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+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
+ "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+<meta name="generator" content="HTML Tidy, see www.w3.org" />
+<title>DNS Tools</title>
+<meta name="GENERATOR" content="Modular DocBook HTML Stylesheet Version 1.7" />
+<link rel="HOME" title="Slackware Linux Essentials" href="index.html" />
+<link rel="UP" title="Basic Network Commands" href="basic-network-commands.html" />
+<link rel="PREVIOUS" title="traceroute" href="basic-network-commands-traceroute.html" />
+<link rel="NEXT" title="finger" href="basic-network-commands-finger.html" />
+<link rel="STYLESHEET" type="text/css" href="docbook.css" />
+<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
+</head>
+<body class="SECT1" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#840084"
+alink="#0000FF">
+<div class="NAVHEADER">
+<table summary="Header navigation table" width="100%" border="0" cellpadding="0"
+cellspacing="0">
+<tr>
+<th colspan="3" align="center">Slackware Linux Essentials</th>
+</tr>
+
+<tr>
+<td width="10%" align="left" valign="bottom"><a
+href="basic-network-commands-traceroute.html" accesskey="P">Prev</a></td>
+<td width="80%" align="center" valign="bottom">Chapter 13 Basic Network Commands</td>
+<td width="10%" align="right" valign="bottom"><a
+href="basic-network-commands-finger.html" accesskey="N">Next</a></td>
+</tr>
+</table>
+
+<hr align="LEFT" width="100%" />
+</div>
+
+<div class="SECT1">
+<h1 class="SECT1"><a id="BASIC-NETWORK-COMMANDS-DNS"
+name="BASIC-NETWORK-COMMANDS-DNS">13.3 DNS Tools</a></h1>
+
+<p>Domain Name Service (DNS for short) is that magical protocol that allows your computer
+to turn meaningless domain names like www.slackware.com into meaningful IP address like
+<tt class="HOSTID">64.57.102.34</tt>. Computers can't route packets to www.slackware.com,
+but they can route packets to that domain name's IP address. This gives us a convenient
+way to remember machines. Without DNS we'd have to keep a mental database of just what IP
+address belongs to what computer, and that's assuming the IP address doesn't change.
+Clearly using names for computers is better, but how do we map names to IP addresses?</p>
+
+<div class="SECT2">
+<h2 class="SECT2"><a id="AEN4475" name="AEN4475">13.3.1 <tt
+class="COMMAND">host</tt></a></h2>
+
+<p><tt class="COMMAND">host</tt>(1) can do this for us. <tt class="COMMAND">host</tt> is
+used to map names to IP addresses. It is a very quick and simple utility without a lot of
+functions.</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="SCREEN">
+<samp class="PROMPT">%</samp> <kbd class="USERINPUT">host www.slackware.com</kbd>
+www.slackware.com is an alias for slackware.com.
+slackware.com has address 64.57.102.34
+</pre>
+</td>
+</tr>
+</table>
+
+<p>But let's say for some reason we want to map an IP address to a domain name; what
+then?</p>
+</div>
+
+<div class="SECT2">
+<h2 class="SECT2"><a id="AEN4487" name="AEN4487">13.3.2 <tt
+class="COMMAND">nslookup</tt></a></h2>
+
+<p><tt class="COMMAND">nslookup</tt> is a tried and true program that has weathered the
+ages. <tt class="COMMAND">nslookup</tt> has been deprecated and may be removed from
+future releases. There is not even a man page for this program.</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="SCREEN">
+<samp class="PROMPT">%</samp> <kbd class="USERINPUT">nslookup 64.57.102.34</kbd>
+Note: nslookup is deprecated and may be removed from future releases.
+Consider using the `dig' or `host' programs instead. Run nslookup with
+the `-sil[ent]' option to prevent this message from appearing.
+Server: 192.168.1.254
+Address: 192.168.1.254#53
+
+Non-authoritative answer:
+www.slackware.com canonical name = slackware.com.
+Name: slackware.com
+Address: 64.57.102.34
+</pre>
+</td>
+</tr>
+</table>
+</div>
+
+<div class="SECT2">
+<h2 class="SECT2"><a id="AEN4496" name="AEN4496">13.3.3 <tt
+class="COMMAND">dig</tt></a></h2>
+
+<p>The meanest dog in the pound, the domain information groper, <tt
+class="COMMAND">dig</tt>(1) for short, is the go-to program for finding DNS information.
+<tt class="COMMAND">dig</tt> can grab just about anything from a DNS server including
+reverse lookups, A, CNAME, MX, SP, and TXT records. <tt class="COMMAND">dig</tt> has many
+command line options and if you're not familiar with it you should read through it's
+extensive man page.</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="SCREEN">
+<samp class="PROMPT">%</samp> <kbd
+class="USERINPUT">dig @192.168.1.254 www.slackware.com mx</kbd>
+
+; &lt;&lt;&#62;&#62; DiG 9.2.2 &lt;&lt;&#62;&#62; @192.168.1.254 www.slackware.com mx
+;; global options: printcmd
+;; Got answer:
+;; -&#62;&#62;HEADER&lt;&lt;- opcode: QUERY, status: NOERROR, id: 26362
+;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 2, ADDITIONAL: 2
+
+;; QUESTION SECTION:
+;www.slackware.com. IN MX
+
+;; ANSWER SECTION:
+www.slackware.com. 76634 IN CNAME slackware.com.
+slackware.com. 86400 IN MX 1 mail.slackware.com.
+
+;; AUTHORITY SECTION:
+slackware.com. 86400 IN NS ns1.cwo.com.
+slackware.com. 86400 IN NS ns2.cwo.com.
+
+;; ADDITIONAL SECTION:
+ns1.cwo.com. 163033 IN A 64.57.100.2
+ns2.cwo.com. 163033 IN A 64.57.100.3
+
+;; Query time: 149 msec
+;; SERVER: 192.168.1.254#53(192.168.1.254)
+;; WHEN: Sat Nov 6 16:59:31 2004
+;; MSG SIZE rcvd: 159
+</pre>
+</td>
+</tr>
+</table>
+
+<p>This should give you an idea how <tt class="COMMAND">dig</tt> works.
+&#8220;@192.168.1.254&#8221; specifies the dns server to use.
+&#8220;www.slackware.com&#8221; is the domain name I am performing a lookup on, and
+&#8220;mx&#8221; is the type of lookup I am performing. The above query tells me that
+e-mail to <tt class="HOSTID">www.slackware.com</tt> will instead be sent to <tt
+class="HOSTID">mail.slackware.com</tt> for delivery.</p>
+</div>
+</div>
+
+<div class="NAVFOOTER">
+<hr align="LEFT" width="100%" />
+<table summary="Footer navigation table" width="100%" border="0" cellpadding="0"
+cellspacing="0">
+<tr>
+<td width="33%" align="left" valign="top"><a
+href="basic-network-commands-traceroute.html" accesskey="P">Prev</a></td>
+<td width="34%" align="center" valign="top"><a href="index.html"
+accesskey="H">Home</a></td>
+<td width="33%" align="right" valign="top"><a href="basic-network-commands-finger.html"
+accesskey="N">Next</a></td>
+</tr>
+
+<tr>
+<td width="33%" align="left" valign="top"><tt class="COMMAND">traceroute</tt></td>
+<td width="34%" align="center" valign="top"><a href="basic-network-commands.html"
+accesskey="U">Up</a></td>
+<td width="33%" align="right" valign="top"><tt class="COMMAND">finger</tt></td>
+</tr>
+</table>
+</div>
+</body>
+</html>
+