connecting to internet socket

i bought my nighthawk RAX200 but seems i maybe being silly. i had a nighthawk xs4 router before which connected straight to the wall socket for the Internet connection but when i replaced it with the RAX200 it has no Internet. now after spending way to many hours tring to figure out why it wouldn't connect, searching the net and reading the instructions many times it seems it has to run through a modem first. i setup my XS4 to run as a modem only and connected my RAX200 to which it now has internet and works just fine. Am i correct in thinking it doesn't have the modem built in and this is my only way of connecting it to have Internet.