Comment 1 for bug 1849690

Publishing DNS records for ports only happens under certain conditions, please have a look at https://docs.openstack.org/neutron/latest/admin/config-dns-int-ext-serv.html#configuration-of-the-externally-accessible-network-for-use-case-3 and verify that your setup meets these conditions.

There is also an extension being worked on that will allow users to override these conditions, see https://launchpad.net/bugs/1784879 for that.