Are you sure your network card isn't being detected?
Its possible RH didnt try to use DHCP if thats what your using. To check, go to Redhat Menu->System Settings->Network.
Then click 'eth0', click Edit on the top toolbar, and make sure 'Automatically detect settings with:' is set to DHCP. Then click OK, then do File->Save. Now click 'Deactivate' and then 'Activate', and see if it works.
If there is no eth0 at all, then go to the Hardware tab. You should see your network card. If not, your right, it wasnt detected.
Now copying drivers isn't necessary, because knoppix and rh have the same driver base (give or take). they both use the linux kernel which comes with drivers for almost all network cards.
Tell me what model card you have and I'll tell you what driver to load.