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

Using the tap device (bridging)

A special use case for a tap-based configuration is bridging. The term bridging applies to a feature of the operating system to bridge two network adapters together. When two (or more) adapters are bridged, all Ethernet traffic that is received on one of the adapters is forwarded out to all other adapters that are part of that bridge. This makes it possible to join (bridge) two network segments together and make it appear as if it is a single Ethernet broadcast domain. Common use cases for bridges are as follows:

  • The VPN clients need to be fully and transparently integrated into the server-side LAN. Note that the same effect can often be achieved using a proxy-arp setup.

  • Some older computer games only allow multiuser games when all computers are part of the same broadcast domain.

  • Some legacy network protocols, notably the original Microsoft NetBIOS (non-TCP/IP-based) protocol, do not work well across network routers, or even assume a fully "flat" network space...