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:

ProtocolAdministrative distance
DHCP-learned254
Internal BGP200
External EIGRP170
ODR160
EGP140
RIP120
IS-IS115
OSPF110
IGRP100
Internal EIGRP90
External BGP20
EIGRP summary route5
Static route out an interfacece1 (There are some documents saying that this is actualy 0 but it is now … read this)
Static route to next-hop address1
Directly connected route0

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