200-301 Question 309
Single answerA network engineer is configuring routing protocols on a network with multiple paths between routers. The engineer notices that traffic is not taking the expected shortest path despite all links being operational. Upon further investigation, it is found that the routing protocol metric is influencing path selection. Which of the following statements accurately explains why the shortest path might not be chosen?
- A
The routing protocol uses bandwidth as its metric, and the path with the lowest bandwidth is favored.
- B
The routing protocol uses a composite metric that considers bandwidth and delay, and the chosen path has a lower overall metric.
- C
The routing protocol prefers the path with the least number of hops, regardless of other metrics.
- D
The routing protocol uses administrative distance, not metrics, to choose the shortest path.
Show answer and explanation
Correct answer: B
Explanation
Routing protocol metrics determine the path selection within a specific routing protocol. Routing protocols like EIGRP use composite metrics based on bandwidth, delay, and other factors, which can result in a longer physical path being selected if its overall metric is lower. Understanding the specific metric calculation for a given protocol is essential to predict path selection behavior.
- A. Incorrect.
Incorrect: If the routing protocol uses bandwidth as its metric, it would favor the path with the highest bandwidth, not the lowest. This statement is misleading.
- B. Correct.
Correct: A composite metric considers multiple factors like bandwidth and delay. Even if one path is shorter, the overall metric of another path might be lower, causing the routing protocol to select it.
- C. Incorrect.
Incorrect: Some routing protocols like RIP use hop count as the sole metric, but this is not always the case for other protocols like EIGRP or OSPF. This depends on the routing protocol being used.
- D. Incorrect.
Incorrect: Administrative distance is a separate concept from metrics and is used to select between different routing protocols, not to select the shortest path within a single protocol.