Q. I have VMs running in Azure that are joined to the domain but the DNS suffix is sometimes reddog. Is this a problem?
A. VMs in a virtual network always use DHCP and can be configured with specific DNS servers however the DNS suffix by default will be reddog.microsoft.com which is also the connection-specific DNS suffix for the ethernet adapter. When a VM joins an AD domain however the primary DNS suffix will automatically be changed for the IP configuration to that of the AD domain which overrides others and the adapter DNS suffix ignored. Therefore even through you see reddog.microsoft.com as the DNS suffix for the adapter as long as the IP configuration primary suffix is that of the domain there is no further action needed. This also applies to the domain controllers themselves if hosted in Azure.