I lose internet connection anytime i plug my macbook pro in with an ethernet cable, is there a reason?

[694]

Or an additional setting that im just missing that wont let me use ethernet?
Yes the router, its an xfinity router

[Adrian]

What are you plugging into? What router?

[Boris 24]

If you mean you loose wifi when you plug-in cable to router - then yes there is a reason.Two network adapters can't work on one computer at the same time.Wireless adapter temporary disables when you plug into router ethernet cable.When you unplug cable wireless adaptor starts working.