Introduction to Administrative Distance


Administrative Distance (abbreviation for AD) is a value that routers/Layer 3 switches use in order to select the best path when there are more than 1 routes to the same destination from two different routing protocols.Administrative Distance (AD) is a numeric value which can range from 0 to 255 and is referred as standard for route preference across vendors.

Below table gives the default Administrative Distance for all the Routing protocols –






Connected 0 C
Static Route out an interface 0 S
Static Route to Next-Hop IP 1 S
EIGRP Summary route 5 D
External BGP 20 B
Internal EIGRP 90 D
IGRP 100 I
OSPF 110 O
IS-IS 115 i
RIP v1 & v2 120 R
Exterior Gateway Protocol (EGP) 140 E
ODR 160 O
External EIGRP 170 D EX
Internal BGP 200 B
Unknown 255

Watch the below given video for better understanding of Administrative distance:

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