AD VALUE (Administrative distance){0-255}

Administrative distance (AD) is an arbitrary numerical value assigned to a routing protocol, a static route or a directly-connected route based on its perceived quality of routing. The administrative distance (AD) value is often used by Cisco routers to determine the "best" route that should be used when multiple paths to the same destination exist. A routing protocol with a lower administrative distance is considered "better" and is given priority over routing protocols with higher administrative distances. The "better" route is selected by the router and is inserted into the router's routing table to be used to route traffic. For example, routes issued by EIGRP are considered more reliable than routes issued by RIP. This is because EIGRP has an administrative distance of 90 while RIP has an administrative distance of 120. The administrative distance (AD) value may be set manually by a network administrator. If a network administrator fails to properly set the administrative distance or configures multiple routing protocols with the same administrative distance, the router will use the default administrative distance.