Fortinet fortigate-100a Benutzerhandbuch

To route packets from Network_1 to Network_2, Router_1 must be configured to use 
the FortiGate internal interface as its default gateway. On the FortiGate unit, you 

would create a new static route with these settings:

Destination IP/mask: 192.168.30.0/24
Gateway: 192.168.10.2
Device: dmz
Distance: 10

To route packets from Network_2 to Network_1, Router_2 must be configured to use 
the FortiGate dmz interface as its default gateway. On the FortiGate unit, you would 

create a new static route with these settings:

Destination IP/mask: 192.168.20.0/24
Gateway: 192.168.10.1
Device: internal
Distance: 10