IP Networking Unit 4 Cisco IOS Admin Distances Juniper JUNOS Route Preferences
Eric Worth (12729086)
01/14/15
NT2460 – IP Networking
Unit 4 – Cisco IOS Admin Distances & Juniper JUNOS Route Preferences
Administrative distance is the first criterion that a router uses to determine which routing protocol to use if two protocols provide route information for the same destination. Administrative distance is a measure of the trustworthiness of the source of the routing information. Administrative distance has only local significance, and is not advertised in routing updates.
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
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
One can modify the administrative distance of a protocol through the distance command in the routing process sub configuration mode. This command specifies that the administrative distance is assigned to the routes learned from a particular routing protocol. One needs to use this procedure generally when one migrates the network from one routing protocol to another, and the latter has a higher administrative distance. However, a change in the administrative distance can lead to routing loops and black holes. So, we gotta use caution if we change the administrative distance.
The values between Juniper and Cisco are very similar. The default values are a little slower with Juniper in some areas such as IS-IS and OSPF (intermediate system to immediate system and open shortest path first)
The OSPF routes (open shortest path first) in Cisco has no hop count limitations. The external for Cisco (EBGP) is 20 compares to Junos (BGP) with 170. Cisco is lower because it goes out as a
01/14/15
NT2460 – IP Networking
Unit 4 – Cisco IOS Admin Distances & Juniper JUNOS Route Preferences
Administrative distance is the first criterion that a router uses to determine which routing protocol to use if two protocols provide route information for the same destination. Administrative distance is a measure of the trustworthiness of the source of the routing information. Administrative distance has only local significance, and is not advertised in routing updates.
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
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
One can modify the administrative distance of a protocol through the distance command in the routing process sub configuration mode. This command specifies that the administrative distance is assigned to the routes learned from a particular routing protocol. One needs to use this procedure generally when one migrates the network from one routing protocol to another, and the latter has a higher administrative distance. However, a change in the administrative distance can lead to routing loops and black holes. So, we gotta use caution if we change the administrative distance.
The values between Juniper and Cisco are very similar. The default values are a little slower with Juniper in some areas such as IS-IS and OSPF (intermediate system to immediate system and open shortest path first)
The OSPF routes (open shortest path first) in Cisco has no hop count limitations. The external for Cisco (EBGP) is 20 compares to Junos (BGP) with 170. Cisco is lower because it goes out as a