Chapter 11 IPsec VPN for FortiOS 5.0 : Protecting OSPF with IPsec : OSPF over IPsec configuration : Configuring static routing
  
Configuring static routing
You need to define the route for traffic leaving the external interface.
1. Go to Router > Static > Static Routes, select Create New.
2. For low-end FortiGate units, go to System > Network > Routing and select Create New.
3. Enter the following information.
Destination IP/Mask
Leave as 0.0.0.0 0.0.0.0.
Device
Select the external interface.
Gateway
Enter the IP address of the next hop router.