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TCP/IP DNS Name Resolution and Information Lookup Utilities (nslookup, host and dig)
(Page 5 of 5)
The dig Utility
The second alternate to nslookup
is dig, which stands for Domain Information Groper
(likely a play on the supposed origin of the name ping).
It differs from the host command in that it provides considerably
more information about a domain, even when invoked in the simplest of
ways. It is also quite a bit more complicated, with a large number of
options, and features such as a batch mode for obtaining information
about many domains.
The basic syntax for the dig
command is different from nslookup or host, because if
a non-default name server is specified, it is prepended with an at sign
(@) and comes before the host to be looked up. A specific
type of resource record can also be specified, like this:
dig [@<server>] <host>
[<type>]
Table 294
shows the output from running dig on the same domain (www.pcguide.com)
that I used as an example for nslookup and host. You can
see that it provides much more information about the domain.
Table 294: DNS Name Resolution Using the dig Utility
%dig www.pcguide.com
; <<>> DiG 9.2.1 <<>> www.pcguide.com
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 15912
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 2, ADDITIONAL: 0
;; QUESTION SECTION:
;www.pcguide.com. IN A
;; ANSWER SECTION:
www.pcguide.com. 3600 IN CNAME pcguide.com.
pcguide.com. 3600 IN A 209.68.14.80
;; AUTHORITY SECTION:
pcguide.com. 3600 IN NS ns0.ns0.com.
pcguide.com. 3600 IN NS ns23.pair.com.
;; Query time: 1840 msec
;; SERVER: 209.68.1.87#53(209.68.1.87)
;; WHEN: Tue Nov 18 16:05:08 2003
;; MSG SIZE rcvd: 109Server: ns1-mar.starband.com
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The dig command
also allows specific types of resource records to be looked up, and
includes dozens of options and settings. Since this topic is already
getting very long and dig is by far the most advanced of the
three utilities, I will stop here; consult your systems documentation
for the full instructions on how dig works and a list of its
parameters.
Key Concept: Most TCP/IP implementations provide one or more utilities that can be employed by an administrator to manually resolve DNS domain names to IP addresses or perform related searches for DNS information. One of the most common is nslookup, which allows a host name to be translated to an address or vice-versa; it has both interactive and non-interactive modes. On some operating systems, nslookup has been replaced by the host utility for simple DNS lookups, and the dig program for more detailed inspections of DNS resource information. |
On The Web: The dig utility is very useful, but has still not been implemented on some systems. Fortunately, there is an online dig utility you can access using your browser on the Internet. Find it at http://www.gont.com.ar/tools/dig. |
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Version 3.0 - Version Date: September 20, 2005
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