I currently have a DSL connection on my Linux box that a few Windows PC's connect through to get on Internet. I would like to add a second cable connection from another company, with the intent that if the DSL goes down it will automagically bump to the cable connection and the PC's would stlil be able to get online. I've been googling and haven't really found a way to do this yet.
It can be either both connections going at the same time or one is off and one is on, with the states switching if one goes offline.
Currently, I am using Firestarter to setup the Internet connection sharing on the Linux box with my DSL. I'm using Fedora 6. I have three LAN connections on my box (one on-board, used for the LAN, two PCI NICs, one for the active DSL and one for the Cable I hope to be using soon!).