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9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor - Copyright (C) 2004-2015 Internet Systems Consortium, Inc. ("ISC")
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9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor<title>Chapter�5.�The BIND 9 Lightweight Resolver</title>
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9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor<tr><th colspan="3" align="center">Chapter�5.�The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</th></tr>
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor<a accesskey="p" href="Bv9ARM.ch04.html">Prev</a>�</td>
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9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor<div class="chapter" title="Chapter�5.�The BIND 9 Lightweight Resolver">
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor<div class="titlepage"><div><div><h2 class="title">
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor<a name="Bv9ARM.ch05"></a>Chapter�5.�The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</h2></div></div></div>
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor<dt><span class="section"><a href="Bv9ARM.ch05.html#idp72445136">The Lightweight Resolver Library</a></span></dt>
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor<dt><span class="section"><a href="Bv9ARM.ch05.html#lwresd">Running a Resolver Daemon</a></span></dt>
d1a5c8385583011b8adaf259d3460c22595b4a66Ramaswamy Tummala <div class="section" title="The Lightweight Resolver Library">
d1a5c8385583011b8adaf259d3460c22595b4a66Ramaswamy Tummala<div class="titlepage"><div><div><h2 class="title" style="clear: both">
d1a5c8385583011b8adaf259d3460c22595b4a66Ramaswamy Tummala<a name="idp72445136"></a>The Lightweight Resolver Library</h2></div></div></div>
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor Traditionally applications have been linked with a stub resolver
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor library that sends recursive DNS queries to a local caching name
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor IPv6 once introduced new complexity into the resolution process,
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor such as following A6 chains and DNAME records, and simultaneous
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor lookup of IPv4 and IPv6 addresses. Though most of the complexity was
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor then removed, these are hard or impossible
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor to implement in a traditional stub resolver.
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor <acronym class="acronym">BIND</acronym> 9 therefore can also provide resolution
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor services to local clients
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor using a combination of a lightweight resolver library and a resolver
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor daemon process running on the local host. These communicate using
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor a simple UDP-based protocol, the "lightweight resolver protocol"
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor that is distinct from and simpler than the full DNS protocol.
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor <div class="section" title="Running a Resolver Daemon">
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor<div class="titlepage"><div><div><h2 class="title" style="clear: both">
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor<a name="lwresd"></a>Running a Resolver Daemon</h2></div></div></div>
d1a5c8385583011b8adaf259d3460c22595b4a66Ramaswamy Tummala To use the lightweight resolver interface, the system must
d1a5c8385583011b8adaf259d3460c22595b4a66Ramaswamy Tummala run the resolver daemon <span class="command"><strong>lwresd</strong></span> or a
d1a5c8385583011b8adaf259d3460c22595b4a66Ramaswamy Tummala name server configured with a <span class="command"><strong>lwres</strong></span>
d1a5c8385583011b8adaf259d3460c22595b4a66Ramaswamy Tummala By default, applications using the lightweight resolver library will
d1a5c8385583011b8adaf259d3460c22595b4a66Ramaswamy Tummala UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor address can be overridden by <span class="command"><strong>lwserver</strong></span>
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor The daemon currently only looks in the DNS, but in the future
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor it may use other sources such as <code class="filename">/etc/hosts</code>,
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor The <span class="command"><strong>lwresd</strong></span> daemon is essentially a
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor caching-only name server that responds to requests using the
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor resolver protocol rather than the DNS protocol. Because it needs
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor to run on each host, it is designed to require no or minimal
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor configuration.
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor Unless configured otherwise, it uses the name servers listed on
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor <span class="command"><strong>nameserver</strong></span> lines in <code class="filename">/etc/resolv.conf</code>
d1a5c8385583011b8adaf259d3460c22595b4a66Ramaswamy Tummala as forwarders, but is also capable of doing the resolution
d1a5c8385583011b8adaf259d3460c22595b4a66Ramaswamy Tummala autonomously if
d1a5c8385583011b8adaf259d3460c22595b4a66Ramaswamy Tummala none are specified.
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor The <span class="command"><strong>lwresd</strong></span> daemon may also be
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor configured with a
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor <code class="filename">named.conf</code> style configuration file,
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor <code class="filename">/etc/lwresd.conf</code> by default. A name
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor server may also
d1a5c8385583011b8adaf259d3460c22595b4a66Ramaswamy Tummala be configured to act as a lightweight resolver daemon using the
d1a5c8385583011b8adaf259d3460c22595b4a66Ramaswamy Tummala <span class="command"><strong>lwres</strong></span> statement in <code class="filename">named.conf</code>.
d1a5c8385583011b8adaf259d3460c22595b4a66Ramaswamy Tummala The number of client queries that the <span class="command"><strong>lwresd</strong></span>
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor daemon is able to serve can be set using the
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor <code class="option">lwres-tasks</code> and <code class="option">lwres-clients</code>
9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor statements in the configuration.
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9e39c5ba00a55fa05777cc94b148296af305e135Bill Taylor<td width="40%" align="right" valign="top">�Chapter�6.�<acronym class="acronym">BIND</acronym> 9 Configuration Reference</td>
d1a5c8385583011b8adaf259d3460c22595b4a66Ramaswamy Tummala<p xmlns:db="http://docbook.org/ns/docbook" style="text-align: center;">BIND 9.11.0pre-alpha</p>