I originally had my Linux computer running on RedHat 9, this is half-bridged to my ADSL Modem such that eth0 has the actual external IP, eth1 was then connected to the internal network 10.0.0.x, and the internal network accessed the internet via the Linux computer using 'route'

However I recently decided to reformat the Linux computer and install Fedora Core 4, the same setup has not worked. Any suggestions on how to fix this? Feel free to change the IP information for both networks, just so that
External IP : eth0
Internal Network : eth1 and that the Internal Network can access the internet via eth0.

what does your iptables config look like?