Step 3: Configure OSPF as the IGP

Purpose

Before you can run MPLS on your network, you must have an IGP running on all specified routers and interfaces. The IGP can be either OSPF or IS-IS. For the steps to configure IS-IS, see Configure IS-IS as the IGP.

Figure 3: OSPF Network Topology

The OSPF IGP in the MPLS network in Figure 2 consists of the following:

• All routers are configured for the backbone OSPF area 0.0.0.0.
• All routers have the RID manually configured to avoid possible problems when the OSPF RID changes; for example, when multiple loopback addresses are configured.
• All routers have traffic engineering enabled. When traffic engineering is enabled for OSPF, the SPF algorithm takes into account the various LSPs configured under MPLS and configures OSPF to generate link-state advertisements (LSAs) that carry traffic engineering parameters. These routes are installed into the primary routing table inet.0, but the LSPs are installed by default into the inet.3 routing table.
• Adjacencies between all OSPF neighbors are 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 OSPF as the IGP, you must enable OSPF and traffic engineering on the router. We also recommend that you manually configure the RID and include the loopback interface (lo0) at the [edit protocols ospf] hierarchy level.

You can enable OSPF throughout the rest of the network by repeating this step as appropriate on other routers until all routers and interfaces establish OSPF neighbors.

Steps To Take

To configure OSPF and establish OSPF neighbors, follow these steps:

1. Enable OSPF on Routers in Your Network
2. Verify That OSPF Neighbors Are Established