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4616N/A<
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th colspan="3" align="center">Chapter�5.�The <
acronym class="acronym">BIND</
acronym> 9 Lightweight Resolver</
th></
tr>
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4616N/A<
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4616N/A<
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h1 class="title">
4616N/A<
a name="Bv9ARM.ch05"></
a>Chapter�5.�The <
acronym class="acronym">BIND</
acronym> 9 Lightweight Resolver</
h1></
div></
div></
div>
4616N/A<
p><
b>Table of Contents</
b></
p>
4616N/A<
dt><
span class="section"><
a href="Bv9ARM.ch05.html#id-1.6.3">The Lightweight Resolver Library</
a></
span></
dt>
4616N/A<
div class="titlepage"><
div><
div><
h2 class="title" style="clear: both">
4616N/A<
a name="id-1.6.3"></
a>The Lightweight Resolver Library</
h2></
div></
div></
div>
4616N/A Traditionally applications have been linked with a stub resolver
4616N/A library that sends recursive DNS queries to a local caching name
4616N/A IPv6 once introduced new complexity into the resolution process,
5047N/A such as following A6 chains and DNAME records, and simultaneous
4616N/A lookup of IPv4 and IPv6 addresses. Though most of the complexity was
4616N/A then removed, these are hard or impossible
4616N/A to implement in a traditional stub resolver.
4616N/A <
acronym class="acronym">BIND</
acronym> 9 therefore can also provide resolution
4616N/A using a combination of a lightweight resolver library and a resolver
4616N/A daemon process running on the local host. These communicate using
4616N/A a simple UDP-based protocol, the "lightweight resolver protocol"
4616N/A that is distinct from and simpler than the full DNS protocol.
4616N/A<
div class="titlepage"><
div><
div><
h2 class="title" style="clear: both">
4616N/A<
a name="lwresd"></
a>Running a Resolver Daemon</
h2></
div></
div></
div>
4616N/A To use the lightweight resolver interface, the system must
4616N/A run the resolver daemon <
span class="command"><
strong>lwresd</
strong></
span> or a
4616N/A name server configured with a <
span class="command"><
strong>lwres</
strong></
span>
4616N/A By default, applications using the lightweight resolver library will
4616N/A UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
4616N/A address can be overridden by <
span class="command"><
strong>lwserver</
strong></
span>
4616N/A The daemon currently only looks in the DNS, but in the future
4616N/A it may use other sources such as <
code class="filename">/
etc/
hosts</
code>,
4616N/A The <
span class="command"><
strong>lwresd</
strong></
span> daemon is essentially a
4616N/A caching-only name server that responds to requests using the
5047N/A resolver protocol rather than the DNS protocol. Because it needs
5047N/A to run on each host, it is designed to require no or minimal
5047N/A Unless configured otherwise, it uses the name servers listed on
5047N/A <
span class="command"><
strong>nameserver</
strong></
span> lines in <
code class="filename">/
etc/
resolv.conf</
code>
5047N/A as forwarders, but is also capable of doing the resolution
5047N/A The <
span class="command"><
strong>lwresd</
strong></
span> daemon may also be
5047N/A be configured to act as a lightweight resolver daemon using the
5061N/A <
span class="command"><
strong>lwres</
strong></
span> statement in <
code class="filename">
named.conf</
code>.
5047N/A The number of client queries that the <
span class="command"><
strong>lwresd</
strong></
span>
5047N/A daemon is able to serve can be set using the
5047N/A <
code class="option">lwres-tasks</
code> and <
code class="option">lwres-clients</
code>
5047N/A statements in the configuration.
5047N/A<
table width="100%" summary="Navigation footer">
5047N/A<
td width="40%" align="left">
5047N/A<
td width="20%" align="center">�</
td>
5047N/A<
td width="40%" align="left" valign="top">Chapter�4.�Advanced DNS Features�</
td>
5047N/A<
td width="40%" align="right" valign="top">�Chapter�6.�<
acronym class="acronym">BIND</
acronym> 9 Configuration Reference</
td>