I have two physical hosts which run debian lenny with kvm. They have one nic which connects to the internet and another nic which is a cross-link to each other, for a faster private net. On this kvm hosts run different guest hosts. Each guest has one public ip and one private ip.
The guests should be movable (migration) between the kvm hosts and keep their private ip address. I want to have something like a private Isolated network but it should span multiple physical kvm hosts. How Can I archive this? Is this possible? VPN? Bridge? Point-to-Point? I have no clue!
I don't think you need to implement anything special here. You just need create your guests with two interfaces, and bridge them to the private and public interfaces of the hosts. So long as the interfaces on the hosts are named and mapped the same way, your guests should retain the same public and private IPs on the same networks when they are migrated.