Specify a static route on BGW320-500 to attached router?
I am using a BGW320-500 as my ONT and Wifi AP, and its LAN network is 192.168.1.x. I have another router attached to its Ethernet port, which is assigned a fixed LAN address (192.168.1.200) manages another subnet (10.100.0.x). On the BGW320-500, I need to ensure all LAN traffic destined to 10.100.0.x is provided to the the attached router at 192.168.1.200.
The only pertinent setting I see is a cascaded router settings, but for some reason it doesn't allow me to specify a 10.x.x.x/8 subnet for the cascaded network. Am I on the right track? How can I accomplish this setup without passing all traffic through the external router? Note I cannot change the network managed by the attached router, it must be 10.100.0.x.