Hi,
There are 2 modes supported now - Private network mode and router mode.
The WiFi router mode on the Instant On APs is meant to be used when the customer does not have a pre-existing gatway between the AP and the internet.
The Router AP will provide IP addresses to all other APs in the site. If the AP is AP11D, it will also provide IPs to the wired clients connected. You can also change the DHCP scope of the internal network of the AP in router mode.
You should make sure that when you enable this mode, there is no other router in the network for the clients and only one AP is created as a router in the site.