Book Image

Mastering OpenVPN

By : Jan Just Keijser, Eric F Crist
Book Image

Mastering OpenVPN

By: Jan Just Keijser, Eric F Crist

Overview of this book

Security on the internet is increasingly vital to both businesses and individuals. Encrypting network traffic using Virtual Private Networks is one method to enhance security. The internet, corporate, and “free internet” networks grow more hostile every day. OpenVPN, the most widely used open source VPN package, allows you to create a secure network across these systems, keeping your private data secure. The main advantage of using OpenVPN is its portability, which allows it to be embedded into several systems. This book is an advanced guide that will help you build secure Virtual Private Networks using OpenVPN. You will begin your journey with an exploration of OpenVPN, while discussing its modes of operation, its clients, its secret keys, and their format types. You will explore PKI: its setting up and working, PAM authentication, and MTU troubleshooting. Next, client-server mode is discussed, the most commonly used deployment model, and you will learn about the two modes of operation using "tun" and "tap" devices. The book then progresses to more advanced concepts, such as deployment scenarios in tun devices which will include integration with back-end authentication, and securing your OpenVPN server using iptables, scripting, plugins, and using OpenVPN on mobile devices and networks. Finally, you will discover the strengths and weaknesses of the current OpenVPN implementation, understand the future directions of OpenVPN, and delve into the troubleshooting techniques for OpenVPN. By the end of the book, you will be able to build secure private networks across the internet and hostile networks with confidence.
Table of Contents (17 chapters)
Mastering OpenVPN
About the Authors
About the Reviewers

Three-way routing

As stated in the introduction, point-to-point networks are an excellent choice when connecting a small number of endpoints. In this example, we will show how to connect three sites together using point-to-point tunnels. It will also show how quickly the configuration of such a setup can become very complex.

Consider the following network layout:

We will create three tunnels between the sites and set up redundant routes. That way, if one of the tunnels goes down, all the sites will remain visible to each other. However, this is at the cost of a performance penalty. Let's assume that the link between site A and site B goes down. The backup route goes from site A to site C to site B, so now traffic from site A to site B has to make an extra hop.

First, we create three secret keys:

$ openvpn –-genkey –-secret AtoB.key
$ openvpn –-genkey –-secret AtoC.key
$ openvpn –-genkey –-secret BtoC.key

Then, we transfer these keys to all endpoints over a secure channel (for example, using...