nslookup command

8/3/2019 Nslookup Command

1/7

[Next Article | Previous Article | Book Contents | Library Home | Legal | Search ]

Commands Reference, Volume 4

nslookup Command

Purpose

Queries Internet domain name servers.

Syntax

nslookup [ -Option ... ] [Host] [ -ameServer]

Description

The nslookup command queries Internet domain name servers in two modes. Interactive mode allows you toquery name servers for information about various hosts and domains, or to print a list of the hosts in a

domain. In noninteractive mode, the names and requested information are printed for a specified host or

domain.

The nslookup command enters interactive mode when no arguments are given, or when the first argument is

a - (minus sign) and the second argument is the host name or Internet address of a name server. When no

arguments are given, the command queries the default name server. The - (minus sign) invokes an optional

subcommand (-Option... variable). With the exception of the set command, these subcommands are specified

on the command line and must precede the nslookup command arguments. The set subcommand options can

alternatively be specified in the .nslookuprc file in the user's home directory.

The nslookup command executes in noninteractive mode when the first argument is the name or Internet

address of the host being searched for. In this case, the host name or Internet address of the name server is

optional.

The noninteractive command looks up information for the specifiedHostusing the default name server or the

name server specified by theameServerparameter. If theHostparameter specifies an Internet address and

the query type is A orPTR, the name of the host is returned. If theHostparameter specifies a name and the

name does not have a trailing period, the default domain name is appended to the name. To look up a host not

in the current domain, append a single period to the name.

ote: If they are specified in the .nslookuprc file of the user's home directory, the setsubcommand's domain, srchlist, defname, and search options can affect the behavior of the

noninteractive command.

Subcommands

The following commands can be interrupted at any time by entering a Ctrl-C key sequence. To exit, enter a

Ctrl-D key sequence or type exit. To treat a built-in command as a host name, precede it with an escape

character, which is a \. Unrecognized commands are interpreted as host names.

The following subcommands are recognized by the nslookup command:

kup Command http://nfosolutions.com/doc_link/en_US/a_doc_lib/cmds/aixcmds4

5/22/2009


2/7

finger [ame] [>Fileame]

finger [ame] [>>Fileame]

Connects with the finger daemon server on the current host. The current

host is defined when a previous lookup for a host was successful and

returned address information, such as that returned with the set

querytype=A command. Theame parameter, which specifies a user

name, is optional. The > and >> characters can be used to redirect

output to a new or existing file.

serverDomain

lserverDomain

Changes the default server to the value specified by theDomain

parameter. The lserver subcommand uses the initial server to look up

information about the domain. The server subcommand uses the current

default server. If an authoritative answer cannot be found, the names of

any additional servers that might have the answer are returned.

root Changes the default server to the server for the root of the domain name

space. Currently, the host ns.nic.ddn.mil is used. The name of the

root server can be changed with the setroot subcommand. (The root

subcommand is synonymous with the lserver ns.nic.ddn.mil

subcommand.)

ls [Option]Domain [>Fileame]

ls [Option]Domain [>>Fileame]

Lists the information available for theDomain specified, optionally

creating or appending the output to the file specified by theFileame

parameter. The default output contains host names and their Internetaddresses. Possible values for the Option parameter are:

-tQueryType

Lists all records of the specified type. The default record type is

A. Valid types are:

A

Host's Internet address

CAME

Canonical name for an alias

HIFO

Host CPU and operating system typeKEY

Security Key Record

MIFO

Mailbox or mail list information

MX

Mail exchanger

S

Nameserver for the named zone

PTR

Host name if the query is an Internet address; otherwise, the

pointer to other informationSIG

Signature Record

SOA

Domain's "start-of-authority" information

TXT

Text information

UIFO

User information

WKS


5/22/2009


3/7

Supported well-known services

-a

Lists aliases of hosts in the domain (synonymous with the -t

CAME option).

-d

Lists all records for the domain (synonymous with the -t AY

option).

-h

Lists CPU and operating system information for the domain(synonymous with the -t HIFO option).

-s

Lists well-known services of hosts in the domain (synonymous

with the -t WKS option).

ote: When output is redirected to a file, hash marks are

printed for every 50 records received from the server.

viewFileame Sorts the output of previous ls commands and lists them using the more

command.

help

? Prints a brief summary of commands.

exit Exits the program.

setKeyword[=Value] Changes state information that affects lookups. This subcommand can be

specified on the command line or optionally included in the .nslookuprc

file in the user's home directory. Valid keywords are:

all

Prints the current values of the frequently used options to set.

Information about the current default server and host is also

printed.class=Value

Changes the query class to one of the following. The class

specifies the protocol group of the information. The default is I.

I

Internet class

CHAOS

Chaos class

HESIOD

MIT Althena Hesiod class

AY

Wildcard (any of the above)[no]debug

Turns debugging mode on. The default is nodebug (off).

[no]d2

Turns comprehensive debugging on. The default is nod2 (off).

domain=ame

Changes the default domain name to the name specified by the

ame parameter. The default domain name is appended to a

lookup request, depending on the state of the defname and search

options. The domain search list contains the parents of the default


5/22/2009


4/7

domain if the search list has at least two components in its name.

For example, if the default domain is CC.Berkeley.EDU, the

search list is CC.Berkeley.EDU and Berkeley.EDU. Use the set

srchlist command to specify a different list. Use the setall

command to display the list. The default of the domain=ame

option is the value specified in the system's hostname,

/etc/resolv.conf, orLOCALDOMAI file.

srchlst=ame1/ame2/...

Changes the default domain name to the name specified by theame1 parameter, and changes the domain search list to the

names specified by theame1,ame2,..., parameters. A

maximum of six names separated by slashes can be specified. Use

the setall command to display the list of names. The default

values are specified in the system's hostname, /etc/resolv.conf, or

LOCALDOMAI file.

ote: This command overrides the default domain

name and search list of the setdomain command

option.

