Step 2: Configure IS-IS as the IGP
Purpose
Before you can run MPLS on your network, you should have an IGP running on all specified routers and interfaces. The IGP can be either IS-IS or OSPF. For the steps to configure OSPF, see Configure OSPF as the IGP.
The IS-IS IGP in the MPLS network in Figure 2 consists of the following:
- All routers are configured for Level 2, therefore default CSPF LSPs can occur.
- All routers are in IS-IS area 49.0004. However, the routers in this network could be in any area because Level 2 adjacencies occur between all directly connected Level 2 routers regardless of which area they are in.
- Level 2 adjacencies between all directly connected Level 2 routers as follows:
- R1 is adjacent to R2, R3, and R5
- R2 is adjacent to R1, R3, R4, and R6
- R3 is adjacent to R1, R2, R4, and R6
- R4 is adjacent to R2, R3, R5, and R6
- R5 is adjacent to R1, R4, and R6
- R6 is adjacent to R2, R3, R4, and R5
When you configure IS-IS as the IGP, you must enable IS-IS on the router, configure International Organization for Standardization (ISO) addressing, and enable IS-IS on all router interfaces.
You can enable IS-IS throughout the rest of the network by repeating Step 1, Enable IS-IS on Routers in Your Network through Step 3, Enable IS-IS on Router Interfaces as appropriate on other routers until all routers and interfaces establish IS-IS adjacencies.
Steps To Take
To configure IS-IS and establish IS-IS adjacencies, follow these steps: