I use a wireless home network. I also want to use the same computer in another room using a wired connection on the same network

Question

I have an ATT UVerse gateway for internet and TV. I use two macbook pros on the wireless connection of this gateway. At times I want to be able to take one computer into a different room and connect to an eithernet connection which goes to the same gateway. Is it a simple feat or do I have to make preference changes each time I change connection type?