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

Enabling client-to-client traffic

When multiple Virtual Private Network (VPN) clients are connected to the server, they are not permitted to exchange traffic. This is true for both tap mode and tun mode. In order to enable client-to-client traffic, there are two options:

  • Use the configuration option client-to-client. This allows OpenVPN to handle client-to-client traffic internally, bypassing the system routing tables as well as the system firewall/iptables rules.

  • Use the system routing tables and firewall/iptables rules to send traffic from one client to another and back.

The first option is the fastest option, both in terms of configuration and in terms of performance. If there are no restrictions on the traffic between VPN clients, add the line client-to-client to the configuration file tap-udp-server.conf, save it as movpn-06-01-server.conf, and restart the OpenVPN server using this configuration file:

$ openvpn --config movpn-06-01-server.conf

Reconnect the VPN clients. The first client...