hi guys, is it possible to use the LAN 2 port at the BTU? or does it need some setting up?

i plan to use 2 routers, 1 for 1st floor and the other for ground floor since thats where the set top box will and it seems the STB will only work on that port #4 on the standard router tm provided.

es i know there is so many stuffs that can be used to connect the set top box like the power line adapter etc but at the moment im stuck with using cables.