First thing to check is whether the machine can see the network hardware. Unless you've seen the NIC workingwith another OS there may be a probelm with the board and it may not be functional at the hardware level. (Or maybe for an onboard card it could be disabled in the BIOS.)

In a terminal window try running

lspci | grep Ether

eg.

# lspci | grep Ether
0b:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM5709 Gigabit Ethernet (rev 20)
0b:00.1 Ethernet controller: Broadcom Corporation NetXtreme II BCM5709 Gigabit Ethernet (rev 20)

You can get more information about the NIC model to make it easier to search for support with a variation on the lspci command.

eg.

# lspci -vm -s 0b:00.0
Device: 0b:00.0
Class: Ethernet controller
Vendor: Broadcom Corporation
Device: NetXtreme II BCM5709 Gigabit Ethernet
SVendor: IBM
SDevice: Device 03a9
Rev: 20

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