[libvirt-users] basic network setup

I am setting up a network with 2 guests, each on different subnets. The physical machine has 2 NICS, one on each subnet. I want the physical and guest machines to have IP addresses with no NAT, in their respective subnets, and then I want a separate subnet where the 2 guests can connect directly to each other. Can somebody explain conceptually the best way to use physical adapters, bridges, virtual bridges, virtual networks to accomplish this.