[BigV]

I have done work like this for years. It's easy. I'd say make a surface mount block (I'd use a two jack box) sometimes called a biscuit block. These can be had for a couple bucks. I'd look for one that can be installed without tools. You take the wire, cut back the jacket, and fan out the individual conductors and nestle them into the color coordinated slots on the jack. Then you press down this little cap onto the backs of the wires and it pushes the wire down into a V with little blades that cut through the insulation to make the electrical contact. The cap clicks down and you're done.

Then I'd take that biscuit and mount it on the underside of your trailer whereever you can have easy access. /this is like installing an external jack/power outlet/ etc. Put it somewhere you can get to it, and that is protected from travel injuries. Any damn kind of weather box is fine.

The wires leading out of the jack/box will go through a hole in the floor like tw described and then up into your living space. Be generous with the cable, you can run it inside to whereever is another convenient space for your interior access. I would then terminate the inside end of the wires with another duplex rj45 surface mount block. The idea is that you'll have a "permanent" installation with female jacks on each end of a (pair of) cables that you never have to move ever. Cables that don't get moved dont' get worn or broken.

You'll then use regular patch cables with rj45 plugs on each end to go from jack to jack everywhere. From the house to the jack on the RV. From the interior jack to the interior switch. from the jack on the switch to the device. Don't make a cable that has a jack on one end and a plug on the other, you're begging for trouble there.

If you need help finding part numbers for these doodads, let me know.