On board ethernet.
Currently that rig is (6) AMD 6800’s, on risers, dual ATX power supplies.
If you are trying to get it configured, set it up with (1) GPU fully, then reboot with your target group of cards. Plan for trouble over (4) GPUs due to PCI mapping issues.
I disabled everything(and I mean everything) except USB, LAN, and ironically the iGPU(silly because I have not had a monitor on this one since summer?).