In this recipe, we will analyze the performance of an OpenVPN setup using the tcpdump utility. It is also possible to use the Wireshark utility, which is available for Linux, Windows, and Mac OS X. While this recipe does not cover any new OpenVPN functionality, it is useful to show how such an analysis can be made.
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 example9-6-server.conf from the recipe Tuning UDP based connections at hand, as well as the client configuration, example9-6-client.conf, from the same recipe.