300-410 Question 22
Single answerA network engineer is troubleshooting route redistribution between OSPF and EIGRP on a dual-protocol network. The network engineer notices that EIGRP-learned routes are not being advertised into OSPF. The engineer has verified that the 'redistribute eigrp' command is configured in the OSPF process. What is the most likely cause of the issue?
- A
The OSPF process does not have a default metric defined for redistributed routes.
- B
The 'redistribute eigrp' command is missing the 'subnets' keyword.
- C
EIGRP routes have a higher administrative distance, so they are being suppressed by OSPF.
- D
The OSPF area is configured as a totally stubby area, which does not allow external routes.
Show answer and explanation
Correct answer: B
Explanation
In OSPF, when redistributing routes from another protocol like EIGRP, the 'subnets' keyword must be included to ensure both classful and classless routes are injected into OSPF. Without the 'subnets' keyword, only classful routes will be included, which can lead to missing routes in the OSPF domain. This is a common misconfiguration during route redistribution troubleshooting.
- A. Incorrect.
This is incorrect because in OSPF, if a default metric is not defined for redistributed routes, the system will assign a default value of 20 for external routes. This issue alone would not prevent route redistribution.
- B. Correct.
This is correct. In OSPF, the 'subnets' keyword is required when redistributing routes from protocols like EIGRP to include both classful and classless subnets. Without it, only classful routes will be redistributed, which might not reflect the desired behavior.
- C. Incorrect.
This is incorrect because the administrative distance of a route does not affect route redistribution. Administrative distance is used for route selection within a routing table, not for controlling redistribution.
- D. Incorrect.
This is incorrect because a totally stubby area in OSPF does not block internal routes from being redistributed into OSPF. Instead, it limits the type of external routes injected into the area, which is not relevant to this scenario.