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dba3c818ae00b10388d31703e86a28415db398acTinderbox User - Copyright (C) 2004-2013 Internet Systems Consortium, Inc. ("ISC")
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - Copyright (C) 2000-2003 Internet Software Consortium.
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689023771c563d8660e45d439a207e06e96de28fMark Andrews - purpose with or without fee is hereby granted, provided that the above
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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
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e21a2904f02a03fa06b6db04d348f65fe9c67b2bMark Andrews<title>Chapter�5.�The BIND 9 Lightweight Resolver</title>
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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<link rel="prev" href="Bv9ARM.ch04.html" title="Chapter�4.�Advanced DNS Features">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<link rel="next" href="Bv9ARM.ch06.html" title="Chapter�6.�BIND 9 Configuration Reference">
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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<tr><th colspan="3" align="center">Chapter�5.�The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</th></tr>
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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<div class="titlepage"><div><div><h2 class="title">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<a name="Bv9ARM.ch05"></a>Chapter�5.�The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</h2></div></div></div>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dt><span class="sect1"><a href="Bv9ARM.ch05.html#id2573058">The Lightweight Resolver Library</a></span></dt>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dt><span class="sect1"><a href="Bv9ARM.ch05.html#lwresd">Running a Resolver Daemon</a></span></dt>
dba3c818ae00b10388d31703e86a28415db398acTinderbox User<div class="titlepage"><div><div><h2 class="title" style="clear: both">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<a name="id2573058"></a>The Lightweight Resolver Library</h2></div></div></div>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Traditionally applications have been linked with a stub resolver
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein library that sends recursive DNS queries to a local caching name
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein IPv6 once introduced new complexity into the resolution process,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein such as following A6 chains and DNAME records, and simultaneous
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein lookup of IPv4 and IPv6 addresses. Though most of the complexity was
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein then removed, these are hard or impossible
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein to implement in a traditional stub resolver.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <acronym class="acronym">BIND</acronym> 9 therefore can also provide resolution
dba3c818ae00b10388d31703e86a28415db398acTinderbox User services to local clients
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein using a combination of a lightweight resolver library and a resolver
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein daemon process running on the local host. These communicate using
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein a simple UDP-based protocol, the "lightweight resolver protocol"
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein that is distinct from and simpler than the full DNS protocol.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<div class="titlepage"><div><div><h2 class="title" style="clear: both">
dba3c818ae00b10388d31703e86a28415db398acTinderbox User<a name="lwresd"></a>Running a Resolver Daemon</h2></div></div></div>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein To use the lightweight resolver interface, the system must
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein run the resolver daemon <span><strong class="command">lwresd</strong></span> or a
00124ad0406365d39f4b2d1011ef6a76706e9df0Mark Andrews name server configured with a <span><strong class="command">lwres</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein By default, applications using the lightweight resolver library will
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein address can be overridden by <span><strong class="command">lwserver</strong></span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The daemon currently only looks in the DNS, but in the future
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein it may use other sources such as <code class="filename">/etc/hosts</code>,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The <span><strong class="command">lwresd</strong></span> daemon is essentially a
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein caching-only name server that responds to requests using the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein resolver protocol rather than the DNS protocol. Because it needs
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein to run on each host, it is designed to require no or minimal
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein configuration.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Unless configured otherwise, it uses the name servers listed on
dba3c818ae00b10388d31703e86a28415db398acTinderbox User <span><strong class="command">nameserver</strong></span> lines in <code class="filename">/etc/resolv.conf</code>
d060d8669f5558690e7faf4a1c12fe5c02a7c60dAutomatic Updater as forwarders, but is also capable of doing the resolution
d060d8669f5558690e7faf4a1c12fe5c02a7c60dAutomatic Updater autonomously if
d060d8669f5558690e7faf4a1c12fe5c02a7c60dAutomatic Updater none are specified.
d060d8669f5558690e7faf4a1c12fe5c02a7c60dAutomatic Updater The <span><strong class="command">lwresd</strong></span> daemon may also be
d060d8669f5558690e7faf4a1c12fe5c02a7c60dAutomatic Updater configured with a
dba3c818ae00b10388d31703e86a28415db398acTinderbox User <code class="filename">named.conf</code> style configuration file,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="filename">/etc/lwresd.conf</code> by default. A name
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein server may also
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein be configured to act as a lightweight resolver daemon using the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span><strong class="command">lwres</strong></span> statement in <code class="filename">named.conf</code>.
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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<td width="40%" align="left" valign="top">Chapter�4.�Advanced DNS Features�</td>
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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<td width="40%" align="right" valign="top">�Chapter�6.�<acronym class="acronym">BIND</acronym> 9 Configuration Reference</td>