DNS queries

[Archibald]

Hi,

anyone out there know the difference between RECURSIVE and ITERATIVE DNS queries ?

[bossman]

@Archibald:

Recursive queries When a client system sends a recursive query to a local name server, that local name server must return the IP address for the friendly name entered, indicate that it can't find an address, or return an error saying that the requested address does not exist.

Name servers do not refer the client system requesting a recursive query to other DNS servers. When answering recursive queries, the originating client does not receive address information directly from any DNS server other than the local name server.

Typically, the local name server will first check DNS data from its own boot file, cache, database, or reverse lookup file. If the server is unsuccessful in obtaining the answer from those local sources, it may contact other DNS servers for assistance using iterative queries and then pass the information it receives back to the client that originated the name resolution request.

Iterative queries:
In iterative queries, name servers return the best information they have. Although a DNS server may not know the IP address for a given friendly name, it might know the IP address of another name server likely to have the IP address being sought, so it sends that information back. The response to an iterative query can be likened to a DNS server saying, "I don't have the IP address you seek, but the name server at 10.1.2.3 can tell you."



Read more: Difference between dns recursive and interactive query

[Archibald]

Thanks Bossman for such a rapid response !!! Makes a lot more sense now.