Question

A Cisco router has learned a network via three different routing protocols: OSPF, EIGRP, and RIP. Which route will the router believe (that is, inject into the router's IP routing table)?

a) OSPF
b) EIGRP
c) RIP
d) The router will use administrative distance to decide

Answer 1

A Cisco router will choose the route with the lowest administrative distance among the routing protocols OSPF, EIGRP, and RIP to inject into its IP routing table.

Step-by-step explanation:

A Cisco router will choose the route to believe (i.e., inject into the router's IP routing table) based on the administrative distance of the routing protocols. Each routing protocol has a default administrative distance value, which indicates the trustworthiness of the protocol. The Cisco router will select the route with the lowest administrative distance value.

In the given scenario, OSPF has an administrative distance of 110, EIGRP has an administrative distance of 90, and RIP has an administrative distance of 120. Therefore, EIGRP is the route that the Cisco router will believe and inject into its IP routing table since it has the lowest administrative distance among the three routing protocols.

Administrative distance is used by routers to choose the best route when more than one routing protocol has learned the same network. The lower the administrative distance, the more trustworthy the routing protocol is considered by the router.