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span> 9 Lightweight Resolver</
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1370N/A<
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1370N/A<
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a>Chapter�5.�The <
span class="acronym">BIND</
span> 9 Lightweight Resolver</
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1233N/A<
p><
b>Table of Contents</
b></
p>
1179N/A<
dt><
span class="sect1"><
a href="Bv9ARM.ch05.html#id2553657">The Lightweight Resolver Library</
a></
span></
dt>
1370N/A<
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1179N/A<
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h2 class="title" style="clear: both">
1179N/A<
a name="id2553657"></
a>The Lightweight Resolver Library</
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1370N/A Traditionally applications have been linked with a stub resolver
1370N/A library that sends recursive DNS queries to a local caching name
1265N/A IPv6 once introduced new complexity into the resolution process,
1370N/A such as following A6 chains and DNAME records, and simultaneous
1370N/A lookup of IPv4 and IPv6 addresses. Though most of the complexity was
1370N/A then removed, these are hard or impossible
1370N/A to implement in a traditional stub resolver.
1370N/A <
span class="acronym">BIND</
span> 9 therefore can also provide resolution
1265N/A using a combination of a lightweight resolver library and a resolver
1370N/A daemon process running on the local host. These communicate using
1370N/A a simple UDP-based protocol, the "lightweight resolver protocol"
1370N/A that is distinct from and simpler than the full DNS protocol.
1370N/A<
div class="sect1" lang="en">
1370N/A<
div class="titlepage"><
div><
div><
h2 class="title" style="clear: both">
1370N/A<
a name="lwresd"></
a>Running a Resolver Daemon</
h2></
div></
div></
div>
1370N/A To use the lightweight resolver interface, the system must
1370N/A run the resolver daemon <
span><
strong class="command">lwresd</
strong></
span> or a
1370N/A name server configured with a <
span><
strong class="command">lwres</
strong></
span>
1370N/A By default, applications using the lightweight resolver library will
1370N/A UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
1370N/A address can be overridden by <
span><
strong class="command">lwserver</
strong></
span>
341N/A The daemon currently only looks in the DNS, but in the future
341N/A it may use other sources such as <
code class="filename">/
etc/
hosts</
code>,
1339N/A The <
span><
strong class="command">lwresd</
strong></
span> daemon is essentially a
970N/A caching-only name server that responds to requests using the
970N/A resolver protocol rather than the DNS protocol. Because it needs
970N/A to run on each host, it is designed to require no or minimal
970N/A Unless configured otherwise, it uses the name servers listed on
970N/A <
span><
strong class="command">nameserver</
strong></
span> lines in <
code class="filename">/
etc/
resolv.conf</
code>
970N/A as forwarders, but is also capable of doing the resolution
970N/A The <
span><
strong class="command">lwresd</
strong></
span> daemon may also be
493N/A be configured to act as a lightweight resolver daemon using the
969N/A <
span><
strong class="command">lwres</
strong></
span> statement in <
code class="filename">
named.conf</
code>.
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1029N/A<
td width="40%" align="right" valign="top">�Chapter�6.�<
span class="acronym">BIND</
span> 9 Configuration Reference</
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