Iterative queries are the easiest to understand. A client asks the DNS server for an answer, and the server returns the best answer. This information likely comes from the server's cache. The server never sends out an additional query in response to an iterative query. If the server doesn't know the answer, it may direct the client to another server through a referral.

In a recursive query, the client sends a query to a name server, asking it to respond either with the requested answer or with an error message. The error states one of two things:
>> The server can't come up with the right answer.
>> The domain name doesn't exist.
In a recursive query, the name server isn't allowed to just refer the client to some other name server.
Most resolvers use recursive queries. In addition, if the DNS server uses a forwarder, the requests sent by the server to the forwarder will be recursive queries.

Inverse queries uses PTR records. Instead of supplying a name and then asking for an IP address, the client first provides the IP address and then asks for the name. Because there's no direct correlation in the DNS namespace between a domain name and its associated IP address, this search uses in-addr.arpadomain. Nodes in the in-addr.arpa domain are named after the numbers in the dotted-octet representation of IP addresses.

But because IP addresses get more specific from left to right and domain names get less specific from left to right, the order of IP address octets must be reversed when building the in-addr.arpa tree. With this arrangement, administration of the lower limbs of the DNS in-addr.arpatree can be given to companies as they are assigned their Class A, B, or C subnet addresses or delegated even further down thanks to variable-length subnet masking.

Name servers are acting as resolvers, are allowed to cache all the received information, during this process each record contains information called time to live (TTL).

The TTL specifies how long the record will be held in the local cache until it must be resolved again. If a query comes in that can be satisfied by this cached data, the TTL that's returned with it equals the current amount of time left before the data is flushed.

• The Domain structure.
• The Domain Name .
• storage location of the database and log file.
• Location of the shared system volume folder.
• DNS config Method.
• DNS configuration.