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1910146bc46e3eee5b8668806da594107fe9aabfvboxsync<title>Chapter�5.�The BIND 9 Lightweight Resolver</title>
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453ae3ee24693b7cc05e53375f90331a8d2fad40vboxsync<tr><th colspan="3" align="center">Chapter�5.�The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</th></tr>
25a1e10563d649a2d2d4ded3a741b33b1b9c1d10vboxsync<a accesskey="p" href="Bv9ARM.ch04.html">Prev</a>�</td>
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1910146bc46e3eee5b8668806da594107fe9aabfvboxsync<a name="Bv9ARM.ch05"></a>Chapter�5.�The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</h1></div></div></div>
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync<dt><span class="section"><a href="Bv9ARM.ch05.html#id-1.6.2">The Lightweight Resolver Library</a></span></dt>
d9992886d98f1ab92fe43b15a58f75a374cb3f1evboxsync<dt><span class="section"><a href="Bv9ARM.ch05.html#lwresd">Running a Resolver Daemon</a></span></dt>
d9992886d98f1ab92fe43b15a58f75a374cb3f1evboxsync<div class="titlepage"><div><div><h2 class="title" style="clear: both">
453ae3ee24693b7cc05e53375f90331a8d2fad40vboxsync<a name="id-1.6.2"></a>The Lightweight Resolver Library</h2></div></div></div>
7ee4964086c77ff4e938e57cf71e079a979b2497vboxsync Traditionally applications have been linked with a stub resolver
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync library that sends recursive DNS queries to a local caching name
5c0a93a5d23fb128f357893b6d8c60f9ab62038fvboxsync IPv6 once introduced new complexity into the resolution process,
5c0a93a5d23fb128f357893b6d8c60f9ab62038fvboxsync such as following A6 chains and DNAME records, and simultaneous
5c0a93a5d23fb128f357893b6d8c60f9ab62038fvboxsync lookup of IPv4 and IPv6 addresses. Though most of the complexity was
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync then removed, these are hard or impossible
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync to implement in a traditional stub resolver.
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync <acronym class="acronym">BIND</acronym> 9 therefore can also provide resolution
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync services to local clients
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync using a combination of a lightweight resolver library and a resolver
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync daemon process running on the local host. These communicate using
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync a simple UDP-based protocol, the "lightweight resolver protocol"
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync that is distinct from and simpler than the full DNS protocol.
7ee4964086c77ff4e938e57cf71e079a979b2497vboxsync<div class="titlepage"><div><div><h2 class="title" style="clear: both">
7ee4964086c77ff4e938e57cf71e079a979b2497vboxsync<a name="lwresd"></a>Running a Resolver Daemon</h2></div></div></div>
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync To use the lightweight resolver interface, the system must
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync run the resolver daemon <span class="command"><strong>lwresd</strong></span> or a
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync name server configured with a <span class="command"><strong>lwres</strong></span>
9508848aea94fe052556767bbf87e1c212380a66vboxsync By default, applications using the lightweight resolver library will
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync address can be overridden by <span class="command"><strong>lwserver</strong></span>
07cd6d300c7b0a828b31d83eb0c09876dd028040vboxsync The daemon currently only looks in the DNS, but in the future
ecbaea9ad65eebbee668d1023015855b750e6505vboxsync it may use other sources such as <code class="filename">/etc/hosts</code>,
07cd6d300c7b0a828b31d83eb0c09876dd028040vboxsync The <span class="command"><strong>lwresd</strong></span> daemon is essentially a
07cd6d300c7b0a828b31d83eb0c09876dd028040vboxsync caching-only name server that responds to requests using the
07cd6d300c7b0a828b31d83eb0c09876dd028040vboxsync lightweight
07cd6d300c7b0a828b31d83eb0c09876dd028040vboxsync resolver protocol rather than the DNS protocol. Because it needs
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync to run on each host, it is designed to require no or minimal
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync configuration.
a4b605335b7e6a6ba6d5a301bc96de0e89e4b663vboxsync Unless configured otherwise, it uses the name servers listed on
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync <span class="command"><strong>nameserver</strong></span> lines in <code class="filename">/etc/resolv.conf</code>
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync as forwarders, but is also capable of doing the resolution
453ae3ee24693b7cc05e53375f90331a8d2fad40vboxsync autonomously if
453ae3ee24693b7cc05e53375f90331a8d2fad40vboxsync none are specified.
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync The <span class="command"><strong>lwresd</strong></span> daemon may also be
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync configured with a
453ae3ee24693b7cc05e53375f90331a8d2fad40vboxsync <code class="filename">named.conf</code> style configuration file,
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync <code class="filename">/etc/lwresd.conf</code> by default. A name
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync server may also
35dc60b8bbc1a1a0ba91adc45086a48f36074eb9vboxsync be configured to act as a lightweight resolver daemon using the
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync <span class="command"><strong>lwres</strong></span> statement in <code class="filename">named.conf</code>.
453ae3ee24693b7cc05e53375f90331a8d2fad40vboxsync The number of client queries that the <span class="command"><strong>lwresd</strong></span>
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync daemon is able to serve can be set using the
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync <code class="option">lwres-tasks</code> and <code class="option">lwres-clients</code>
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync statements in the configuration.
d41601138ae19f7b0060d732dbaec22ddf098fd3vboxsync<a accesskey="p" href="Bv9ARM.ch04.html">Prev</a>�</td>
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync<td width="40%" align="right">�<a accesskey="n" href="Bv9ARM.ch06.html">Next</a>
453ae3ee24693b7cc05e53375f90331a8d2fad40vboxsync<td width="40%" align="left" valign="top">Chapter�4.�Advanced DNS Features�</td>
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1910146bc46e3eee5b8668806da594107fe9aabfvboxsync<td width="40%" align="right" valign="top">�Chapter�6.�<acronym class="acronym">BIND</acronym> 9 Configuration Reference</td>
1910146bc46e3eee5b8668806da594107fe9aabfvboxsync<p xmlns:db="http://docbook.org/ns/docbook" style="text-align: center;">BIND 9.11.0pre-alpha</p>