CCIE Practical Studies: Security (CCIE Self-Study)

Administrative Distance

The following is an area of concern when redistributing routes: What happens when your router learns a route to the same destination using both routing protocols? Which route will be selected over the other, or is it possible to create a routing loop? Adding to this dilemma is the fact that each protocol uses its own metric type to determine the best route, making it impossible to compare routes with different metric types. To alleviate this problem, Cisco IOS Software uses the administrative distance of the route to determine which one is placed in the routing table. Administrative distances are assigned so that the routing table can ensure that the route from the most preferred source is chosen as the best path.

While ...