals alone is insufficient to establish a neighbor relationship - OSPF also requires the Dead interval to match, and P2P defaults to a Dead interval of 40s while P2MP defaults to 120s. Since the question only adjusts Hello intervals, the Dead interval mismatch will still prevent adjacency formation.

Even if both timers were corrected, the network type mismatch creates a deeper problem: P2P and P2MP generate structurally different Router LSAs. A P2P interface advertises a transit link (referencing the neighbor's Router ID), while a P2MP interface advertises /32 host stub routes for each neighbor. This asymmetry causes routing inconsistencies in the LSDB even if the two routers somehow reach a FULL state.

Why A is wrong: It assumes Hello interval alignment is the only prerequisite for adjacency - this ignores Dead interval matching and LSA structure differences that break LSDB consistency.

Memory tip: Think of P2P and P2MP as speaking different dialects of OSPF - they broadcast Hellos the same way (both use 224.0.0.5, no DR/BDR), but they "describe the network" in incompatible LSA formats. Syncing timers fixes one word, not the dialect.

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