Book Image

Troubleshooting OpenVPN

By : Eric F Crist
Book Image

Troubleshooting OpenVPN

By: Eric F Crist

Overview of this book

OpenVPN, the most widely used open source VPN package, allows you to create a secure network across systems, keeping your private data secure. Connectivity and other issues are a pain to deal with, especially if they are impacting your business. This book will help you resolve the issues faced by OpenVPN users and teach the techniques on how to troubleshoot it like a true expert. This book is a one stop solution for troubleshooting any issue related to OpenVPN. We will start by introducing you to troubleshooting techniques such as Packet Sniffing, Log Parsing, and OpenSSL. You will see how to overcome operating system specific errors. Later on, you will get to know about network and routing errors by exploring the concepts of IPv4 and IPv6 networking issues. You will discover how to overcome these issues to improve the performance of your OpenVPN deployment. By the end of the book, you will know the best practices, tips, and tricks to ensure the smooth running of your OpenVPN.
Table of Contents (16 chapters)

Routing


OpenVPN provides powerful routing capabilities allowing the network administrator to direct traffic from clients where it needs to go. These routes can place entire subnets behind specific client connections, through other routers on the server side, or out to the Internet. There are two distinct zones when discussing routing and VPNs. I like to classify them as internal and external.

Regardless of which bucket your routes go into, it is vitally important to consider that both endpoints in the route need to know how to reach the other. There are varying techniques for accomplishing this: static routes, dynamic routes, NAT/PAT, and so on. Failure to ensure that there is a return path will prevent useful traffic from flowing.

In the following example image, the OpenVPN server resides behind a port-forwarding network gateway. The LAN gateway, nor the LAN file server, however, know how to route the 10.8.0.0/24 network. The OpenVPN client is able to send traffic via the OpenVPN server to...