350-401 Question 147
Select 2A network engineer is tasked with configuring OSPFv2 in a multi-area environment where Area 0 serves as the backbone and Areas 1 and 2 are connected to it. The engineer needs to ensure that routing updates are summarized at the Area Border Router (ABR) between Area 0 and Area 1 to reduce the size of the routing table in Area 0. Additionally, the engineer must ensure that OSPF does not form adjacencies on interfaces connected to a LAN segment with no other OSPF routers. Which configurations should the engineer implement?
- A
Configure the ABR to summarize area routes using the 'area 1 range' command.
- B
Set the OSPF network type to 'point-to-point' on all interfaces in Area 1.
- C
Use the 'passive-interface' command on the interfaces connected to the LAN segment with no OSPF neighbors.
- D
Enable default route advertisement into Area 1 using 'default-information originate' on the ABR.
- E
Apply a distribute list to filter Type 1 LSAs between Area 1 and Area 0.
Show answer and explanation
Correct answers: A, C
Explanation
In this scenario, the engineer must reduce routing table size in Area 0 and avoid forming unnecessary adjacencies. Summarization using the 'area range' command on the ABR helps achieve the first objective by aggregating routes before advertising them. The 'passive-interface' command addresses the second objective by preventing OSPF from forming adjacencies on interfaces where no OSPF neighbors exist. Other options do not align with the requirements or are not applicable for the described scenario.
- A. Correct.
Correct: The 'area 1 range' command allows the ABR to summarize routes from Area 1 into Area 0, reducing the size of the routing table in Area 0.
- B. Incorrect.
Incorrect: Setting the OSPF network type to 'point-to-point' is not required for this scenario and is only relevant if the network topology requires it for adjacency formation.
- C. Correct.
Correct: The 'passive-interface' command ensures that OSPF does not attempt to form adjacencies on interfaces connected to LAN segments with no OSPF neighbors, reducing unnecessary overhead.
- D. Incorrect.
Incorrect: Default route advertisement is unrelated to the requirements of this scenario, as the task focuses on summarization and avoiding unnecessary adjacencies.
- E. Incorrect.
Incorrect: A distribute list is not used to filter LSAs between areas in OSPF. OSPF uses summarization and area boundary rules for controlling route distribution.