This chapter covers the following topics:
- VPN Basics
- Types of IPsec VPNs
- IPsec Modes of Operation and Security Options
- Topology Considerations
- Design Considerations
- Site-to-Site Deployment Examples
- IPsec Outsourcing
Oh, how much is today hidden by science! Oh, how much it is expected to hide!
Friedrich Nietzsche, The Genealogy of Morals, 1887
Private information is practically the source of every large modern fortune.
Oscar Wilde, An Ideal Husband, 1895
Virtual private networks (VPNs) are a means to establish a private network over any other network. Typically, the "other" network is deemed insecure, so traffic sent over it requires some kind of extra protection. The most common example of this is a VPN between an organization's sites and users across the Internet. The rest of this chapter assumes this is the kind of VPN you want.