How to Study Virtual Private Networks
CertificationZone has several Study Guides on Virtual Private Networks (VPN) and technologies closely associated with them. One of the challenges of VPNs, however, is to pin down just what they are and when they are useful.
Some of the general types of VPN you will encounter include RFC 2547 and its successor. This was originally designed with BGP signaling over MPLS transport, but it is now capable of running over different transports such as GRE and IPSec.
Before beginning to understand VPNs, you must internalize, make part of your gut instincts, that almost everything in modern networking is a virtualization.
This Study Guide starts you down that path by outlining the steps involved in learning VPNs.
For current Cisco certification exams, you'll need to know about several CE-VPNs and at least the 2547bis features deployed as of IOS 12.2.
After you get going, be sure to read the
Level Three VPNs
The Other VPNs