In this chapter we will have a look at the syntax of the command-line tool openvpn, which enables us to build tunnels quickly. By analyzing the standard configuration file we used to set up a tunnel with a pre-shared key, we will now dive into the depths of the configuration options of openvpn. This way, we will learn about basic tunnel network setup and control, compression, and debug output.

As a next step, the configuration file containing the certificate-based tunnel created in Chapter 6 will be in our focus. From then on we will go through several groups of parameters that can be given to openvpn (be it in a configuration file or at the command-line prompt). We will deal with examples for many of these parameters and look at scenarios where they might prove helpful. Parameters available in server and client mode, encryption, and Windows-specific options are explained.

Many of the following options are explained in detail on the...