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

Chapter 6. Client/Server Mode with tap Devices

The other deployment model for OpenVPN is a single server with multiple remote clients capable of routing Ethernet traffic. We refer to this deployment model as client/server mode with tap devices.

The main difference between tun and tap mode is the type of adapter used. A tap adapter provides a full virtual Ethernet (layer 2) interface, whereas a tun adapter is seen as a point-to-point (layer 3) adapter by most operating systems. Computers connected using (virtual) Ethernet adapters can form a single broadcast domain, which is needed for certain applications. With point-to-point adapters, this is not possible. Also, note that not all operating systems support tap adapters. For example, both iOS and Android support tun devices only.

In this chapter, we start with a basic client/server setup, which is very similar to the basic setup described in Chapter 4, Client/Server Mode with tun Devices. However, there are subtle differences that will be discussed...