Chapter 1. Troubleshooting Basics

Troubleshooting a failed server or client deployment can be a daunting task, particularly for a novice user. A vast number of users do not fall into the typical system administration role, and they are either hobbyists or just venturing into virtual networking and cryptography. By the end of this chapter, the tools' key to identifying and correcting problems will be illustrated, and their utility will be demonstrated.

The general concepts of troubleshooting apply not only to fixing a problematic OpenVPN client or server process but also to nearly everything encountered in day-to-day work. At its most basic level, the idea of divide and conquer is the phrase of the day. Separating components that are functional from those that are broken will quickly absolve the administrator from needless work and investigation.

The book is structured progressively, and it aims to help you find solutions quickly. This book will cover the following key topics surrounding fixing, identifying, and resolving OpenVPN problems:

• A troubleshooting toolkit is a key to gleaning all the data needed to focus on a problem and resolve it.
• Common OpenVPN issues are explored. Years of help supporting OpenVPN administrators on the forums and in IRC have provided a plethora of data, and the most common issues faced in the field are identified and solutions are provided.
• The OpenVPN installation on various operating systems is covered. The best client for each operating system is identified, including mobile device options. Where to go to obtain the installers and files needed.
• Log files are the primary source of troubleshooting data. When to use what verbosity level and how to search for the data within the log is explained.
• Startup and shutdown of the OpenVPN process for both the client and the server can cause stress and anguish. OpenVPN packaging is explained, where to go for help is shown, and how to troubleshoot those startup routines will be demonstrated.
• Routing and networking can be a difficult concept to comprehend. This is likely the number one area of difficulty for beginning OpenVPN administrators.
• We will discuss performance issues and how to correct performance-related issues. Also, cipher suite, key size, compression, and routing optimization will be illustrated.
• Finally, problems external to OpenVPN will be explored. Such things include local LAN address collisions and incorrect firewall filtering, both locally and at an ISP.