The missing return route

After setting up OpenVPN successfully for the very first time, it is very common to misconfigure the network routes for the VPN. In this recipe, we will first set up a basic TUN-style VPN as is done in Chapter 2, Client-server IP-only networks. At first, routing will not work until the right routes are added. The purpose of this recipe is to describe how to troubleshoot such a routing error.

Getting ready

We use the following network layout:

Install OpenVPN 2.0 or higher on two computers. Make sure the computers are connected over a network. Set up the client and server certificates using the first recipe from Chapter 2, Client-server IP-only Networks. For this recipe, the server computer was running CentOS 5 Linux and OpenVPN 2.1.1. The client was running Fedora 13 Linux and OpenVPN 2.1.1. Keep the configuration file, basic-udp-server.conf, from the Chapter 2 recipe Server-side routing at hand, as well as the client configuration file, basic-udp-client.conf, from the...