Administrative distance

Administrative distance (AD) influences the decision on which routing protocol the router should trust:

  1. AD can be modified.
  2. AD is only locally significant to the router, other router’s AD of routing protocol might be modified.
  3. Router will use the routing protocol that has the lowest AD to make routing decision.

Default Administrative distance of various routing protocols:

Directly connected = 0

Static route = 1

EIGRP summary = 5

External BGP (eBGP) = 20

EIGRP = 90

IGRP = 100 (Still exists?)

OSPF = 110

IS-IS = 115

RIP = 120

On Demand Routing (ODR) = 160

External EIGRP = 170

Internal BGP (iBGP) = 200

Unknown = 255



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