Routed KVM network with different subnets

Hello,

I've been bashing my brains out trying to figure this out. In my scenario, I have two machines connected to the public internet via Ethernet with a common VLAN, and each machine has a single public IP. (they also have a private ethernet VLAN but is a secondary concern)

Each machine is separately assigned an IP block which are totally both totally separate IP subnets, and also separate from the common subnet on the VLAN. The default gateway on the first network mentioned above is configured to accept traffic from these subnets.

My question is: how do I configure my machine so Cloudmin can automatically create virtual machines that use and draw from these different subnets? Remember, there are three subnets involved:

---common VLAN--- (common subnet)

---> Machine 1 ------>private subnet 1

---> Machine 2 ------>private subnet 2

I figured this out in Xen long ago, but now I want to use KVM instead. Any ideas anyone?