To extend the range of an SSID over a larger physical area, you can assign the same SSID to multiple AP devices. When a wireless user moves to a different location on your physical network, the wireless client can automatically connect to a different AP device that has a stronger signal for that SSID. This eliminates the need for users to manually reconnect when they move their wireless devices around your office. Simple roaming relies on the wireless client to switch between wireless access points.
For this deployment scenario, you can connect each AP device directly to a trusted XTM device interface, or to a switch on the trusted network. As long as you connect all AP devices to interfaces in the same network security zone, wireless clients that connect to the SSID can roam between the AP devices.
The diagram below shows three AP devices connected to the trusted network, two connected to a switch, and one connected to a trusted interface on the XTM device. All AP devices use the same SSID.
About AP Device Configuration
Configure AP Devices in the Gateway Wireless Controller