Fortinet FortiGate 1U Quick Start Manual page 234

Edit the primary and secondary interfaces of
FortiGate 1.
Configuring security policies
on FortiGate 2
Go to Policy > Policy > Policy.
Create the four security policies required for
both FortiGate 2's primary and secondary
interfaces to connect to FortiGate 1's primary
and secondary interfaces.
214 The FortiGate Cookbook 5.0.