Comment 8 for bug 1738420

The VM might be running a different dhcp client, so might be storing the information in a different location.

It looks like the external DHCP server is allocating addresses from a different subnet, so that looks Ok, and you need to have the neutron DHCP server running to service the VMs, I think you just need to find out why the VMs are getting a different IP from what neutron has allocated for them. Either finding the lease file or watching with tcpdump would help, once we have that we can figure out what needs to be fixed.