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a180a41bba1d50822df23fff0099e90b86638b89vboxsync<!-- $Id: Bv9ARM.ch05.html,v 1.63 2007/05/30 02:30:14 marka Exp $ -->
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a180a41bba1d50822df23fff0099e90b86638b89vboxsync<title>Chapter�5.�The BIND 9 Lightweight Resolver</title>
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a180a41bba1d50822df23fff0099e90b86638b89vboxsync<tr><th colspan="3" align="center">Chapter�5.�The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</th></tr>
a180a41bba1d50822df23fff0099e90b86638b89vboxsync<a accesskey="p" href="Bv9ARM.ch04.html">Prev</a>�</td>
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a180a41bba1d50822df23fff0099e90b86638b89vboxsync<a name="Bv9ARM.ch05"></a>Chapter�5.�The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</h2></div></div></div>
a180a41bba1d50822df23fff0099e90b86638b89vboxsync<dt><span class="sect1"><a href="Bv9ARM.ch05.html#id2572285">The Lightweight Resolver Library</a></span></dt>
a180a41bba1d50822df23fff0099e90b86638b89vboxsync<dt><span class="sect1"><a href="Bv9ARM.ch05.html#lwresd">Running a Resolver Daemon</a></span></dt>
a180a41bba1d50822df23fff0099e90b86638b89vboxsync<div class="titlepage"><div><div><h2 class="title" style="clear: both">
a180a41bba1d50822df23fff0099e90b86638b89vboxsync<a name="id2572285"></a>The Lightweight Resolver Library</h2></div></div></div>
a180a41bba1d50822df23fff0099e90b86638b89vboxsync Traditionally applications have been linked with a stub resolver
a180a41bba1d50822df23fff0099e90b86638b89vboxsync library that sends recursive DNS queries to a local caching name
a180a41bba1d50822df23fff0099e90b86638b89vboxsync IPv6 once introduced new complexity into the resolution process,
a180a41bba1d50822df23fff0099e90b86638b89vboxsync such as following A6 chains and DNAME records, and simultaneous
a180a41bba1d50822df23fff0099e90b86638b89vboxsync lookup of IPv4 and IPv6 addresses. Though most of the complexity was
a180a41bba1d50822df23fff0099e90b86638b89vboxsync then removed, these are hard or impossible
a180a41bba1d50822df23fff0099e90b86638b89vboxsync to implement in a traditional stub resolver.
a180a41bba1d50822df23fff0099e90b86638b89vboxsync <acronym class="acronym">BIND</acronym> 9 therefore can also provide resolution
a180a41bba1d50822df23fff0099e90b86638b89vboxsync services to local clients
a180a41bba1d50822df23fff0099e90b86638b89vboxsync using a combination of a lightweight resolver library and a resolver
a180a41bba1d50822df23fff0099e90b86638b89vboxsync daemon process running on the local host. These communicate using
a180a41bba1d50822df23fff0099e90b86638b89vboxsync a simple UDP-based protocol, the "lightweight resolver protocol"
a180a41bba1d50822df23fff0099e90b86638b89vboxsync that is distinct from and simpler than the full DNS protocol.
a180a41bba1d50822df23fff0099e90b86638b89vboxsync<div class="titlepage"><div><div><h2 class="title" style="clear: both">
a180a41bba1d50822df23fff0099e90b86638b89vboxsync<a name="lwresd"></a>Running a Resolver Daemon</h2></div></div></div>
a180a41bba1d50822df23fff0099e90b86638b89vboxsync To use the lightweight resolver interface, the system must
a180a41bba1d50822df23fff0099e90b86638b89vboxsync run the resolver daemon <span><strong class="command">lwresd</strong></span> or a
a180a41bba1d50822df23fff0099e90b86638b89vboxsync name server configured with a <span><strong class="command">lwres</strong></span>
a180a41bba1d50822df23fff0099e90b86638b89vboxsync By default, applications using the lightweight resolver library will
a180a41bba1d50822df23fff0099e90b86638b89vboxsync UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
a180a41bba1d50822df23fff0099e90b86638b89vboxsync address can be overridden by <span><strong class="command">lwserver</strong></span>
a180a41bba1d50822df23fff0099e90b86638b89vboxsync The daemon currently only looks in the DNS, but in the future
a180a41bba1d50822df23fff0099e90b86638b89vboxsync it may use other sources such as <code class="filename">/etc/hosts</code>,
a180a41bba1d50822df23fff0099e90b86638b89vboxsync The <span><strong class="command">lwresd</strong></span> daemon is essentially a
a180a41bba1d50822df23fff0099e90b86638b89vboxsync caching-only name server that responds to requests using the
a180a41bba1d50822df23fff0099e90b86638b89vboxsync lightweight
a180a41bba1d50822df23fff0099e90b86638b89vboxsync resolver protocol rather than the DNS protocol. Because it needs
a180a41bba1d50822df23fff0099e90b86638b89vboxsync to run on each host, it is designed to require no or minimal
a180a41bba1d50822df23fff0099e90b86638b89vboxsync configuration.
a180a41bba1d50822df23fff0099e90b86638b89vboxsync Unless configured otherwise, it uses the name servers listed on
a180a41bba1d50822df23fff0099e90b86638b89vboxsync <span><strong class="command">nameserver</strong></span> lines in <code class="filename">/etc/resolv.conf</code>
a180a41bba1d50822df23fff0099e90b86638b89vboxsync as forwarders, but is also capable of doing the resolution
a180a41bba1d50822df23fff0099e90b86638b89vboxsync autonomously if
a180a41bba1d50822df23fff0099e90b86638b89vboxsync none are specified.
a180a41bba1d50822df23fff0099e90b86638b89vboxsync The <span><strong class="command">lwresd</strong></span> daemon may also be
a180a41bba1d50822df23fff0099e90b86638b89vboxsync configured with a
a180a41bba1d50822df23fff0099e90b86638b89vboxsync <code class="filename">named.conf</code> style configuration file,
a180a41bba1d50822df23fff0099e90b86638b89vboxsync <code class="filename">/etc/lwresd.conf</code> by default. A name
a180a41bba1d50822df23fff0099e90b86638b89vboxsync server may also
a180a41bba1d50822df23fff0099e90b86638b89vboxsync be configured to act as a lightweight resolver daemon using the
a180a41bba1d50822df23fff0099e90b86638b89vboxsync <span><strong class="command">lwres</strong></span> statement in <code class="filename">named.conf</code>.
a180a41bba1d50822df23fff0099e90b86638b89vboxsync<a accesskey="p" href="Bv9ARM.ch04.html">Prev</a>�</td>
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a180a41bba1d50822df23fff0099e90b86638b89vboxsync<td width="40%" align="left" valign="top">Chapter�4.�Advanced DNS Features�</td>
a180a41bba1d50822df23fff0099e90b86638b89vboxsync<td width="20%" align="center"><a accesskey="h" href="Bv9ARM.html">Home</a></td>
a180a41bba1d50822df23fff0099e90b86638b89vboxsync<td width="40%" align="right" valign="top">�Chapter�6.�<acronym class="acronym">BIND</acronym> 9 Configuration Reference</td>