I have 12 computers in a workgroup, and three of my computers in this workgroup have separate Internet connections. Now I want share Internet Connection 1 to three computers, Internet Connection 2 to three computers and Internet Connection 3 to the remaining three computers within the workgroup -- as well as enable file sharing among all 12 computers. What IP should I be using to enable file sharing within the network? Which network device should I be using to do this?