Please Whitelist This Site?
I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)
If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.
If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$document". Then just click OK.
Thanks for your understanding!
Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide
|
NOTE: Using software to mass-download the site degrades the server and is prohibited. If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.
|
|
|
|
TCP/IP DNS Name Resolution and Information Lookup Utilities (nslookup, host and dig)
(Page 3 of 5)
Interactive Use of nslookup
The interactive mode of nslookup
is selected by simply issuing the name of the command with no parameters.
This will cause the program to display the current default name servers
DNS name and address, and then provide a prompt at which the administrator
may enter commands. Interactive mode allows someone to perform multiple
lookups easily without having to type nslookup each time.
More importantly, it provides more convenient control over the types
of information that can be requested and how the lookups are performed.
The exact command set available in
an nslookup implementation can usually be determined by issuing
the command help or ? at the nslookup
prompt. Table 291
shows some of the commands that are usually found in most nslookup
implementations.
Table 291: Typical nslookup Utility Commands
Command
and Parameters
|
Description
|
<host> [<server>]
|
Look up the specified host, optionally
using the specified DNS name server. Note that there is no actual command
here, you just enter the name directly at the command prompt.
|
server
<server>
|
Change the
default server to <server>, using information obtained from the
current default server.
|
lserver <server>
|
Change the default server to
<server>, using information obtained from the initial name serverthat
is, the systems default server that was in place when the nslookup
command was started (prior to any preceding changes of the current name
server in this session).
|
root
|
Changes the
default name server to one of the DNS root
name servers.
|
ls [-t <type>] <name>
|
Requests a list of information
available for the specified domain name, by conducting a zone
transfer. By default, the host names and
addresses associated with the domain are listed; the -t
option may be used to restrict the output to a particular record type.
Other options may also be defined.
Most servers restrict the use of zone transfers to designated slave
servers, so this command may not work for ordinary clients.
|
help
|
Displays help
information (usually a list of valid commands and options).
|
?
|
Same as help (only
on some systems).
|
set all
|
Displays the
current value of all nslookup options
|
set <option>[=<value>]
|
Sets an option to control the
behavior of the utility. Most implementations include quite a number
of options, some of which are controlled by just specifying a keyword,
while others require a value for the option. For example, set
recurse tells the program to use recursive
resolution, while set norecurse
turns it off; set retry=3 sets the number of retries to
3.
|
exit
|
Quits the program.
|
Problems With nslookup
The nslookup utility is widely
deployed on both UNIX and Windows systems, but the program is not without
its critics. The complaints about it mainly center around its use of
non-standard methods of obtaining information, rather than standard
resolution routines. I have also read reports that it can produce spurious
results in some cases. One example of a significant problem with the
command is that it will abort if it is unable to perform reverse lookup
of its own IP address. This can cause confusion, because users mistake
that error for an error trying to find the name they were looking up.
For this and other reasons, a number
of people in UNIX circles consider nslookup to be a hack
of sorts, and for this reason, in some newer UNIXes nslookup has been
deprecated. This simply means that it is still included in the
operating system for compatibility, but it is not recommended and may
be removed in the future. Instead, a pair of newer utilities are provided:
host and dig.
If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support! |
|
|
Home -
Table Of Contents - Contact Us
The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005
© Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.
|