The external DNS servers provide name resolution and mail exchange resolution for Internet users. Internal servers (such as the Active Directory and backup and restore servers) may not use the external DNS because of network restrictions in place.
The internal DNS servers, which should be installed on all of the Active Directory servers, provide name and service resolution for the computers on the back network. As part of the infrastructure, Active Directory requires a properly configured and functioning DNS. The best way to achieve this is to run DNS in Active Directory-integrated mode and allow registrations to be made automatically for computers which are members of the domain.
Internal DNS Requirements
The internal DNS is largely self-maintaining. Active Directory requires DNS; it is easiest to simply allow Active Directory to install and configure DNS during promotion of the Domain Controller. All of the appropriate service location records are created automatically, so any servers that you add to your network will automatically register themselves in the DNS.
External DNS Requirements
The requirement is simple: you need DNS servers, accessible from the Internet, that resolve Web server names to IP addresses and provide address resolution for queries coming from the internal network.
Each new customer you add to the service requires a registered Internet domain name. Therefore, for each new customer you add to the service you will need to add one or more "A" record(s) resolving the customer's hosted services to the external IP address(es) of the server hosting the service.
The external servers will need to be able to resolve names on the Internet so that outbound e-mail can be delivered. The DNS server will need to forward queries to some other DNS server or be able to contact the root name server.
You likely already have an external DNS server, so all you need to do is add the appropriate record(s). If you do not already have an external DNS infrastructure, then you need to build one.
For information on how to build external DNS servers, see Related topic Install and Configure the External DNS Server
Before you run your centralized management platform in a production environment you should build it on an isolated network to ensure that you have completed all installation and configuration tasks effectively and the infrastructure fits your needs. In particular, you should ensure that any integration with your provisioning system functions correctly, and that group policies work as intended.