Step 3: Check the Configuration of a Level 2 Router

Action

To check the configuration of a Level 2 router, enter the following CLI commands:

user@host# [edit protocols isis] show

user@host# [edit protocols isis] run show isis interface

user@host# [edit] edit interfaces

user@host# [edit interfaces] show

Sample Output:

The following sample output is for R6, a Level 2 router in the network shown in Figure 7:

[edit protocols isis]

user@R6# show 

level 1 disable;

interface so-0/0/0.0 {

    level 2 metric 10;

}

interface so-0/0/2.0 {

    level 2 metric 10;

}

interface fxp0.0 {

    disable;

}

interface lo0.0;

[edit protocols isis]

user@R6# run show isis interface 

IS-IS interface database:

Interface             L CirID Level 1 DR        Level 2 DR        L1/L2 Metric

lo0.0                 0   0x1 Passive           Passive                 0/0

so-0/0/0.0            2   0x1 Disabled          Point to Point         10/10

so-0/0/2.0            2   0x1 Disabled          Point to Point         10/10

[edit interfaces]

user@R6# show 

so-0/0/0 {

    unit 0 {

        family inet {

            address 10.1.56.2/30;

        }

        family iso;

    }

}

so-0/0/2 {

    unit 0 {

        family inet {

            address 10.1.26.2/30;

        }

        family iso;

    }

}

lo0 {

    unit 0 {

        family inet {

            address 10.0.0.6/32;

        }

        family iso {

            address 49.0003.1000.0000.0006.00;

        }

    }

}

What It Means

The sample output shows a basic configuration of IS-IS on R6, a Level 2 router. The basic configuration is at the [edit protocols isis] and [edit interfaces] hierarchy levels.

At the [edit protocols isis] level, four interfaces are included: so-0/0/0.0, so-0/0/2.0, fxp0, and the loopback (lo0) interface. Level 1 is disabled on the two SONET interfaces, making this a Level 2 router that routes between areas and towards other ASs. The management interface (fxp0) is disabled so that IS-IS packets are not sent over it, and the loopback interface (lo0) is included because it becomes a point of connection from the router to the IS-IS network.

At the [edit interfaces] hierarchy level, the interfaces included in the [edit protocols isis] hierarchy level are also configured with family iso, and the loopback (lo0) interface is configured with the NET address of 49.0003.1000.0000.0006.00. Every router in an IS-IS network must have at least one NET address that identifies a point of connection to the IS-IS network. The NET address is generally configured on the loopback (lo0) interface. Routers that participate in multiple areas can have multiple NET addresses.

See the JUNOS Routing Protocols Configuration Guide for more information on configuring IS-IS on a router.