Chapter 11 IPsec VPN for FortiOS 5.0 : L2TP and IPsec (Microsoft VPN)
  
L2TP and IPsec (Microsoft VPN)
This section describes how to set up a VPN that is compatible with the Microsoft Windows native VPN, which is Layer 2 Tunneling Protocol (L2TP) with IPsec encryption.
The following topics are included in this section:
Overview
Assumptions
Configuring the FortiGate unit
Configuring the Windows PC
Troubleshooting