OpenVPN, by itself, can be a complex system, with given certificates, keys, configuration, scripts, hardware, and so on. The previous eight chapters of this book have touched on troubleshooting techniques and points on where to look within OpenVPN to address problems. However, once all the internal problems have been addressed, there are still several external influencers that can create additional hassles for your VPN.
Troubleshooting external factors for many things can be a difficult endeavor. In most cases, you'll be looking into a veritable black box for which you don't have a key. By setting up a VPN server, you are relying upon your Internet Service Provider (ISP) to allow transit for your VPN traffic on both the server and client side of the connection.