Chapter 16. Remote Access Virtual Private Networks (VPNs)

This chapter covers the following topics:

• VPN Basics

• Authentication

• Tunneling Protocols

• Encryption

• PGP

• PKI

• MD5

• IPSec

• IKE

• LAN-to-LAN VPN

• VPN Architecture

Remote access is best defined as providing access to fixed site resources for users who are not at a fixed workstation at that same site's Local Area Network (LAN). The largest remote access user community is mobile or telecommuting users, such as a sales force or field engineering team. Figure 16-1 illustrates a traditional remote access network using the Public Switched Telephone Network (PSTN) or the Integrated Services Digital Network (ISDN).

Figure 16-1. Traditional Remote Access (PSTN/ISDN Transport)

Traditional remote access connectivity is achieved with users dialing into a dedicated PSTN/ISDN modem pool, maintained either by a corporate IS/IT staff or by the network service provider. A secure alternative to traditional remote access is IP-based Virtual Private Networking (IP-VPN). With IP-VPNs, all connections to corporate intranets are calls to a local ISP, carried by the Internet to a corporate VPN gateway.