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Understanding DNS, part 2

Workstations using a DNS server to locate resources on TCP/IP networks use three types of name queries: recursive, iterative, and reverse (sometimes called inverse). Knowing the differences between these query types can be helpful to your planning and troubleshooting efforts.

A recursive query is a query in which the DNS server will either provide a name for IP address mapping or return an error message to the DNS client. It can't refer the client to another DNS server. With an iterative query, the DNS server will give a match if it has one, but if it doesn't, it will refer the client to another DNS server that might. This is the typical query between a DNS client and server. A reverse name query is done when the IP address is known but the name of the host associated with that IP address is unknown.

Many times DNS name resolution involves all three types of queries. Understanding them can improve your ability to troubleshoot slow connections as well as help you determine DNS server placement in large networks.