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 "Levels in an IS-IS Network Topology" so that you can verify the configuration output of the various routers.

Figure 8: IS-IS Network Topology with Details

Steps To Take

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

1. Check the Configuration of a Level 1/Level 2 Router
2. Check the Configuration of a Level 1 Router
3. Check the Configuration of a Level 2 Router