VIO offers 2 networking options via Neutron. Basic L2 networking with Neutron VDS plugin. Complete L2-L7 networking with Neutron NSXv plugin.
1. When using VDS plugin, DHCP VMs are created that manage the IP.
2. When using NSX, NSX edge VMs deliver DHCP.
If you don't mind sharing the name of your VMware sales/SE rep, then I can help connect you with more resources that can help with your OpenStack efforts.