Chapter 10 Install and System Administration for FortiOS 5.0 : PPTP and L2TP : Adding the security policy : Testing L2TP VPN connections
  
Testing L2TP VPN connections
To confirm that a VPN between a local network and a dialup client has been configured correctly, at the dialup client, issue a ping command to test the connection to the local network. The VPN tunnel initializes when the dialup client attempts to connect.
See Also
Configuring a Linux client
Monitoring L2TP sessions
Logging L2TP VPN events
Adding the security policy
PPTP and L2TP