300-420 Question 4
Select 3An enterprise network is experiencing suboptimal routing between its branch offices and data center due to asymmetric routing. The network uses OSPF as the IGP with multiple areas configured. A design engineer proposes implementing a summarization strategy to fix the issue. What considerations should be taken into account when designing OSPF summarization in this scenario?
- A
OSPF summarization should only be implemented at Area Border Routers (ABRs) or Autonomous System Boundary Routers (ASBRs).
- B
Summarization in OSPF can lead to loss of visibility into specific subnets for troubleshooting.
- C
OSPF supports automatic summarization, so manual summarization is not required in this scenario.
- D
Summarization will reduce the size of the OSPF database and improve convergence time.
- E
OSPF summarization is not recommended when all areas in the network are configured as OSPF Area 0.
Show answer and explanation
Correct answers: A, B, D
Explanation
OSPF summarization is a key design consideration in multi-area OSPF networks to optimize routing and improve scalability. By summarizing routes at ABRs and ASBRs, network designers can reduce the size of the OSPF database, improve convergence time, and enhance network stability. However, this approach comes with the trade-off of losing detailed visibility into specific subnets, which can impact troubleshooting efforts. Summarization must be manually configured and is not applicable in single-area OSPF designs, such as when all areas are configured as Area 0.
- A. Correct.
Correct: OSPF summarization is only performed at ABRs and ASBRs, as these devices separate OSPF areas or external domains, making it the correct location for summarization.
- B. Correct.
Correct: While summarization reduces routing table size, it hides detailed subnet information, which can complicate troubleshooting.
- C. Incorrect.
Incorrect: OSPF does not support automatic summarization; summarization must be manually configured by the network administrator.
- D. Correct.
Correct: Summarization reduces the size of the OSPF database by aggregating routes and improves convergence time by reducing the number of LSAs in the network.
- E. Incorrect.
Incorrect: Summarization is specifically useful in multi-area OSPF designs. It is not applicable if all areas are configured as Area 0, but this does not mean summarization is not recommended in general.