How to get bytes sent/received only to the internet?

Hi, I'm a beginner in C#. One of my personal hobbies is writing a program that tracks bandwidth usage. I'd like to limit bandwidth to just traffic to and from the internet. So any local network traffic would be ignored. I know this could be done using WinPCap with a wrapper such as SharpPcap by filtering each packet. I would prefer not to have an extra install if at all possible. I have also looking into using WMI to retrieve packet information, but there doesn't seem to be a way to sort by Source or Destination Address. Any help would be appreciated, thanks!