CompTIA Network+ Practice Test

What happens to routing protocols with differing metrics for the same route?

1. They automatically choose the higher metric

2. They cannot be compared; administrative distances are used

3. They lead to routing loops

4. They result in network downtime

The correct answer is: They cannot be compared; administrative distances are used

When routing protocols have differing metrics for the same route, the comparison is determined by administrative distances rather than the metrics themselves. Each routing protocol is assigned an administrative distance, which is a value that indicates the reliability or trustworthiness of the route advertised by that protocol. When routers receive route updates from multiple routing protocols for the same destination, they compare the administrative distances of each route. The route with the lowest administrative distance is preferred and installed in the routing table. This means that while metrics, such as bandwidth or delay, can indicate the quality of a route, the ultimate decision on which route to use is based on the administrative distance. This relationship ensures that even if one protocol indicates a lower cost route based on its own metric, it may not always be selected if another protocol has a lower administrative distance, signifying it is more favorable overall. Therefore, understanding administrative distances is crucial for network professionals managing routing decisions and ensuring effective routing paths within a network.