Verify the IS-IS Configuration on a Router in a Network

Purpose

For IS-IS to run on a router (intermediate system) in your network, you must enable IS-IS on the router, configure a network entity title (NET) on the loopback interface (lo0), and configure family iso on all interfaces on which you want to run IS-IS. When you enable IS-IS on a router, Level 1 and Level 2 are enabled by default.

Figure 7 illustrates an example of routers at different levels in an IS-IS topology.

Figure 7: Levels in an IS-IS Network Topology

The network in Figure 7 is organized hierarchically and consists of Level 2, Level 1/Level 2, and Level 1 routers in one autonomous system (AS) divided into four areas: 49.0001, 49.0002, 49.0003, and 49.0004. The Level 2 routers route toward other autonomous systems. The Level 1/Level 2 routers route between areas and to other autonomous systems. The Level 1 routers route within an area, and when the destination is outside the local area, they route toward a Level1/Level2 system.

In the following steps, the configuration of the various types of routers is examined.

Figure 8 provides more details about the IS-IS network topology on Figure 7 so that you can verify the configuration output of the various routers.

Figure 8: IS-IS Network Topology with Details

To verify that IS-IS is configured correctly on routers at different levels, follow these steps:

Check the Configuration of a Level 1/Level 2 Router

Purpose

To check the configuration of a Level 1/Level 2 router.

Action

To verify the IS-IS configuration of a Level 1/Level 2 router in your network, enter the following Junos OS command-line interface (CLI) commands:

user@host# [edit protocols isis] showuser@host# [edit protocols isis]run show isis interfaceuser@host# [edit] edit interfacesuser@host# [edit interfaces] show

The following output is for an IS-IS configuration on R2, a Level 1/Level 2 router in the network shown in Levels in an IS-IS Network Topology:

Sample Output

[edit protocols isis]
user@R2# show          
interface so-0/0/0.0 {
    level 2 metric 10;
     level 1 disable;
}
interface so-0/0/1.0 {
    level 2 disable;
    level 1 metric 10;
}
interface so-0/0/2.0 {
    level 2 metric 10;
     level 1 disable;
}
interface fxp0.0 {
    disable;
}
interface lo0.0;

[edit protocols isis]
user@R2# 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-0/0/1.0            3   0x1 Point to Point    Point to Point         10/10
so-0/0/2.0            2   0x1 Disabled          Point to Point         10/10
[edit interfaces]

user@R2# show 
so-0/0/0 {
    unit 0 {
        family inet {
            address 10.1.12.2/30;
        }
        family iso;
    }
}
so-0/0/1 {
    unit 0 {
        family inet {
            address 10.1.23.1/30;
        }
        family iso;
    }
}
so-0/0/2 {
    unit 0 {
        family inet {
            address 10.1.26.1/30;
        }
         family iso;
    }
}
lo0 {
    unit 0 {
        family inet {
            address 10.0.0.2/32;
        }
         family iso {
            address 49.0002.1000.0000.0002.00;
        }
    }
}

Meaning

The sample output shows a basic configuration of IS-IS on R2, a Level 1/Level 2 router. The basic configuration is at the [edit protocols isis] and [edit interfaces] hierarchy levels.

At the [edit protocols isis] level, five interfaces are included: so-0/0/0, so-0/0/1, so-0/0/2, fxp0, and the loopback (lo0) interface. Two interfaces, so-0/0/0.0 and so-0/0/2.0, have Level 1 disabled, making them Level 2 interfaces. One interface, so-0/0/1.0, has Level 2 disabled, making it a Level 1 interface. 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, all of the interfaces included in the [edit protocols isis] hierarchy level are configured with family iso, and the loopback (lo0) interface is configured with the NET address 49.0002.1000.0000.0002.00. 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.

Check the Configuration of a Level 1 Router

Purpose

To check the configuration of a Level 1 router.

Action

To check the configuration of a Level 1 router, enter the following CLI commands:

user@host# [edit protocols isis] showuser@host# [edit protocols isis] run show isis interfaceuser@host# [edit] edit interfacesuser@host# [edit interfaces] show

The following sample output is for R4, a Level 1 router in the network shown in Levels in an IS-IS Network Topology:

Sample Output

[edit protocols isis]

user@R4# show 
level 2 disable;
interface  so-0/0/2.0 {
    level 1 metric 10;
}
interface fxp0.0 {
    disable;
}
interface lo0.0;
[edit protocols isis]

user@R4# 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-0/0/2.0            1   0x1 Point to Point     Disabled               10/10
[edit interfaces]

user@R4# show 
so-0/0/2 {
    unit 0 {
        family inet {
            address 10.1.45.1/30;
        }
         family iso;
    }
}
lo0 {
    unit 0 {
        family inet {
            address 10.0.0.4/32;
        }
         family iso {
            address 49.0001.1000.0000.0004.00;
        }
    }
}

Meaning

The sample output shows a basic configuration of IS-IS on R4, a Level 1 router. The basic configuration is at the [edit protocols isis] and [edit interfaces] hierarchy levels.

At the [edit protocols isis] hierarchy level, three interfaces are included: so-0/0/2.0, fxp0, and the loopback (lo0) interface. Level 2 is disabled on the router, making it a Level 1 router that sends packets within its local area, 49.0001. When a packet destination is outside the local area, R4 establishes an adjacency with the nearest Level 1/Level 2 router (R5) that forwards the packets. For more information on adjacencies, see Display the Status of IS-IS Adjacencies .

One interface, so-0/0/2.0, is configured for IS-IS. 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 interface included in the [edit protocols isis] hierarchy level is also configured with family iso, and the loopback (lo0) interface is configured with the NET address of 49.0001.1000.0000.0004.00. 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.

Check the Configuration of a Level 2 Router

Purpose

To 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] showuser@host# [edit protocols isis] run show isis interfaceuser@host# [edit] edit interfacesuser@host# [edit interfaces] show

The following sample output is for R6, a Level 2 router in the network shown in Levels in an IS-IS Network Topology:

Sample Output

[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;
        }
    }
}

Meaning

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.