Administrative Distance (AD) values in Cisco & Juniper

AD value is a reliability or trustworthiness of a protocol, for selecting routes to be placed in routing table.

If a router has routes to same destination from two different protocols it will prefer the protocol with lowest AD value, and its routes will be installed in the Routing / Forwarding table.

Cisco and Juniper use different values of AD for their selection criteria. Below is the comparison chart taken from their respective websites.

Default Distance Value Table

This table lists the administrative distance default values of the protocols that Cisco supports:

Route Source

Default Distance Values

Connected interface 0
Static route 1
Enhanced Interior Gateway Routing Protocol (EIGRP) summary route 5
External Border Gateway Protocol (BGP) 20
Internal EIGRP 90
IGRP 100
OSPF 110
Intermediate System-to-Intermediate System (IS-IS) 115
Routing Information Protocol (RIP) 120
Exterior Gateway Protocol (EGP) 140
On Demand Routing (ODR) 160
External EIGRP 170
Internal BGP 200
Unknown* 255

* If the administrative distance is 255, the router does not believe the source of that route and does not install the route in the routing table.

Default Route Preference Values

The JUNOS software routing protocol process assigns a default preference value to each route that the routing table receives. The default value depends on the source of the route. The preference is a value from 0 through 255, with a lower value indicating a more preferred route. Table 2 lists the default preference values.

Table 2: Default Route Preference Values

How Route Is Learned

Default Preference

Statement to Modify Default Preference

Directly connected network 0
System routes 4
Static 5 static
MPLS 7 MPLS preference in the JUNOS MPLS Applications Configuration Guide
LDF 8 LDF preference in the JUNOS MPLS Applications Configuration Guide
LDP 9 LDP preference in the JUNOS MPLS Applications Configuration Guide
OSPF internal route 10 OSPF export
IS-IS Level 1 internal route 15 IS-IS external-preferencepreference
IS-IS Level 2 internal route 18 IS-IS external-preferencepreference
Default 20
Redirects 30
Kernel 40
Router Discovery 55
RIP 100 RIP preference
RIPng 100 RIPng preference
PIM 105 JUNOS Multicast Protocols Configuration Guide
DVMRP 110 JUNOS Multicast Protocols Configuration Guide
Routes to interfaces that are down 120
Aggregate 130 aggregate
OSPF AS external routes 150 OSPF external-preferencepreference
IS-IS Level 1 external route 160 IS-IS external-preferencepreference
IS-IS Level 2 external route 165 IS-IS external-preferencepreference
BGP 170 BGP preferenceexportimport
MSDP 175 JUNOS Multicast Protocols Configuration Guide

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