Fundamentals of Routing
33
Administrative Distances
When configuring routing protocols, you need to be aware of administrative
distances. These are used to rate the trustworthiness of routing information
received on a router from a neighbor router. An administrative distance is an
integer from 0 to 255, where 0 is the most trusted and 255 means no traffic
will be passed via this route.
Table 2.1 shows the default administrative distances that a Cisco router
will use to decide which route to take to a remote network.
T A B L E 2 . 1
Default Administrative Distances
Route Source
Default Distance
Connected interface
0
Static route
1
EIGRP summary
5
External BGP
20
EIGRP
90
IGRP 100
OSPF
110
IS-IS
115
RIP
120
EDP
140
External EIGRP
170
Internal BGP
200
Unknown
255 (This route will never be used.)
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