300-320 Question #647: Real Exam Question with Answer & Explanation

The correct answer is A: OSPF stub areas such as stubby or totally stubby, when used at the spokes sites in a dual-hub. In a dual-hub DMVPN topology, OSPF stub area behavior has important implications. Option A is correct: stubby (stub) areas at spoke sites in dual-hub topologies can cause suboptimal routing because spokes rely on a default route injected by the ABR hub; if traffic must reach the

Question

Which statements about OSPF stub areas are true? (Choose two.)

Options

AOSPF stub areas such as stubby or totally stubby, when used at the spokes sites in a dual-hub
BOSPF stub areas such as stubby or totally stubby, when used at the spoke's sites in dual-hub
COSPF stub areas such as totally stubby, when used at the spoke's sites in dual-hub topology,
DOSPF stub areas such as totally stubby, when used at the spoke's sites in dual-hub topology,

Explanation

In a dual-hub DMVPN topology, OSPF stub area behavior has important implications. Option A is correct: stubby (stub) areas at spoke sites in dual-hub topologies can cause suboptimal routing because spokes rely on a default route injected by the ABR hub; if traffic must reach the second hub or its connected networks, the default route may not provide the most efficient path. Option C is correct: totally stubby areas at spoke sites in dual-hub topologies can cause a connectivity failure if the primary hub (ABR) goes down, because totally stubby areas block both external (Type 5) and inter-area (Type 3) LSAs - the spoke has no routing information to reach the second hub, leaving it dependent solely on the default route from the failed hub. Options B and D (the truncated alternatives) represent incorrect or less accurate descriptions of these behaviors.

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