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acronym class="acronym">BIND</
acronym> 9 Lightweight Resolver</
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h1 class="title">
493N/A<
a name="Bv9ARM.ch05"></
a>Chapter�5.�The <
acronym class="acronym">BIND</
acronym> 9 Lightweight Resolver</
h1></
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822N/A<
p><
b>Table of Contents</
b></
p>
493N/A<
dt><
span class="section"><
a href="Bv9ARM.ch05.html#lightweight_resolver">The Lightweight Resolver Library</
a></
span></
dt>
810N/A<
div class="titlepage"><
div><
div><
h2 class="title" style="clear: both">
810N/A<
a name="lightweight_resolver"></
a>The Lightweight Resolver Library</
h2></
div></
div></
div>
970N/A Traditionally applications have been linked with a stub resolver
967N/A library that sends recursive DNS queries to a local caching name
822N/A IPv6 once introduced new complexity into the resolution process,
822N/A such as following A6 chains and DNAME records, and simultaneous
1010N/A lookup of IPv4 and IPv6 addresses. Though most of the complexity was
1010N/A then removed, these are hard or impossible
810N/A to implement in a traditional stub resolver.
851N/A <
acronym class="acronym">BIND</
acronym> 9 therefore can also provide resolution
493N/A services to local clients
493N/A using a combination of a lightweight resolver library and a resolver
174N/A daemon process running on the local host. These communicate using
970N/A a simple UDP-based protocol, the "lightweight resolver protocol"
967N/A that is distinct from and simpler than the full DNS protocol.
1010N/A<
div class="titlepage"><
div><
div><
h2 class="title" style="clear: both">
1010N/A<
a name="lwresd"></
a>Running a Resolver Daemon</
h2></
div></
div></
div>
186N/A To use the lightweight resolver interface, the system must
70N/A run the resolver daemon <
span class="command"><
strong>lwresd</
strong></
span> or a
822N/A name server configured with a <
span class="command"><
strong>lwres</
strong></
span>
430N/A By default, applications using the lightweight resolver library will
98N/A UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
493N/A address can be overridden by <
span class="command"><
strong>lwserver</
strong></
span>
0N/A The daemon currently only looks in the DNS, but in the future
493N/A it may use other sources such as <
code class="filename">/
etc/
hosts</
code>,
The <
span class="command"><
strong>lwresd</
strong></
span> daemon is essentially a
caching-only name server that responds to requests using the
resolver protocol rather than the DNS protocol. Because it needs
to run on each host, it is designed to require no or minimal
Unless configured otherwise, it uses the name servers listed on
<
span class="command"><
strong>nameserver</
strong></
span> lines in <
code class="filename">/
etc/
resolv.conf</
code>
as forwarders, but is also capable of doing the resolution
The <
span class="command"><
strong>lwresd</
strong></
span> daemon may also be
<
code class="filename">
named.conf</
code> style configuration file,
be configured to act as a lightweight resolver daemon using the
<
span class="command"><
strong>lwres</
strong></
span> statement in <
code class="filename">
named.conf</
code>.
The number of client queries that the <
span class="command"><
strong>lwresd</
strong></
span>
daemon is able to serve can be set using the
<
code class="option">lwres-tasks</
code> and <
code class="option">lwres-clients</
code>
statements in the configuration.
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