Why is dns a requirement for active directory to work?

DNS is extremely important to all aspects of proper Active Directory operation. Any time a client makes a request for a domain service, it must find a domain controller to service that request, which is where DNS comes in to play.

There are two types of DNS queries: recursive and iterative.

When a DNS client requests DNS information, it uses a recursive query to do so.

In a recursive query, the DNS client sends its query to the first DNS server that it has been configured for in its TCP/IP configuration. It then sits and waits for the server to return an answer. If the server returns a positive response, the client will then go to the IP address returned by the server.