Chapter 15. IP Tunneling to MPLS/VPN Migration Case Study

In Chapter 6, "MPLS Migration and Configuration Example," we examined a sample migration of the TransitNet service provider network to a backbone based on the MPLS architecture. The primary reason for this migration was to remove the necessity to hold external routing information within the core. However, a further reason for the migration was to allow the service provider to offer advanced and more scalable services, such as virtual private networks, to its customers, using the MPLS technology.

During this chapter, we will see the evolution of the migrated TransitNet MPLS network to support Virtual Private Networks (VPNs) using the MPLS architecture. The case study that follows provides a sample VPN migration from an IP tunneling deployment to an MPLS-based solution. The topology used within the case study is not meant to illustrate a fully redundant network and, therefore, does not consider all aspects of resiliency and redundancy in the design.

The goal of this case study is to provide an insight into the steps necessary for a successful migration and the preliminary pre-deployment network design that must occur before migration to an MPLS-based VPN solution. The sections that follow do not provide a full migration path or all the details that are necessary to move from one technology to another. However, they do provide pointers on some of the necessary actions and can be used as a template when planning for this type of migration.

For simplicity, the example shows a VPN service that is provided to only one large customer, called SampleNet, although multiple customers could be supported using the same model. Many of the techniques described within this example can be used across multiple topologies and network deployment requirements.

Figure 15-1 provides a reminder of the migrated TransitNet MPLS backbone network, which we reviewed during Chapter 6. For simplicity, only one Internet exit point is shown within the topology, and the physical connectivity of the BGP route reflectors is not provided.