IPSec VPN: Authentication by pre-shared key
You wish to securely link up two sites on your company network currently linked via the Internet. To do so, you need to create a site-to-site IPSec VPN (also known as "gateway to gateway").
The authentication method presented in this tutorial is based on the use of pre-shared keys (authentication by certificate can also be set up).
This document describes the VPN configuration to create, so that you can allow a client workstation on the remote site to access an intranet server on the main site through this tunnel in HTTP.