Last night I hacked around a bit with my Gallant 900mhz. As you may know there are 3 ethernet ports (2 via add-on PCI boards, 1 integrated into mobo) on this unit. All of them are based on the Realtek RT8139 chip and all can be used in Linux.
(I do not have a cel633 unit so I will have to let someone else post details on how many ethernet ports it has, whether they are all functional, etc. Any info you can provide is appreciated, I'm sure.)
I currently have my Gallant set up using eth0 for WAN, eth1 for Wired LAN, and eth2 for Wireless LAN. I could easily move the WLAN into the Wired segment off the same switch to free up eth2, and then remove eth2 altogether and put another PCI card in its place... but I have no reason for that currently so it will stay where it is. Argubably you could put a better sound card, scsi card, video card, firewire or usb2 card, etc in that spot provided the power supply does not get in the way if you were so inclined.
By default the Gallant is set up so that the "top" PCI card labelled WAN is eth0, the "bottom" pci card labelled LAN is eth1, and the covered up motherboard port is eth2. You could change this if you really wanted to, of course, but that is an advanced topic for now.
Use standard "ifconfig eth2" commands to set parameters for this port, or create the appropriate ifcfg-eth2 file in /etc/sysconfig/network-scripts. I have no idea if there is any way to configure eth2 via the Gallant Web interface, as I have not yet even bothered to look at it believe it or not. I suppose I will do that tonight.
Just wanted to let everyone know that just because the port is covered up by the ATX Backplate does not mean it does not function!
ps- I am going to get the (also covered up) Sound ports working tonight on this board, provided they are relatively standard and I can find drivers. I will post more details as I have them...