300-420 Question 139
Select 3A network engineer is tasked with redistributing routes between OSPF and EIGRP in a dual-protocol environment. The engineer notices suboptimal routing paths and routing loops occurring after redistribution. Which of the following actions can help prevent these issues?
- A
Use route tags to identify and filter redistributed routes.
- B
Enable automatic summarization on both OSPF and EIGRP.
- C
Redistribute only specific subnets instead of the entire routing table.
- D
Configure route filtering using distribute-lists or prefix-lists.
- E
Increase the administrative distance of redistributed routes in OSPF.
Show answer and explanation
Correct answers: A, C, D
Explanation
Redistribution between routing protocols like OSPF and EIGRP can lead to issues such as routing loops and suboptimal paths if not handled carefully. Using route tags, redistributing specific subnets, and applying route filtering are effective ways to control route propagation and prevent these problems. Automatic summarization and administrative distance adjustments may not directly address the root causes of loops or suboptimal routing in this case.
- A. Correct.
Using route tags can help track redistributed routes and prevent loops by filtering them out when they re-enter the original routing domain.
- B. Incorrect.
Enabling automatic summarization is not recommended in this scenario, as it can lead to incorrect route aggregation and exacerbate suboptimal routing.
- C. Correct.
Redistributing only specific subnets ensures that unnecessary or overlapping routes are not advertised, reducing complexity and avoiding loops.
- D. Correct.
Route filtering with distribute-lists or prefix-lists can prevent unwanted or problematic routes from being redistributed, helping maintain routing stability.
- E. Incorrect.
Increasing the administrative distance of redistributed routes does not directly prevent loops or suboptimal paths; it merely influences route preference in specific scenarios.