Network Security Fundamentals

Chapter 12. Virtual Private Networks

On completing this chapter, you will be able to

• Explain IPSec

• Describe the difference between transport mode and tunnel mode

• Explain transform sets

• Understand the difference between ESP and AH

• Describe antireplay protection

A virtual private network (VPN) is a service that offers a secure, reliable connection over a shared public infrastructure such as the Internet. Cisco defines a VPN as an encrypted connection between private networks over a public network. To date, there are three types of VPNs:

• Remote access

• Site-to-site

• Firewall-based

The remote access VPN solution is shown in Figure 12-1. Telecommuters and mobile phone users use remote access VPNs to work on the corporate network while out of the office.

Figure 12-1. Remote ...