VPNs can be created using technologies from Layer 2 or Layer 3. Layer 2 technologies are simpler than one of the two Layer 3 technologies. The other Layer 3 approach actually uses the same underlying concept as the various Layer 2 approaches: a logical tunnel for the traffic to hide in. All the Layer 2 technologies, and the Layer 3 tunnel approach, are sometimes described as an "envelope-within-an-envelope" approach: they encapsulate the packet in a tunneling header, which is further encapsulated in the regular Layer 2 or Layer 3 header. The idea is to hide the contents at least a little, inside an extra layer of encapsulation, while preserving a distinct traffic identifier in the additional header. All the Layer 2 or Layer 3 traffic is multiplexed on the same wire but distinguished internally by the extra header. In this week's Zone Newsletter article, Annlee Hines reviews Layer 2 technologies.

View Layer 2 VPNs A Tutorial excerpt from The Other VPNs: It's Not All MPLS by Annlee Hines

Did you know the brand new "Other VPNs" Study Guide that Certification Zone unveiled on July 1 is the seventh Zone Study Guide written by networking expert Annlee Hines? Gain a better understanding of Annlee by reading this week's Zone Interview. In it, Annlee discusses the different real-life scenarios that make it necessary to understand VPNs and also offers some nuts and bolts advice about security, consulting, and networking in general.

View Interview with the Author - Annlee Hines