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152N/A<
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acronym class="acronym">BIND</
acronym> 9 Lightweight Resolver</
h2></
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152N/A<
p><
b>Table of Contents</
b></
p>
152N/A<
dt><
span class="section"><
a href="Bv9ARM.ch05.html#idp72445136">The Lightweight Resolver Library</
a></
span></
dt>
152N/A <
div class="section" title="The Lightweight Resolver Library">
152N/A<
div class="titlepage"><
div><
div><
h2 class="title" style="clear: both">
152N/A<
a name="idp72445136"></
a>The Lightweight Resolver Library</
h2></
div></
div></
div>
152N/A Traditionally applications have been linked with a stub resolver
152N/A library that sends recursive DNS queries to a local caching name
152N/A IPv6 once introduced new complexity into the resolution process,
152N/A such as following A6 chains and DNAME records, and simultaneous
152N/A lookup of IPv4 and IPv6 addresses. Though most of the complexity was
152N/A then removed, these are hard or impossible
152N/A to implement in a traditional stub resolver.
152N/A <
acronym class="acronym">BIND</
acronym> 9 therefore can also provide resolution
152N/A services to local clients
152N/A using a combination of a lightweight resolver library and a resolver
152N/A daemon process running on the local host. These communicate using
152N/A a simple UDP-based protocol, the "lightweight resolver protocol"
152N/A that is distinct from and simpler than the full DNS protocol.
152N/A <
div class="section" title="Running a Resolver Daemon">
152N/A<
div class="titlepage"><
div><
div><
h2 class="title" style="clear: both">
152N/A<
a name="lwresd"></
a>Running a Resolver Daemon</
h2></
div></
div></
div>
152N/A To use the lightweight resolver interface, the system must
152N/A run the resolver daemon <
span class="command"><
strong>lwresd</
strong></
span> or a
152N/A name server configured with a <
span class="command"><
strong>lwres</
strong></
span>
152N/A By default, applications using the lightweight resolver library will
152N/A UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
152N/A address can be overridden by <
span class="command"><
strong>lwserver</
strong></
span>
152N/A The daemon currently only looks in the DNS, but in the future
152N/A it may use other sources such as <
code class="filename">/
etc/
hosts</
code>,
152N/A The <
span class="command"><
strong>lwresd</
strong></
span> daemon is essentially a
152N/A caching-only name server that responds to requests using the
152N/A resolver protocol rather than the DNS protocol. Because it needs
152N/A to run on each host, it is designed to require no or minimal
152N/A Unless configured otherwise, it uses the name servers listed on
152N/A <
span class="command"><
strong>nameserver</
strong></
span> lines in <
code class="filename">/
etc/
resolv.conf</
code>
152N/A as forwarders, but is also capable of doing the resolution
152N/A The <
span class="command"><
strong>lwresd</
strong></
span> daemon may also be
152N/A be configured to act as a lightweight resolver daemon using the
152N/A <
span class="command"><
strong>lwres</
strong></
span> statement in <
code class="filename">
named.conf</
code>.
152N/A The number of client queries that the <
span class="command"><
strong>lwresd</
strong></
span>
152N/A daemon is able to serve can be set using the
152N/A <
code class="option">lwres-tasks</
code> and <
code class="option">lwres-clients</
code>
152N/A statements in the configuration.
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