nslookup is a debugging tool provided with Windows NT 4.0. It allows anyone to directly query a name server and retrieve any of the information known to the DNS system. It is helpful for determining if the server is running correctly and is properly configured, or for querying for information provided by remote servers.
nslookup is used in the Windows NT command window to resolve queries either interactively or directly from the command line. Below is a command-line example of using nslookup to query for the IP address of a host:
nslookup www.fnc.govServer: thoth.ttgnet.com Address: 172.16.12.1 Non-authoritative answer: Name: www.fnc.gov Address: 126.96.36.199
Here, a user asks nslookup to
provide the address of
www.fnc.gov. nslookup displays the name and address of the
server used to resolve the query, and then it displays the answer to
the query. Notice the “Non-authoritative” message in the
response. thoth.ttgnet.com is our local server.
This messages tells us that the local server retrieved this answer
from its cache. As we’ll see shortly, when you need to do so,
nslookup allows you to go directly
to the remote authoritative server for an answer.
The real power of nslookup is seen in interactive mode. To enter interactive mode, type nslookup on the command line without any arguments. Terminate an interactive session by entering Control-C (^C) or the exit command at the nslookup prompt. Redone in an interactive session, the query shown earlier is: