Linux Networking Cookbook

9.1. Setting Up a Safe OpenVPN Test Lab

Problem

You don't want to be messing around with trying to test OpenVPN over the Internet; you want a safe, controlled environment for testing before you deploy it.

Solution

Not a problem. Just build a little test lab with three computers. One acts as the remote PC, the second one is the OpenVPN server and router, and the third one represents your LAN. The PC acting as the OpenVPN server and router needs two Ethernet interfaces. With this setup, you can test OpenVPN configurations and firewall rules safely, and in a realistic manner. These should be in physical proximity to each other because when you start messing with networking, you're going to lose connectivity. You should use Ethernet cables and a switch; don't try this with wireless unless you enjoy introducing more problems.

Before you do anything else, install OpenVPN on the remote PC and the machine that is going to be your OpenVPN server. In this recipe, all three computers are running Linux. (We'll get to other clients later in the chapter.) OpenVPN is included in most Linux distributions, so it's just a yum install openvpn or aptitude install openvpn away.

Setting up routes can get a bit confusing, especially if you still rely on cheat sheets for calculating subnets (like I do), and have to draw network diagrams even for simple setups (which I must also do), so take it slowly and follow these steps exactly. You can always change addresses and routes later. Your test network should look ...