350-401 Question 339
Single answerAn enterprise network engineer is configuring OSPF in a multi-area environment. The network consists of several areas, including Area 0 (backbone) and Area 1. The engineer needs to ensure that routes from Area 1 are summarized when advertised into Area 0 to reduce the size of the routing table. Which OSPF configuration step achieves this goal?
- A
Configure a summary address on the Area 1 ABR using the 'area range' command.
- B
Use the 'summary-address' command on Area 0 routers.
- C
Enable OSPF route summarization on all routers in Area 1 using the 'auto-summary' command.
- D
Configure the 'default-information originate' command on the Area 0 ABR.
Show answer and explanation
Correct answer: A
Explanation
To summarize routes between OSPF areas, the 'area range' command must be configured on the Area Border Router (ABR) for the area where the summarization is needed. In this scenario, the engineer needs to summarize routes from Area 1 when they are advertised into Area 0. The other options refer to commands that are not applicable or are used for different purposes, such as external route summarization or default route advertisement.
- A. Correct.
Correct. The 'area range' command is used on an ABR to summarize routes from one area before advertising them to another area. This reduces the number of specific routes advertised and minimizes the routing table size in other areas.
- B. Incorrect.
Incorrect. The 'summary-address' command is used for redistributing external routes into OSPF, not for summarizing inter-area routes.
- C. Incorrect.
Incorrect. OSPF does not use the 'auto-summary' command, as it is specific to distance-vector protocols like RIP or EIGRP. OSPF requires manual configuration for summarization.
- D. Incorrect.
Incorrect. The 'default-information originate' command is used to advertise a default route into the OSPF domain, not for summarizing routes between areas.