Im kind of wondering the same thing here. I know the manual specifically says 'directly attached devices' - so I'd like to know technically what this means as most devices with not, physically, be directly attached to ones Fortigate, that makes no sense.
From my setup I get a full device inventory when a subnets gateway exists on the Fortigate device. Additionally like you, when I have a static route from my CORE switch to the Fortigate - all I get is one device and the VLAN's mac address registers in the Fortigate.
So is the point of difference> Directly connected, as stated in the admin guide, means having the gateway on the Fortigate?
I'd really like to know this, as on my CORE I have 30+ VLANS. Then I route all of them out to the internet via a single vlan. I dont want to have to remove the route and have 30+ gateways configured on the Fortigate. But ideally I want full inventory list.
Any one an expert in this? How is anyone in similar setups getting full device inventory when your subnets gateway is NOT on the Fortigate?
Thanks so much.