Gigaset deskphones include the ability to build secure VoIP-Infrastructures via the OpenVPN Technology. Gigaset decided to use OpenVPN because it is compatible with SSL/RSA Certificates and X509 PKI, NAT, DHCP, and TUN/TAP virtual devices. OpenVPN is Open Source and is licensed under the GPL.
This article explains the step-by-step implementation of OpenVPN on Gigaset desktop phones, including server installation and setup, creating the phone configuration and applying it on the phone.
The OpenVPN server is available for free and there are various guides available on installing and configuring it. This section contains one out of several methods to install and set up a minimal OpenVPN server on Linux and Windows. For more options and detailed information, see https://openvpn.net or the available documentation for your server.
The VPN feature is not shipped with the default firmware due to security considerations. Gigaset provides the VPN feature in a small firmware patch which needs to be installed. This patch contains only the VPN feature and thus is very small in size.
To install the VPN feature patch follow one of the following procedures:

The phone will reboot and install the patch. Afterwards you will be able to use the VPN feature
It is also possible to install the VPN patch automatically via GRAPE, as part of the provisioning or even prior to the settings being fetched by the phone.
If the VPN installation was successful, the VPN feature will be available. Here is now you can check that the VPN feature is available:

