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
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Understanding the client/server mode


The client/server mode was first introduced with OpenVPN 2.0. In this mode, the server is a single OpenVPN process to which multiple clients can connect. Each authenticated and authorized client is assigned an IP address from a pool of IP addresses that the OpenVPN server manages. Clients cannot communicate directly with one another. All traffic flows via the server, which has both advantages and disadvantages.

The advantages are as follows:

  • Control: The VPN server administrator can control which traffic is allowed to flow between clients. By default, no traffic is allowed to flow between clients. However, using either the OpenVPN option client-to-client or by using clever firewall and routing rules, it is possible to allow clients to communicate with each other.

  • Ease of deployment: It is much easier to set up a single server that can be reached by many different clients than it is to ensure connectivity between a multitude of clients, each with their own...