In Chapter 9, "MPLS/VPN Architecture Operation," we discussed the basic MPLS/VPN intranet connectivity model and learned that, in many cases, this type of solution will be adequate in providing VPN connectivity for a single organization. However, it is clear that a large majority of deployments that use the MPLS/VPN architecture will need advanced features to satisfy their topology and service requirements, and also will need to be provided with connectivity to other organizations.
Depending on the actual requirements of the network design, numerous topologies can be deployed using the MPLS/VPN architecture and its associated tools. There are too many scenarios to be able to provide examples for each and every one; instead, this chapter aims to present some of the more widely used topologies, several of which were introduced in Chapter 7, "Virtual Private Network (VPN) Implementation Options."