Explanation: Box 1: No Only private AZ DNS Zones can use auto registration. The set DNS search suffix in the client changes nothing. Box 2: Yes vnet1 is linked and auto-rego is enabled, records get added automatically. Box 3: Yes vnet1 is linked and auto-rego is enabled, records get added automatically. Reference: https://docs.microsoft.com/en-us/azure/dns/private-dns-autoregistration