OVN DNS entries in the northbound database of RHOSP may interfere with customer's data-center DNS solution

Issue

OVN has a built-in DNS server for assigning names to logical switch ports within an OVN logical network. When the RHOSP Networking service (Neutron) creates a VM's ports, it uses the built-in DNS server to add corresponding DNS data to the OVN north bound database. The DNS data is translated into logical flows in the southbound layer. As a result, ovn-controller can resolve DNS requests locally. The requests never leave the hypervisors.

Customers who use external DNS tools to handle VM DNS requests should consider disabling the built-in DNS feature.