Chapter 9. Virtual Private Networks
Virtual private networks (VPNs) of all types are a growing area of network design and deployment. VPNs are used for a wide variety of tasks, from connecting remote users to the corporate network to interconnecting corporate sites. Using VPNs to interconnect sites, building a network on top of a service provider infrastructure, is the focus of this chapter.
NOTE
This chapter does not cover carrying VPN information through routing protocols, such as how Open Shortest Path First (OSPF) and Intermediate System-to-Intermediate System (IS-IS) interact with Multiprotocol Label Switching (MPLS) to create MPLS/traffic engineering (TE).
The chapter begins with a look at three options for routing over an MPLS VPN and then delves into IPSec and general routing encapsulation (GRE) tunnels and some of the implications of routing over these types of tunnels in a network. The chapter concludes with a look at the Next Hop Resolution Protocol (NHRP) and the interaction between NHRP and GRE tunnels.
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