200-301 Question 284
Single answerYou are configuring a network with multiple routing protocols enabled, including OSPF, EIGRP, and RIP. A router receives the following routes to the same destination network (10.1.1.0/24):
- A route from OSPF with a metric of 20
- A route from EIGRP with a metric of 120
- A route from RIP with a metric of 5
Which route will the router prefer and install in its routing table?
- A
The OSPF route with a metric of 20
- B
The EIGRP route with a metric of 120
- C
The RIP route with a metric of 5
- D
The router will load balance between all three routes
Show answer and explanation
Correct answer: B
Explanation
Administrative distance (AD) is the primary factor used by routers to choose between routes from different routing protocols to the same destination. Lower AD values indicate higher trustworthiness. In this scenario, EIGRP has an AD of 90, OSPF has an AD of 110, and RIP has an AD of 120. Thus, the EIGRP route is selected, despite its metric being higher than OSPF and RIP, as AD takes precedence over metrics.
- A. Incorrect.
Incorrect. Although OSPF has a lower metric, the router does not use the metric alone to decide routing preference. Administrative distance is prioritized over metrics, and OSPF has an administrative distance of 110.
- B. Correct.
Correct. EIGRP has the lowest administrative distance (90) among the three protocols, making it the preferred route, regardless of its metric.
- C. Incorrect.
Incorrect. RIP has the highest administrative distance (120) among the three protocols, so it will not be chosen.
- D. Incorrect.
Incorrect. Load balancing only occurs if multiple routes with the same administrative distance and metric are available, which is not the case here.