I use a laptop, and have only just been able to finally connect an ethernet cable to it. However, ethernet doesn't work on Linux, returning this "Cable Unplugged" message, whereas it does work on dual-booted Windows.
I tried running "lspci -v" to get a list of where my drivers were located, but I could not find any entry for "Ethernet controller," or something of the like. That being said, I'm assuming I just don't have an Ethernet driver?? and I was wondering how I get one :)
It's probably a missing driver. You can boot into a live environment with Linux and download the driver from there if it recognizes it.
If it's a fresh install it might be simpler to reinstall and make sure to check the box that allows for proprietary drivers to be installed if necessary.
You can also find out the model of your network card and then download the driver package on another PC and move it over on a flash drive.