# Background
###### tags: `QVPN`

## Introduction
Users can use QVPN to create VPN connections with QNAP NAS, or indirectly from QNAP NAS to other VPN server/services.

## Notices
Before establishing a VPN connection, there are some notices:
1. Tier 1 VPN connection is established based on QBelt.
2. In current back-end settings, the Qbelt server IP is set as the IP of the default gateway, so the default gateway IP needs inputting in NAS profile. If users want to use other IP, they need to change the default gateway and re-enable QBelt server.
3. For all VPN types, the IP of tier1 and tier2 NAS should be different, or it will lead to IP conflict and abnormal behavior.

## The step to create VPN connection
Old flow:

1. Login to NAS via login module
2. After login successfully, it will check if VPN requisites are met or not via API.
3. If all requisites are met, start to send Qth connection request. (Qth library)

New flow:

1. Start to send Qth connection request. (Qth library)
2. After VPN connection is established, try to login NAS via login module if sid is null.

PS.
Because the QNAP login module is not integrated in the Nagarro release version, an interface(LoginController.java) is added to integrate the QNAP login module.
However, the interface is not completed. For login, an new server instance is created every time, and the necessary parameters are set to start login.