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Nslookup

Displays information that you can use to diagnose Domain Name System (DNS) infrastructure. Before using this tool, you should be familiar with how DNS works. The Nslookup command-line tool is available only if you have installed the TCP/IP protocol.

Syntax

nslookup [-SubCommand ...] [{ComputerToFind| [-Server]}]

Parameters

- SubCommand ...   : Specifies one or more nslookup subcommands as a command-line option. For a list of subcommands, see Related Topics.

ComputerToFind   : Looks up information for ComputerToFind using the current default DNS name server, if no other server is specified. To look up a computer not in the current DNS domain, append a period to the name.

- Server   : Specifies to use this server as the DNS name server. If you omit -Server, the default DNS name server is used.

{ help | ? } : Displays a short summary of nslookup subcommands.

Remarks

  • If ComputerToFind is an IP address and the query is for an A or PTR resource record type, the name of the computer is returned. If ComputerToFind is a name and does not have a trailing period, the default DNS domain name is appended to the name. This behavior depends on the state of the following set subcommands: domain, srchlist, defname, and search.

  • If you type a hyphen (-) instead of ComputerToFind, the command prompt changes to nslookup interactive mode.

  • The command-line length must be less than 256 characters.

  • Nslookup has two modes: interactive and noninteractive.

    If you need to look up only a single piece of data, use noninteractive mode. For the first parameter, type the name or IP address of the computer that you want to look up. For the second parameter, type the name or IP address of a DNS name server. If you omit the second argument, nslookup uses the default DNS name server.

    If you need to look up more than one piece of data, you can use interactive mode. Type a hyphen (-) for the first parameter and the name or IP address of a DNS name server for the second parameter. Or, omit both parameters and nslookup uses the default DNS name server. Following are some tips about working in interactive mode:

    • To interrupt interactive commands at any time, press CTRL+B.

    • To exit, type exit.

    • To treat a built-in command as a computer name, precede it with the escape character (\).

    • An unrecognized command is interpreted as a computer name.

  • If the lookup request fails, nslookup prints an error message. The following table lists possible error messages.

    Error message

    Description

    Timed out

    The server did not respond to a request after a certain amount of time and a certain number of retries. You can set the time-out period with the set timeout subcommand. You can set the number of retries with the set retry subcommand.

    No response from server

    No DNS name server is running on the server computer.

    No records

    The DNS name server does not have resource records of the current query type for the computer, although the computer name is valid. The query type is specified with the set querytype command.

    Nonexistent domain

    The computer or DNS domain name does not exist.

    Connection refused

    -or-

    Network is unreachable

    The connection to the DNS name server or finger server could not be made. This error commonly occurs with ls and finger requests.

    Server failure

    The DNS name server found an internal inconsistency in its database and could not return a valid answer.

    Refused

    The DNS name server refused to service the request.

    Format error

    The DNS name server found that the request packet was not in the proper format. It may indicate an error in nslookup.

  • For more information about the nslookup command and DNS, see the following resources:

    • Microsoft Windows Resource Kits Web site

    • Lee, T., Davies, J. 2000. Microsoft Windows 2000 TCP/IP Protocols and Services Technical Reference. Redmond, Washington: Microsoft Press.

    • Albitz, P., Loukides, M. and C. Liu. 1998. DNS and BIND, Third Edition. Sebastopol, California: O'Reilly and Associates, Inc.

Examples

Each command-line option consists of a hyphen (-) followed immediately by the command name and, in some cases, an equal sign (=) and then a value. For example, to change the default query type to host (computer) information and the initial time-out to 10 seconds, type:

nslookup -querytype=hinfo -timeout=10

Formatting legend

Format

Meaning

Italic

Information that the user must supply

Bold

Elements that the user must type exactly as shown

Ellipsis (...)

Parameter that can be repeated several times in a command line

Between brackets ([])

Optional items

Between braces ({}); choices separated by pipe (|). Example: {even|odd}

Set of choices from which the user must choose only one

Courier font

Code or program output

Command-line reference A-Z

Nslookup subcommands

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