Step 1: Verify Adjacent Routers

Action

To verify that routers are adjacent and able to exchange IS-IS data, enter the following CLI operational mode command:

user@host> show isis adjacency 

Sample Output

The following sample output shows the adjacencies that formed for all routers shown in Figure 9:

user@R1> show isis adjacency 

Interface             System         L State        Hold (secs) SNPA

so-0/0/0.0            R2            2 Up                   19

so-0/0/1.0            R5            2 Up                   18

user@R2> show isis adjacency 

Interface             System         L State        Hold (secs) SNPA

so-0/0/0.0            R1            2 Up                   19

so-0/0/1.0            R3            1 Up                   26

so-0/0/2.0            R6            2 Up                   21

user@R3> show isis adjacency 

Interface             System         L State        Hold (secs) SNPA

so-0/0/1.0            R2            1 Up                   24

user@R4> show isis adjacency 

Interface             System         L State        Hold (secs) SNPA

so-0/0/2.0            R5            1 Up                   23

user@R5> show isis adjacency 

Interface             System         L State        Hold (secs) SNPA

so-0/0/0.0            R6            2 Up                   22

so-0/0/1.0            R1            2 Up                   20

so-0/0/2.0            R4            1 Up                   20

user@R6> show isis adjacency 

Interface             System         L State        Hold (secs) SNPA

so-0/0/0.0            R5            2 Up                   21

so-0/0/2.0            R2            2 Up                   20

What It Means

The sample output shows the adjacencies that formed in the network illustrated in Figure 9. The Level 1/Level 2 routers (R2 and R5) formed Level 1 adjacencies with Level 1 routers (R3 and R4), and Level 2 adjacencies with the Level 2 routers (R1 and R6). To view the status of the adjacency, examine the State column. In this example, all adjacencies in the network are up.

If the state is not Up for a particular neighbor, you must first examine the IS-IS configuration for the particular interface. Make sure that the NET address is correct and that the loopback (lo0) interface is configured. Use the show isis interface or show isis interface detail command to display the IS-IS parameters for all interfaces configured with IS-IS. With these two commands, you can see which interfaces are configured for IS-IS, whether they are configured for Level 1 or Level 2, the IS-IS metric, and other IS-IS information.