Comment 2 for bug 1650678

The bug suggests that dns_domain is being used in for tagging purposes. Ports and floating ips dns_name and dns_domain attributes have consequences: if an external DNS service is configured, Neutron is going to try to set up the dns_name in the dns_domain in the external DNS service. Furthermore, the zone indicated by dns_domain is expected to exist in the external DNS service.

If the purpose is only tagging, please consider the Neutron tags extension, which was created exactly with this in mind: http://docs.openstack.org/newton/networking-guide/ops-resource-tags.html. Although in its present form it only applies to networks right now, work is under way to extend it to other resources, including ports: https://review.openstack.org/#/c/413662/