[no]defname

Appends the default domain name to a single component lookup

request (one that does not include a period). The default is

defname (append).

[no]search

Appends the domain names in the domain search list to the request

until an answer is received, if the lookup request contains a period

other than a trailing period. The default is search.

port=Value

Changes the default TCP/UDP nameserver port to the number

specified by the Value parameter. The default value is 53.querytype=Value

type=Value Changes the information query to one of the following values. The

default is A.

A

Host's Internet address

AY

Any of the options available.

CAME

Canonical name for an aliasHIFO

Host CPU and operating system type

KEY

Security Key Record

MIFO

Mailbox or mail list information

MX

Mail exchanger

S


5/22/2009


5/7

Name server for the named zone

PTR

Host name if the query is an Internet address; otherwise, the

pointer to other information

SIG

Signature Record

SOA

Domain's "start-of-authority" information

TXT

Text information

UIFO

User information

WKS

Supported well-known services

[no]recurse

Tells the name server to query other servers if it does not have

information. The default is recurse.

retry=umber

Sets the number of times a request is retried to the value specified

by theumberparameter. When a reply to a request is not

received within the time frame specified by the settimeout

command, the timeout period is doubled and the request resent.

This subcommand controls the number of times a request is sent

before timing out. The default value is 4.

root=Host

Changes the name of the root server to the name specified by the

Hostparameter. The default is ns.nic.ddn.mil.

timeout=umber

Changes the initial time-out interval for waiting for a reply to the

number of seconds specified by theumberparameter. The

default value is 5 seconds.

[no]vc

Uses a virtual circuit when sending requests to the server. The

default is novc (no virtual circuit).

[no]ignoretc

Ignores packet truncation errors. The default is noignoretc (do not

ignore).

Examples

To change the default query type to host information (HINFO) and the initial time-out to 10 seconds,

enter:

nslookup -query=hinfo -timeout=10

1.

To set the domain and the search list to three names, lcs.MIT.EDU, ai.MIT.EDU, and MIT.EDU, enter:

nslookup -set srchlist=lcs.MIT.EDU/ai.MIT.EDU/MIT.EDU

This command overrides the default domain name and search list of the setdomain command. Use the

setall command to display the list.

2.


5/22/2009


6/7

To determine whether a name specifies a host, domain, or other entity, enter:

nslookup -querytype=ANY austin.ibm.com

The nslookup command returns all available information about the name austin.ibm.com, including

Statement of Authority (SOA), name server, mail exchanger, and host Internet address information, as

follows:

Server: benames.austin.ibm.com

Address: 9.3.199.2

austin.ibm.com origin = ausname1.austin.ibm.com

mail addr = brian.chriss.austin.ibm.com

serial=1993081210,refresh=3600,retry=300,expire=604800, min=86400

austin.ibm.com nameserver = ausname1.austin.ibm.com

austin.ibm.com nameserver = bb3names.austin.ibm.com

austin.ibm.com nameserver = benames.austin.ibm.com

austin.ibm.com nameserver = b45names.austin.ibm.com

austin.ibm.com nameserver = bbcnames.austin.ibm.com

austin.ibm.com nameserver = netmail.austin.ibm.com

austin.ibm.com preference = 10, mail exchanger = netmail.austin.ibm.com

austin.ibm.com inet address = 129.35.208.98

ausname1.austin.ibm.com inet address = 129.35.17.2

bb3names.austin.ibm.com inet address = 129.35.208.99benames.austin.ibm.com inet address = 9.3.199.2

b45names.austin.ibm.com inet address = 129.35.49.2

bbcnames.austin.ibm.com inet address = 129.35.17.68

netmail.austin.ibm.com inet address = 129.35.208.98

3.

To perform a noninteractive query on host opus, enter:

nslookup opus

The nslookup command responds similarly to the host command. The command returns the domain

name and Internet address of host opus, as follows:

Name: opus.austin.ibm.com

Address: 129.35.129.223

If host opus had been a name server (a host running the named daemon with an empty /etc/resolv.conf

file), the following information would have been displayed:

Server: loopback

Address: 0.0.0.0

4.

Exit Status

When a lookup request is not successful, the nslookup command returns one of the following error messages:

Timed Out Indicates the server did not respond to the request after the specified number of

retries.

o Response from Server Indicates that a name server is not running on the server machine.

o Records Indicates the server does not have the resource records of the specified query

type for the host, although the host name is valid.

on-Existent Domain Indicates the host or domain name does not exist.

Connection Refused Indicates the connection to the name or finger server could not be made at the

time of the inquiry. This error is typically associated with ls and finger requests.


5/22/2009


7/7

etwork Is Unreachable Indicates the connection to the name or finger server could not be made at the

time of the inquiry. This error is typically associated with ls and finger requests.

Server Failure Indicates the name server encountered an internal inconsistency and could not

return a valid answer.

Refused Indicates the name server refused to service the request.

Format Error Indicates the name server refused the request packet because it was not in the

proper format.

Files

/usr/bin/nslookup Contains the nslookup command.

/etc/resolv.conf Contains the initial domain name and nameserver addresses.

$HOME/.nslookuprc Contains the user's initial options.

HOSTALIASES Contains the host aliases.

LOCALDOMAI Contains the override default domain.

Related Information

namerslv command, traceroute command.

named daemon.

res_query subroutine, res_search subroutine.

resolv.conffile format for TCP/IP.

TCP/IP Name Resolution inAIX Version 4.3 System Management Guide: Communications and etworks.

[Next Article | Previous Article | Book Contents | Library Home | Legal | Search ]


nslookup command

Documents