a cable modem, adsl, direcpc and other forms of dedicated connection
You must have two network cards installed on the PPPshar computer for all dedicated connections. (also see exceptions below)
Note : Do not connect your cable modem directly into a hub. Your cable modem should be connected to the pppshar computer and so you need two network cards in the gateway machine. By this setup your entire network will be on a physically separate network from that of your cable ISP, otherwise your network becomes very insecure. You'll probably have to use a cross-over cable instead of the standard one to make the connection from the modem to the card.
Exception 1 : External cable or DSL modems connected via USB - If you have to cable, adsl or satellite connection through a USB modem, then a second card is not required on the PPPshar computer to share the connection. Only one Ethernet card is needed to connect to the LAN, but since the cable / DSL modem is connected via USB, you don't need a second NIC. Just connect the network card to your hub and configure the tcp/ip for this card as per instructions in PPPshar Help document.
Exception 2 : Internal cable or DSL modems - Since the modem connects directly to your computer's internal bus (usually via a PCI slot), you don't need a NIC to connect to it. Just one NIC (or phoneline or wireless or powerline network card) in the pppshar machine is needed to connect to the LAN.
Exception 3 : External cable or DSL modems with wireless, phoneline or powerline-based LAN - In this case, one Ethernet card is needed to connect to the cable/DSL modem, but since your LAN is not Ethernet based, you don't need a second NIC.