200-301 Question 289
Single answerA network engineer is configuring a routing protocol and notices that two routes to the same destination network are being advertised by different protocols. One route is learned via OSPF with a cost of 20, and the other is learned via EIGRP with a composite metric value of 156160. Which route will be installed into the routing table, and why?
- A
The route learned via OSPF, because OSPF has a lower cost metric.
- B
The route learned via EIGRP, because EIGRP's composite metric is more granular and preferred.
- C
The route learned via EIGRP, because EIGRP has a lower administrative distance.
- D
The route learned via OSPF, because OSPF has a higher administrative distance and is preferred in tie-break scenarios.
Show answer and explanation
Correct answer: C
Explanation
When a router learns routes to the same destination network from different routing protocols, it compares their administrative distances. The administrative distance is a measure of trustworthiness, where a lower value is preferred. In this scenario, EIGRP has a default administrative distance of 90, while OSPF has a default administrative distance of 110. Thus, the route learned via EIGRP will be installed into the routing table, regardless of the metric values.
- A. Incorrect.
Incorrect: While OSPF uses cost as its metric, route selection is determined by administrative distance when comparing routes from different protocols.
- B. Incorrect.
Incorrect: The granularity of a protocol's metric does not determine route selection when comparing protocols. Administrative distance is the deciding factor.
- C. Correct.
Correct: EIGRP has a default administrative distance of 90, which is lower than OSPF’s default administrative distance of 110. This makes EIGRP's route the preferred choice, regardless of the metrics.
- D. Incorrect.
Incorrect: OSPF has a higher default administrative distance (110) than EIGRP (90). This means EIGRP is preferred, not OSPF.