The modem has multiple outlets but I don't want to lay two hdmi cables the length of the hallway. I'm looking to split the signal at the entertainment center, not in the room the modem is in.
buster: You need a ROUTER behind the modem unless the modem is a router/modem combination unit. Switches will NOT WORK as they can not provide the needed IP addresses for more than ONE local unit.
You can not run more than one device from a modem. You need a router.
You buy a new modem with multiple network outputs, or you buy a network switch. Either way – time to go shopping.
You don't. You need a router.