Description of problem:

Customer needs to move lots of vms during maintenance periods from one cluster to another.  However since the customer is using provider vlan networks they can not keep the same ip. Different clusters have different allocation pools, there is concern of duplicate ips, dhcp leases etc, wrong dhcp server responding etc.

We might be able to use something like external dhcp between clusters, share same vlan ip range?   however they are still worried about potential problems. It's worth pointing out the customer is currently using OVS , however they would move to OVN in the future.  So we would need a solution that works in ovs and can withstand an ovn migration.  We are looking for a well documented solution , I'm aware of os-migrate,however that seems to use tenant networks, so wouldn't work here. The customer is able to do this in vmware and see's this as a lack of usability for Openstack.