You may need to turn off the router and start it up again to reset it before starting the computer in a different OS. I'm not sure. I'm trying to determine this for myself.
When I was working on my old PC and my new Mac Pro, I noticed that if I just took the ethernet cable from the Mac or PC and connected it to the other machine, it couldn't find the internet unless I turned off the router, waited a moment and turned it back on again, connected to the other machine and then started the machine.