2005-12-29 04:22:58 +00:00
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<!-- $Id: Bv9ARM.ch05.html,v 1.24.2.5.2.12 2005/10/13 02:34:00 marka Exp $ -->
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>Chapter<EFBFBD>5.<2E>The BIND 9 Lightweight Resolver</title>
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<link rel="start" href="Bv9ARM.html" title="BIND 9 Administrator Reference Manual">
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<link rel="up" href="Bv9ARM.html" title="BIND 9 Administrator Reference Manual">
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<link rel="prev" href="Bv9ARM.ch04.html" title="Chapter<65>4.<2E>Advanced DNS Features">
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<link rel="next" href="Bv9ARM.ch06.html" title="Chapter<65>6.<2E>BIND 9 Configuration Reference">
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<table width="100%" summary="Navigation header">
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<tr><th colspan="3" align="center">Chapter<EFBFBD>5.<2E>The <span class="acronym">BIND</span> 9 Lightweight Resolver</th></tr>
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<tr>
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<a accesskey="p" href="Bv9ARM.ch04.html">Prev</a><EFBFBD></td>
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<th width="60%" align="center"><EFBFBD></th>
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<td width="20%" align="right"><EFBFBD><a accesskey="n" href="Bv9ARM.ch06.html">Next</a>
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</div>
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<div class="chapter" lang="en">
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<div class="titlepage"><div><div><h2 class="title">
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<a name="Bv9ARM.ch05"></a>Chapter<EFBFBD>5.<2E>The <span class="acronym">BIND</span> 9 Lightweight Resolver</h2></div></div></div>
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<div class="toc">
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<p><b>Table of Contents</b></p>
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<dl>
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<dt><span class="sect1"><a href="Bv9ARM.ch05.html#id2550652">The Lightweight Resolver Library</a></span></dt>
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<dt><span class="sect1"><a href="Bv9ARM.ch05.html#lwresd">Running a Resolver Daemon</a></span></dt>
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</dl>
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</div>
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<div class="sect1" lang="en">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="id2550652"></a>The Lightweight Resolver Library</h2></div></div></div>
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<p>Traditionally applications have been linked with a stub resolver
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library that sends recursive DNS queries to a local caching name
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server.</p>
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<p>IPv6 once introduced new complexity into the resolution process,
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such as following A6 chains and DNAME records, and simultaneous
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lookup of IPv4 and IPv6 addresses. Though most of the complexity was
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then removed, these are hard or impossible
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to implement in a traditional stub resolver.</p>
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<p>Instead, <span class="acronym">BIND</span> 9 provides resolution services to local clients
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using a combination of a lightweight resolver library and a resolver
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daemon process running on the local host. These communicate using
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a simple UDP-based protocol, the "lightweight resolver protocol"
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that is distinct from and simpler than the full DNS protocol.</p>
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</div>
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<div class="sect1" lang="en">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="lwresd"></a>Running a Resolver Daemon</h2></div></div></div>
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<p>To use the lightweight resolver interface, the system must
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run the resolver daemon <span><strong class="command">lwresd</strong></span> or a local
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name server configured with a <span><strong class="command">lwres</strong></span> statement.</p>
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<p>By default, applications using the lightweight resolver library will make
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UDP requests to the IPv4 loopback address (127.0.0.1) on port 921. The
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address can be overridden by <span><strong class="command">lwserver</strong></span> lines in
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<code class="filename">/etc/resolv.conf</code>.</p>
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<p>The daemon currently only looks in the DNS, but in the future
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it may use other sources such as <code class="filename">/etc/hosts</code>,
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NIS, etc.</p>
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<p>The <span><strong class="command">lwresd</strong></span> daemon is essentially a
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caching-only name server that responds to requests using the lightweight
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resolver protocol rather than the DNS protocol. Because it needs
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to run on each host, it is designed to require no or minimal configuration.
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Unless configured otherwise, it uses the name servers listed on
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<span><strong class="command">nameserver</strong></span> lines in <code class="filename">/etc/resolv.conf</code>
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as forwarders, but is also capable of doing the resolution autonomously if
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none are specified.</p>
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<p>The <span><strong class="command">lwresd</strong></span> daemon may also be configured with a
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<code class="filename">named.conf</code> style configuration file, in
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<code class="filename">/etc/lwresd.conf</code> by default. A name server may also
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be configured to act as a lightweight resolver daemon using the
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<span><strong class="command">lwres</strong></span> statement in <code class="filename">named.conf</code>.</p>
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</div>
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<a accesskey="p" href="Bv9ARM.ch04.html">Prev</a><EFBFBD></td>
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<td width="20%" align="center"><EFBFBD></td>
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<td width="40%" align="right"><EFBFBD><a accesskey="n" href="Bv9ARM.ch06.html">Next</a>
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</td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">Chapter<EFBFBD>4.<2E>Advanced DNS Features<65></td>
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<td width="20%" align="center"><a accesskey="h" href="Bv9ARM.html">Home</a></td>
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<td width="40%" align="right" valign="top"><EFBFBD>Chapter<EFBFBD>6.<2E><span class="acronym">BIND</span> 9 Configuration Reference</td>
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</tr>
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