nslookup - query Internet name servers interactively


nslookup [-option ...] [host-to-find|-[server]]


The nslookup(1) is a program that is used to query Internet domain name servers. The nslookup(1) utility has two modes: interactive and non-interactive. Interactive mode allows the user to query name servers for information about various hosts and domains, or to print a list of hosts in a domain. Non-interactive mode is used to print just the name and requested information for a host or domain.


Interactive mode is entered in the following cases:

  1. When no arguments are given (the default name server will be used).
  2. When the first argument is a hyphen (-) and the second argument is the host name or Internet address of a name server.

Non-interactive mode is used when the name or Internet address of the host to be looked up is given as the first argument. The optional second argument specifies the host name or address of a name server.

The options listed under the set command (described later in this topic) can be specified in the .nslookuprc file in the user's home directory if they are listed one per line. Options can also be specified on the command line if they precede the arguments and are prefixed with a hyphen. For example, to change the default query type to host information, and the initial time-out to 10 seconds, type:

nslookup -query=hinfo  -timeout=10


Commands can be interrupted at any time by typing CTRL+C. To exit, type CTRL+D (EOF), or type exit. The command-line length must be less than 256 characters. To treat a built-in command as a host name, precede it with an escape character (\). An unrecognized command will be interpreted as a host name.

host [server]
Look up information for host using the current default server or using server, if specified. If host is an Internet address and the query type is A or PTR, the name of the host is returned. If host is a name and does not have a trailing period, the default domain name is appended to the name. (This behavior depends on the state of the set options domain, srchlist, defname, and search.)

To look up a host that is not in the current domain, append a period to the name.

server domain
lserver domain
Change the default server to domain. The lserver command uses the initial server to look up information about domain, and server uses the current default server. If an authoritative answer cannot be found, the names of servers that might have the answer are returned.
Changes the default server to the server for the root of the domain name space. Currently, the host is used. (This command is a synonym for lserver ns.internic.net.) The name of the root server can be changed with the set root command.
finger [name] [>filename]
finger [name] [>> filename]
Connects with the finger server on the current host. The current host is defined when a previous lookup for a host was successful and returned address information (see the set querytype=A command). The name is optional. You can use > and >> to redirect output in the usual manner.
ls [option] [domain] [> filename]
ls [option] [domain] [>> filename]
List the information available for domain, optionally creating or appending to filename. The default output contains host names and their Internet addresses. When output is directed to a file, hash marks (#) are printed for every 50 records received from the server. Option can be one of the following:
Lists all records of the specified type (see querytype below).
Lists aliases of hosts in the domain; synonym for -t CNAME.
Lists all records for the domain; synonym for -t ANY.
Lists CPU and operating system information for the domain; synonym for -t HINFO.
Lists well-known services of hosts in the domain; synonym for -t WKS.
view filename
Sorts and lists the output of one or more previous ls(1) commands with more(1).
Prints a brief summary of commands.
Exits the program.
This command is used to change state information that affects the lookups. Valid keywords are:
Prints the current values of the frequently used options to set. Information about the current default server and host is also printed.
Change the query class to one of the following:
The Internet class
The Chaos class
The MIT Athena Hesiod class
Wildcard (any of the above)

The class specifies the protocol group of the information.

(Default = IN; abbreviation = cl)

Turn debugging mode on. Considerably more information is printed about the packet sent to the server and the resulting answer.

(Default = nodebug; abbreviation = [no]deb)

Turn exhaustive debugging mode on. All fields of every packet are printed.

(Default = nod2)

Change the default domain name to name. 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 domain if it has at least two components in its name. For example, if the default domain is topaz.anycollege.edu, the search list is topaz.anycollege.edu and anycollege.edu. Use the set srchlist command to specify a different list. Use the set all command to display the list.

(Default = value from hostname(1), /etc/resolv.conf, or LOCALDOMAIN; abbreviation = do)

Change the default domain name to name1 and the domain search list to name1, name2, and so on. A maximum of six names separated by slashes (/) can be specified. For example,
set srchlist=/helios.anycollege.edu/anycollege.edu

sets the domain to topaz.anycollege.edu and the search list to the three names. This command overrides the default domain name and search list of the set domain command. Use the set all command to display the list.

(Default = value based on hostname(1), /etc/resolv.conf, or LOCALDOMAIN; abbreviation = srchl)

If set, append the default domain name to a single-component lookup request (that is, one that does not contain a period).

(Default = defname; abbreviation = [no]defname)

If the lookup request contains at least one period but does not end with a trailing period, append the domain names in the domain search list to the request until an answer is received.

(Default = search; abbreviation = [no]sea)

Change the default Transmission Control Protocol/User Datagram Protocol (TCP/UDP) name server port to value.

(Default = 53; abbreviation = po)

Change the type of information query to one of the following:
the host's Internet address.
The canonical name for an alias.
The host CPU and operating system type.
The mailbox or mail list information.
The mail exchanger.
The name server for the named zone.
The host name if the query is an Internet address; otherwise, the pointer to other information.
The domain's start-of-authority information.
The text information.
The user information.
The supported well-known services.

Other types (ANY, AXFR, MB, MD, MF, NULL) are described in the RFC-1035 document.

(Default = A; abbreviations = q, ty)

Tell the name server to query other servers if it does not have the information.

(Default = recurse; abbreviation = [no]rec)

Set the number of retries to number. When a reply to a request is not received within a certain amount of time (changed with set timeout, the time-out period is doubled and the request is resent. The retry value controls how many times a request is re-sent before it stops re-sending it.

(Default = 4, abbreviation = ret)

Change the name of the root server to host. This affects the root command.

(Default = ns.internic.net.; abbreviation = ro)

Change the initial time-out interval for waiting for a reply to number seconds. Each retry doubles the time-out period.

(Default = 5 seconds; abbreviation =ti)

Always use a virtual circuit when sending requests to the server.

(Default = novc; abbreviation = [no]v)

Ignore packet truncation errors.

(Default = noignoretc; abbreviation = [no]ig)


If the lookup request was not successful, an error message is printed. Possible errors are:

Timed out
The server did not respond to a request after a certain amount of time (changed with set timeout=value and a certain number of retries (changed with set retry=value).
No response from server
No name server is running on the server computer.
No records
The server does not have resource records of the current query type for the host, although the host name is valid. The query type is specified with the set querytype command.
Nonexistent domain
The host or domain name does not exist.
Connection refused
Network is unreachable
The connection to the name or finger server could not be made at the current time. This error commonly occurs with ls(1) and finger(1) requests.
Server failure
The name server found an internal inconsistency in its database and could not return a valid answer.
The name server refused to service the request.
Format error
The name server found that the request packet was not in the proper format. It might indicate an error in nslookup(1).


Initial domain name and name server addresses
User's initial options
Summary of commands


File containing host aliases
Overrides default domain




RFC-1034, Domain Names - Concepts and Facilities; RFC-1035, Domain Names - Implementation and Specification.