In this chapter, you learned about virtual private networks (VPNs) as an alternative to expensive private WAN solutions providing confidentiality, integrity, authentication, and anti-replay protection for user data.

We introduced basic VPN concepts covering encryption techniques that are at the core of any VPN implementation. We then introduced IPsec and SSL VPNs as one of the most popular VPN deployments today.

We closed the chapter by mentioning a few other IP tunneling protocols including L2F, PPTP, L2TP, and GRE.

We also covered configuration of GRE tunnels building on a simple serial link configuration.