This link should have the information you are looking for.
http://www.redhat.com/docs/manuals/l...de/ch-ppp.html
This is off of the main Redhat Linux 9 manuals page:
http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/
It's pretty sweet on DSL anyway with Bellsouth.net. I was used to running Linux servers when I first did a RH 7 or higher Internet connection for my DSL desktop at home. Ethernet is a breeze as well. Cable Modem uses the same Ethernet setup, as this page says the following:
Cable Modem Connection
A cable modem connection uses the same coaxial cable that your TV cable travels on to transmit data. Most cable Internet providers require you to install an Ethernet card in your computer that connects to the cable modem. Then, the cable modem connects to the coaxial cable. The Ethernet card is usually required to be configured for DHCP. To configure this type of connection, start Internet Configuration Wizard, select Ethernet Connection, and select DHCP on the Configure Network Settings screen.