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

Redirecting the default gateway

A very common use of a VPN is to route all the traffic over a secure tunnel. This allows one to safely access a network, or even the Internet itself, from within a hostile environment (for example, a poorly protected Internet cafe).

Redirecting the default gateway is achieved by adding the line push “redirect-gateway [def1 local bypass-dhcp bypass-dns]” to the server configuration file.

The parameters to redirect-gateway listed previously are optional, but they can play a very important role:

  • No parameters added: In this case, OpenVPN will replace the existing default gateway ( with the address of the OpenVPN server itself. An extra route to the OpenVPN server itself is also added so that the OpenVPN traffic itself is sent directly to the server, instead of via the tunnel. The disadvantage is that if the OpenVPN connection is stopped or breaks down, the original default gateway is lost. This usually causes a full loss of network connectivity.

  • Parameter...