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

Routing and server-side routing

A VPN is only truly useful when the VPN clients have access to server-side resources. In order to access these resources, routing is needed in most cases. OpenVPN has many options to automatically set up and tear down extra routes whenever a client connects or disconnects.

It should be stated that most OpenVPN troubleshooting issues are related to routing. Setting up a VPN connection is one thing, getting network traffic to flow properly is another. This often has little to do with OpenVPN itself, but more with the routing tables and firewall rules on both client and server side.

The most common layout for accessing resources on the server-side network is depicted here:

The server-side LAN is The resources that the VPN clients need to access are located on this subnet. Thus, the server needs to instruct the VPN clients that an extra route needs to be set. This is done using a push option, where the route configuration is pushed to the client...