Nighthawk MR60 creates a separate LAN from my main modem router

I connected a Nighthawk MR60 mesh router to my cable modem router and it autoconfigured the local network IP as 172.16.0.1, whereas my modem router has a network IP of 192.168.0.1. This creates 2 LAN's that don't talk to each other (printer on one, wireless devices on another, etc.). Is there a way to configure the mesh router or modem router to be on the same LAN? Do I turn off "router mode" on the modem router? The mesh router is hard wired to the modem router.