I (too) have the Gigabyte GA-7n400 PRO2, on which I have installed Mandrake 10. It is dual-booted with Windows XP.
The on-board Realtek RTL8169 works fine under Windows. However, I have had no success in Mandrake. I'm going to have a play around with it, and I'll let you know of a solution (if any).
Let me know of any success you have.