OpenVPN is arguably the best cross-platform secure networking technology currently available. The development community is large and active every day of the year, with new developers popping up regularly with patches and feature requests. It is not only used by hobbyists, but also by for-pay VPN providers strewn about the Internet.
In Troubleshooting OpenVPN, we identify the most common problems and pitfalls in the deployment of OpenVPN. We demonstrate where and how to use an assortment of diagnostic and investigative tools, both common and lesser known.
By the end of this book, you should be able to understand and identify where a problem resides, both within your VPN infrastructure and also from external causes. The log file is fully detailed and you will be able to leverage the varying logging levels to suit your troubleshooting efforts.
Chapter 1, Troubleshooting Basics, helps the reader break down problems into digestible portions with related components. Some of the concepts discussed include generic techniques useful in more than just OpenVPN problem solving.
Chapter 2, Common Problems, will identify the issues seen most frequently by both novice administrators and experienced administrators alike.
Chapter 3, Installing OpenVPN, covers compilation and installation of OpenVPN on a variety of platforms. Virtual network adapters, alternative client packages, and software dependencies will be identified.
Chapter 4, The Log File, focuses heavily on the OpenVPN log file and how to adjust and decipher the verbosity of the available messages. This is an extremely valuable resource when identifying and correcting problems.
Chapter 5, Client and Server Startup, discusses software and system dependencies necessary for process startup. Items like file permissions, scripting, and basic networking all contribute to successfully running OpenVPN.
Chapter 6, Certificates and Authentication, illustrates the varying authentication paths and where breakage can occur. System time, authentication backends and scripting are all addressed.
Chapter 7, Network and Routing, shows where network topology and routing bring complexity to the OpenVPN architecture. Conflicting routes, address inconsistency, and subnetting will all be covered.
Chapter 8, Performance, was written to help you identify performance bottlenecks and places where efficiencies can be improved.
Chapter 9, External Problems, covers where and when problems can exist outside your OpenVPN infrastructure, and even entirely outside your network or control.
This book was written with the VPN administrator in mind. Many of the examples within leverage both the server and client sides of a connection, and lack of control at the server end will prove frustrating. I am assuming you either have access to a server, or have the means to create a functioning server, with your operating system of choice.
Examples within this book are focused primarily on Linux or BSD command-line tools, but there are a number of Windows examples interspersed within the content. To make the most of your time, try to have the following available:
An OpenVPN server, ideally running on Linux or FreeBSD
An OpenVPN client, running any operating system you choose
The ability to install software on and connect to the OpenVPN server without OpenVPN running
An OpenVPN server administrator is most likely to use this book to its potential. Enterprising VPN users may also be able to use the techniques and applications described within to their own benefit, however. Much of this title covers basic troubleshooting skills that can be leveraged in nearly any situation, not just with OpenVPN.
In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.
Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "The --auth-user-pass-verify script is the last in a long chain of scripts that are run."
Any command-line input or output is written as follows:
author@example:~-> sudo openssl s_server -key key.pem –cert cert.pem -WWW -accept 443
New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "By going to Preferences | Protocols | SSL, Wireshark provides a way to import the TLS key we created earlier."
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