Routing Administrative Distances

Routing Administrative Distances

The administrative distance is a number assigned to a source of routing information (such as a static route or a specific routing protocol). The router uses these values to select the source of information to use when multiple routes to a destination exist. A smaller number indicates a more trusted route. The following table shows the default administrative values for a Cisco router.

Route Source	Administrative Distance
Connected interface	0
Static route	1
EIGRP summary route	5
EIGRP internal route	90
IGRP	100
OSPF	110
RIP	120
EIGRP external route	170

Note: You can modify how routes are selected by modifying the administrative distance associated with a source.

Routers can learn about routes to other networks using multiple routing protocols. In addition, there might be multiple paths between any two points. When making routing decisions, the router uses the following criteria for choosing between multiple routes:

1. If a router has learned of two routes to a single network through different routing protocols (such as RIP and OSPF), it will choose the route with the lowest administrative distance (OSPF in this example).
2. If a router has learned of two routes through the same protocol (for example two routes through EIGRP), the router will choose the route that has the best cost as defined by the routing metric (for EIGRP the link with the highest bandwidth and least delay will be used).