From a command prompt:
This should start up the configuration wizard.
You will need:
Gateway address: (local IP for your cable modem or router)
Machine address (IP for linux box)
OR, if your modem / router does DHCP, use it to automagically discover / assign addresses
Your Linux box doesn't know or care about the cable modem, it just knows whatever it blows out of the ethernet card goes to the internet, anything beyond that doesn't matter.