Fortigate 80C : Multiple Subnets Routing

Hi guys,

I have a Fortigate 80C. I currently have a subnet but would like to restructure.

My goal is to create a new one and reconfigure devices gradually.

e.g.

Current Subnet : 192.168.1.0/255.255.255.0

New Subnet : 192.168.2.0/255.255.255.0

I need the 2 subnets to be able to communicate with each other.

I don't have a VLAN switch.

I tried to create a secondary ip address on internal interface but it didn't work.

Is the VLAN route the good way ?

Thanks,

Maxime