Integrating smart phones into an existing VPN setup

OpenVPN on smart phones can only be used as a VPN client, which is the normal usage mode of smart phone anyways. For Android, multiple OpenVPN client apps exist. There are some subtle differences between the different apps, but all of them support only tun-mode setups, as the underlying OS does not support tap devices.

The question of which app to use on Android devices is a difficult one. If you are using a mix of iOS and Android devices then the OpenVPN Connect app is an easier choice, as the user interface is more consistent across the devices. If you use the commercial OpenVPN Access Server, OpenVPN Connect is the only route due to dynamic configuration and some server option differences. If you need some of the special features of the OpenVPN for Android app or if you want to use OpenVPN on non-ARM based phones or tablets, then OpenVPN for Android is the logical choice.

As can be seen from the previous example, some changes are required...