I finally figured out how to do that. Note that these steps bellow might not be accurate as I recall them out of my mind.

1. Make sure you have attached both your network cards. :)


2. Create network connections using Configure Your Computeer.
   Add both network cards. Just make sure they use different subnets.


3. Edit /etc/ifplugd/ifplugd.conf.
   Change the line
   
INTERFACES="eth0"

   to
   
INTERFACES="auto"

   

The last item is the most frustating thing because without it the client, especially if you use crossed UTP, will sometime behave strangely.
Enough for now. Next time perhaps I will show my dhcpd.conf.