1. Instruction of Open VPN

OpenVPN is an open source software application that implements virtual private network (VPN) techniques for creating secure point-to-point or site-to-site connections in routed or bridged configurations and remote access facilities. It uses a custom security protocol that utilizes SSL/TLS for key exchange. It is capable of traversing network address translators (NATs) and firewalls.
If you open the VPN for the phone, the phone can access to the company's internal network, and register the accounts and make calls. For the server configuration please consult the server vendors.
For example: branch, dealers, partners and customers ,town on business personnel request register to internal sip server to more convenient access to network resources of enterprises ,the Open VPN meet with it.
Software source: openvpn-2.2.2.tar.gz
Configuration of OpenVPN Client:
Create client configuration for OpenVPN , please consult your OpenVPN Provider. And you can also refer to the template file provided by Htek.
VPN Config :

2. To configure VPN via Web

2.1 Login the phone's webpage and click Network?Advanced
2.2 Click button, and choose the configuration file.
For example: client.tar

2.3 Click .
2.4 Choose Yes to Active VPN:
2.5 Click to save the configuration and then a window pops up:

2.6 Click "OK" and then the IP Phone will reboot.
2.7 Then VPN address will display on Home—Status.

3. To Configure VPN via Phone LCD

Precondition:
You must import the config file via Web first: click Network?Advanced?choose file?import
3.1 Import the config file via web: refer to 2.1—2.3 Precondition
3.2 Press Menu?Setting?Advanced Setting (default password: admin)?Network?VPN
3.3 Set "VPN Active" to be "Enable", and press the "Save" button or OK key;
3.4 A Note pops up and then Press OK to Reboot the phone.

3.5 Then VPN address will display on Status (Press Network Button)