Display the Status of IS-IS Adjacencies

Purpose

Assuming that all the routers are correctly configured for IS-IS, you can verify which neighbors are adjacent and able to exchange IS-IS data. In addition, you can examine the set of routes installed in the forwarding table to verify that the routing protocol process (rpd) has relayed the correct information into the forwarding table.

Figure 9 illustrates the example IS-IS topology used for the procedures in this section.

Figure 9: IS-IS Network Topology

The network consists of Level 1 and Level 2 adjacencies. Level 1 adjacencies are within areas 49.0001 and 49.0002. Level 2 adjacencies occur between all directly connected Level 2 routers regardless of which area they are in. For example, R5 is in area 49.0001, R6 is in area 49.0003, R1 is in area 49.0004, and R2 is in area 49.0002. The network in Figure 9 should have the following adjacencies:

• Level 2 adjacencies between all directly connected Level 2 routers (R1, R2, R5, and R6).
• Level 1 adjacencies between routers in area 49.0001 (R4 and R5) and between routers in area 49.0002 (R2 and R3).

Steps To Take

To verify that routers are adjacent and able to exchange IS-IS data, follow these steps:

1. Verify Adjacent Routers
2. Examine a Route
3. Examine the Forwarding Table
4. Examine the Link-State Database
5. Examine a Link-State Protocol Data Unit Header