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Verify IP Addressing
Purpose
When you investigate the IP layer, you verify that interfaces have correct IP addressing, and that OSPF neighbors or IS-IS adjacencies are established. In this example, an IP address is configured incorrectly on the ingress router (R1).
Action
To verify IP addressing, enter the following command from the ingress, transit, and egress routers:
user@host> show interfaces
terse
Sample Output
user@R1> show interfaces terse
Interface Admin Link Proto Local Remote
so-0/0/0 up up
so-0/0/0.0 up up inet 10.1.12.1/30
iso
mpls
so-0/0/1 up up
so-0/0/1.0 up up inet 10.1.15.1/30
iso
mpls
so-0/0/2 up up
so-0/0/2.0 up up inet 10.1.13.2 <<< Incorrect IP address
iso
mpls
lo0 up up
lo0.0 up up inet 10.0.0.1
iso 49.0004.1000.0000.0001.00
user@R3> show interfaces terse
Interface Admin Link Proto Local Remote
so-0/0/0 up up
so-0/0/0.0 up up inet 10.1.34.1/30
iso
mpls
so-0/0/1 up up
so-0/0/1.0 up up inet 10.1.23.2/30
iso
mpls
so-0/0/2 up up
so-0/0/2.0 up up inet 10.1.13.2/30 <<< Identical to R1
iso
mpls
so-0/0/3 up up
so-0/0/3.0 up up inet 10.1.36.1/30
iso
mpls
lo0 up up
lo0.0 up up inet 10.0.0.3
iso 49.0004.1000.0000.0003.00
user@R6> show interfaces terse
Interface Admin Link Proto Local Remote
so-0/0/0 up up
so-0/0/0.0 up up inet 10.1.56.2/30
iso
mpls
so-0/0/1 up up
so-0/0/1.0 up up inet 10.1.46.2/30
iso
mpls
so-0/0/2 up up
so-0/0/2.0 up up inet 10.1.26.2/30
iso
mpls
so-0/0/3 up up
so-0/0/3.0 up up inet 10.1.36.2/30
iso
mpls
lo0.0 up up inet 10.0.0.6
iso 49.0004.1000.0000.0006.00
Meaning
The sample output shows that the IP addresses for interface so-0/0/2.0 on R1 and interface so-0/0/2.0 on R3 are identical. Interface IP addresses within a network must be unique for the interface to be identified correctly.
