I have been recently watching https://www.youtube.com/watch?v=8zFQG5mKwPk&feature=autoshare . Regardless external bridge br-ex usually doesn’t have DHCP mode but on system where management and external interfaces are supported by different NICs ( say eth0 and eth1) . It makes sense to turn br-ex into DHCP mode, splitting DHCP pools of DHCP Server serving physical external network and allocation pool of floating IPs which belongs to virtual external network. Lars’s Kellogg Stedman Video has been made for RDO IceHouse, and I wanted to make sure that explicit update to ovsdb via br-ex syntax would work as expected on RDO Mitaka . To see for yourself that it works exactly as proposed a while ago.
Complete text may be seen here http://bderzhavets.blogspot.com/2016/06/rdo-mitaka-aio-setup-with-external.html