First I'd suggest you go to:
and check if your hardware (you NIC) is supported. It probably is.
Then I'd suggest you check what modules are loaded into your memory. You do that by running "lsmod|more" as root. Look for anything which might be your NIC.
I wouldn't be surprised if Red Hat had som kind of program where you can configure your hardware (like "harddrake" in Mandrake). If you don't find that kind of program you will probably have to recompile your kernel and then import the modules in memory.