Administrative distance – Which route is the best?

Administrative distance is the measure used by Cisco routers to help them decide how to select the best path when there’s more that one route to the same destination from different routing protocols. We can say that in this manner administrative distance shows the real reliability of a routing protocol in one system. It shows which routes are more important based on the routing protocol from which they derived. Each routing protocol is prioritized in order of most to least reliable using an administrative distance value. Don’t get confused, a lower numerical value is preferred. For example, an EIGRP with an administrative distance of 90 will be chosen over a RIP route with an administrative distance of 120 and over OSPF route with an administrative distance of 110 to.

Here is a table with all default administrative distances used by Cisco routers:

Protocol Administrative distance
DHCP-learned 254
Internal BGP 200
External EIGRP 170
ODR 160
EGP 140
RIP 120
IS-IS 115
OSPF 110
IGRP 100
Internal EIGRP 90
External BGP 20
EIGRP summary route 5
Static route out an interfacece 1 (There are some documents saying that this is actualy 0 but it is now … read this)
Static route to next-hop address 1
Directly connected route 0

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