If you are a member at Costco, they have an LED rope light for sale. It is about 20' long and is totally sealed. The last two RV's I have had, I zip tie it to the undercarriage using any attachment point I can find. Propane lines, skirting after drilling a small hole in it, etc. I then buy a cheap extension cord, cut the male plug end off, push the wire through an exact sized and drilled hole through a basement storage compartment that has a receptacle in it. Install a repair male plug on the cord and power the rope light. Most times I just let it plugged in as it only powers up when I am plugged in or genny running.
It is not bothered by the elements and draws around 15 amps.
Can't tell you if it keeps the pack rats away.