Sharing internet connection

Hello all,

Recently took a dive into Unix using Fedora 12 atm. I have cable modem with DHCP and a linksys 8 port router. With windows I was able to simple use the uplink port and plug each computer into the switch and use the internet connection. Having no luck doing the same in Unix. I have 4 boxes which I want to set up an intranet but have internet capability on each box. My main box has 2 ethernet cards. At this point I simply would like to know how to connect my main box to the switch and use the uplink on the switch to obtain internet connect. On a side note I would like to also have a nic card with a decticated ip for the new intranet. Any suggestion or help would greatly appreciated. Thank you