Okay, here's what I had to do, I had a similar problem, only my problem was, in my smoothwall machine I have a 10TX card in the slot for eth0 and a 10/100 card in the slot for eth1.
I wanted eth1 to be my public interface because the slower speed would not impact me on the internet, where it was a wildcard I didn't want on my internal network (I wanted all 10/100 interfaces on my network.)
Problem:
By default, smoothwall wants to configure the private interface first, and the public interface second, and of course it wants to use eth0 first.
What I had to do was, instead of having it probe for the first interface, I manually searched for the right driver for the chipset of the card (Did you check and make a note of the chipsets?)
I was fortunate enough, that I had 2 cards of different chipsets.
After I installed the drivers for eth1 while configuring my private (green) interface. I simply allowed it to probe for the other drivers and it installed them perfectly for the other interface.
I hope I explained that better than I think I did.
If that doesn't work for you you'll have to use the "route" command to change your routing tables using the MAC addresses for the cards.
I am about to have to try that so I can subnet my network and I don't even know if it can be done. But that is half the fun of being a newbie!
At least to me it is.
I am a
