Recursive Servers basic question in DNS
 

Newbie
i know recursive servers are servers that query's untill they get the answer to original
question.

but what is the actuall use of it

what recursive yes/no;

any example for this that will help me to understand the concept.

A DNS server that has recursion=yes; will return the answer to any query by following the delegation path from the root name servers to the authoritative DNS server for that domain name.

A DNS server that has recursion=no; will NOT return an answer, but simply a list of the root name servers; which as far as its concerned are authoritative. i.e. Any answer to this query would have to start at the root name servers.

A typical use for recursion=no is to stop someone on the internet from using your server as their DNS server.

Example: Using my XP box and nslookup, query my DNS Server (recursion=yes) running on my FC2 system.Now change nslookup to use another DNS server which has recursion=no configured.
Note that the DNS server ns4.myisp.net did not return an answer section, but a list of the root name servers (served by). So any host configured to use the above name server would get a "Name not Found" type of error to any query for which this DNS server is not authoritative.