The Problem
You have a corporate LAN. You want to set up a VPN (in this case OpenVPN) into the LAN for your road-warriors. However, your LAN is numbered with one of the very common private subnets, such as 192.168/16. Your road-warriors often get addresses in the same private subnet from their coffee-shops, and this breaks things horribly. This is illustrated in the diagram below.I'm going to use specific IP addresses and interface names on this page, since too often I find when people try to describe the general solution it actually makes it less clear and harder to apply to your own network.
