Well I tried that. I mean ipaddress, subnet mask and gateway is not something very complicated to feed. But as soon as I added something that was dependent on shorewall, for ex. squid or firewall to be able to activate mac filtering fort the clients, the above problems arose and shorewall service was not able to start anymore, and I was not able to fix that with only one nic. Thats when I thought about the above solution which worked for me.