Summary

In this chapter, you learned about service provider-based VPNs and enterprise VPNs, the functional and technological categories, and the data link layer and network layer VPNs. The PPTP and L2TP second layer VPNs are explained in reasonable detail. The main focus of the chapter is on remote access VPNs, and especially IPSec-based remote access VPN solutions, because they represent the vast majority of the existing VPN solutions in today's industry. The IPSec sections include security associations, security policies, IKE and IPSec modes and protocols, such as the AH and ESP. The authentication includes group name and password, client, user and message authentication methods, and certificates. The DH exponential algorithm, and the complex hashing and encryption complex mathematical algorithms are represented.