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5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder<title>Chapter�5.�The BIND 9 Lightweight Resolver</title>
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c55a0f77be7e88d3620b419ec8961f4379a586e3Klaus Luettich<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
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857992065be4ed40a72c6296b6c0aec62ab4c5b9Christian Maeder<tr><th colspan="3" align="center">Chapter�5.�The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</th></tr>
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder<a accesskey="p" href="Bv9ARM.ch04.html">Prev</a>�</td>
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5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder<div class="titlepage"><div><div><h2 class="title">
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder<a name="Bv9ARM.ch05"></a>Chapter�5.�The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</h2></div></div></div>
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder<dt><span class="sect1"><a href="Bv9ARM.ch05.html#id2571844">The Lightweight Resolver Library</a></span></dt>
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder<dt><span class="sect1"><a href="Bv9ARM.ch05.html#lwresd">Running a Resolver Daemon</a></span></dt>
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder<div class="titlepage"><div><div><h2 class="title" style="clear: both">
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder<a name="id2571844"></a>The Lightweight Resolver Library</h2></div></div></div>
ac0bbbcb2774629bb87986e69cf53d3402c5f575Christian Maeder Traditionally applications have been linked with a stub resolver
ac0bbbcb2774629bb87986e69cf53d3402c5f575Christian Maeder library that sends recursive DNS queries to a local caching name
ebe517300051f765f2ed856a789dd5613d681ab0Klaus Luettich IPv6 once introduced new complexity into the resolution process,
8b0f493ae42bad8b94918cc0957f1af57096cda4Felix Reckers such as following A6 chains and DNAME records, and simultaneous
c55a0f77be7e88d3620b419ec8961f4379a586e3Klaus Luettich lookup of IPv4 and IPv6 addresses. Though most of the complexity was
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder then removed, these are hard or impossible
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder to implement in a traditional stub resolver.
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder <acronym class="acronym">BIND</acronym> 9 therefore can also provide resolution
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder services to local clients
ebe517300051f765f2ed856a789dd5613d681ab0Klaus Luettich using a combination of a lightweight resolver library and a resolver
8b0f493ae42bad8b94918cc0957f1af57096cda4Felix Reckers daemon process running on the local host. These communicate using
8b0f493ae42bad8b94918cc0957f1af57096cda4Felix Reckers a simple UDP-based protocol, the "lightweight resolver protocol"
c55a0f77be7e88d3620b419ec8961f4379a586e3Klaus Luettich that is distinct from and simpler than the full DNS protocol.
ac0bbbcb2774629bb87986e69cf53d3402c5f575Christian Maeder<div class="titlepage"><div><div><h2 class="title" style="clear: both">
ce50fe187cdae64e75e510daafb78156280bdb91Christian Maeder<a name="lwresd"></a>Running a Resolver Daemon</h2></div></div></div>
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder To use the lightweight resolver interface, the system must
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder run the resolver daemon <span><strong class="command">lwresd</strong></span> or a
8b0f493ae42bad8b94918cc0957f1af57096cda4Felix Reckers name server configured with a <span><strong class="command">lwres</strong></span>
5d4038657f6a63e131f5804af2f7957b69e15a43Klaus Luettich By default, applications using the lightweight resolver library will
c432483b64662e8db604a58758cd18ea7fa65659Christian Maeder UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
857992065be4ed40a72c6296b6c0aec62ab4c5b9Christian Maeder address can be overridden by <span><strong class="command">lwserver</strong></span>
e8d782e6e650b71a2b0ee8461fd8d9fa31525591Christian Maeder <code class="filename">/etc/resolv.conf</code>.
96ef2e46d048c357927f2795a40e9e66f21b85fbSonja Gröning The daemon currently only looks in the DNS, but in the future
8659594bb40eb5f3da5439692f0908300947191eSonja Gröning it may use other sources such as <code class="filename">/etc/hosts</code>,
96ef2e46d048c357927f2795a40e9e66f21b85fbSonja Gröning The <span><strong class="command">lwresd</strong></span> daemon is essentially a
96ef2e46d048c357927f2795a40e9e66f21b85fbSonja Gröning caching-only name server that responds to requests using the
7d09621f989f5e6dfbf603b36b2fccbacf639a3cTill Mossakowski resolver protocol rather than the DNS protocol. Because it needs
8b0f493ae42bad8b94918cc0957f1af57096cda4Felix Reckers to run on each host, it is designed to require no or minimal
857992065be4ed40a72c6296b6c0aec62ab4c5b9Christian Maeder configuration.
8b0f493ae42bad8b94918cc0957f1af57096cda4Felix Reckers Unless configured otherwise, it uses the name servers listed on
857992065be4ed40a72c6296b6c0aec62ab4c5b9Christian Maeder <span><strong class="command">nameserver</strong></span> lines in <code class="filename">/etc/resolv.conf</code>
857992065be4ed40a72c6296b6c0aec62ab4c5b9Christian Maeder as forwarders, but is also capable of doing the resolution
857992065be4ed40a72c6296b6c0aec62ab4c5b9Christian Maeder autonomously if
7d09621f989f5e6dfbf603b36b2fccbacf639a3cTill Mossakowski none are specified.
8b0f493ae42bad8b94918cc0957f1af57096cda4Felix Reckers The <span><strong class="command">lwresd</strong></span> daemon may also be
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder configured with a
327a9b9bf44b6e33f71fee7526dc1c0035251591Christian Maeder <code class="filename">named.conf</code> style configuration file,
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder <code class="filename">/etc/lwresd.conf</code> by default. A name
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder server may also
0e012772df2ce0dc7e8f0fe3acf458c2871dcfbcChristian Maeder be configured to act as a lightweight resolver daemon using the
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder <span><strong class="command">lwres</strong></span> statement in <code class="filename">named.conf</code>.
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder The number of client queries that the <span><strong class="command">lwresd</strong></span>
857992065be4ed40a72c6296b6c0aec62ab4c5b9Christian Maeder daemon is able to serve can be set using the
857992065be4ed40a72c6296b6c0aec62ab4c5b9Christian Maeder <code class="option">lwres-tasks</code> and <code class="option">lwres-clients</code>
857992065be4ed40a72c6296b6c0aec62ab4c5b9Christian Maeder statements in the configuration.
88c800932dd7053322501ea2039d9f234be6866cKlaus Luettich<table width="100%" summary="Navigation footer">
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ed9207cf24e96b0d6f59985822054ae28cb69b2eChristian Maeder<td width="40%" align="left" valign="top">Chapter�4.�Advanced DNS Features�</td>
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fa21fba9ceb1ddf7b3efd54731a12ed8750191d8Christian Maeder<td width="40%" align="right" valign="top">�Chapter�6.�<acronym class="acronym">BIND</acronym> 9 Configuration Reference</td>
5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder<p style="text-align: center;">BIND 9.11.0pre-alpha</p>