Verify the IS-IS Configuration
Purpose
When you have determined that the problem is probably at the IS-IS protocol level, check the IS-IS configuration of the routers in your network.
Action
To verify the IS-IS configuration, enter the following command from the relevant routers:
Sample Output
user@R1> show configuration protocols isis
level 1 disable;
interface so-0/0/0.0;
interface so-0/0/1.0;
interface so-0/0/2.0;
interface lo0.0; {
passive
user@R3> show configuration protocols isis
level 1 disable;
interface all {
level 2 metric 10;
}
interface fxp0.0 {
disable;
}
interface lo0.0; {
passive
user@R6> show configuration protocols isis
level 2 disable; <<< Incorrect level disabled
interface all {
level 2 metric 10;
}
interface fxp0.0 {
disable;
}
interface lo0.0; {
passive
Meaning
The sample output shows that R6 has Level 2 disabled, while R1 and R3 have Level 1 disabled. For IS-IS adjacencies to establish, routers need to be at the same level. Another common configuration error is to omit the loopback interface (lo0) from the configuration at the [edit protocols isis] hierarchy level. IS-IS does not function correctly if the loopback interface (lo0) is not configured at this level. In addition, including the passive statement ensures that protocols are not run over the loopback interface (lo0) and that the loopback interface (lo0) is advertised correctly throughout the network.
