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

Client-specific configuration – CCD files

In a setup where a single server can handle many clients, it is sometimes necessary to set per-client options that overrule the global options, or to add extra options to a particular client. The option client-config-dir is very useful for this. It allows the VPN administrator to assign a specific IP address to a client, in order to push specific options such as a DNS server to a particular client or to temporarily disable a client altogether. This option is also vital if you want to route a subnet from the client side to the server side, as we will see later on.

A client-config-dir or CCD file can contain the following options:

  • push: This is useful for pushing DNS and WINS servers, routes, and so on

  • push-reset: This is useful to overrule global push options

  • iroute: This is useful for routing IPv4 client subnets to the server

  • iroute-ipv6: This is useful for routing IPv6 client subnets to the server

  • ifconfig-push: This is useful for assigning a specific...