What is used to determine which route will be added to R1's routing table when multiple routes are learned from different routing protocols?

When a router learns multiple routes to the same destination from different routing protocols, it uses Administrative Distance (AD) to determine which route to add to the routing table. AD is a value assigned to each routing protocol that indicates its trustworthiness; lower values indicate more reliable routes. For instance, a directly connected route has an AD of 0, while a static route has a value of 1, and routes learned via OSPF have an AD of 110.

When the router compares routes from different protocols, it will prioritize the route with the lowest AD. In contrast, other metrics such as bandwidth or load are factors that influence the performance of the routes, but they do not affect the decision process of which route enters the routing table; they are often used within routing protocols to select the best path once protocols have been evaluated based on their AD.