3652N/A - Copyright (C) 2004-2014 Internet Systems Consortium, Inc. ("ISC") 3998N/A - Copyright (C) 2000-2003 Internet Software Consortium. 3998N/A - Permission to use, copy, modify, and/or distribute this software for any 3998N/A - purpose with or without fee is hereby granted, provided that the above 3998N/A - copyright notice and this permission notice appear in all copies. 3998N/A - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH 3998N/A - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY 3998N/A - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, 3998N/A - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM 3998N/A - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE 3998N/A - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 3998N/A - PERFORMANCE OF THIS SOFTWARE. 3652N/A<
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acronym class="acronym">BIND</
acronym> 9 Lightweight Resolver</
th></
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div><
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h2 class="title">
4046N/A<
a name="Bv9ARM.ch05"></
a>Chapter�5.�The <
acronym class="acronym">BIND</
acronym> 9 Lightweight Resolver</
h2></
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div>
3652N/A<
p><
b>Table of Contents</
b></
p>
3652N/A<
dt><
span class="sect1"><
a href="Bv9ARM.ch05.html#id2571895">The Lightweight Resolver Library</
a></
span></
dt>
3652N/A<
div class="sect1" lang="en">
3652N/A<
div class="titlepage"><
div><
div><
h2 class="title" style="clear: both">
3652N/A<
a name="id2571895"></
a>The Lightweight Resolver Library</
h2></
div></
div></
div>
3652N/A Traditionally applications have been linked with a stub resolver
3652N/A library that sends recursive DNS queries to a local caching name
3652N/A IPv6 once introduced new complexity into the resolution process,
3998N/A such as following A6 chains and DNAME records, and simultaneous
3998N/A lookup of IPv4 and IPv6 addresses. Though most of the complexity was
3652N/A then removed, these are hard or impossible
3652N/A to implement in a traditional stub resolver.
3652N/A <
acronym class="acronym">BIND</
acronym> 9 therefore can also provide resolution
3652N/A using a combination of a lightweight resolver library and a resolver
3652N/A daemon process running on the local host. These communicate using
3652N/A a simple UDP-based protocol, the "lightweight resolver protocol"
3652N/A that is distinct from and simpler than the full DNS protocol.
3652N/A<
div class="sect1" lang="en">
3652N/A<
div class="titlepage"><
div><
div><
h2 class="title" style="clear: both">
3652N/A<
a name="lwresd"></
a>Running a Resolver Daemon</
h2></
div></
div></
div>
3652N/A To use the lightweight resolver interface, the system must
3652N/A run the resolver daemon <
span><
strong class="command">lwresd</
strong></
span> or a
3652N/A name server configured with a <
span><
strong class="command">lwres</
strong></
span>
3652N/A By default, applications using the lightweight resolver library will
3652N/A UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
3652N/A address can be overridden by <
span><
strong class="command">lwserver</
strong></
span>
3998N/A The daemon currently only looks in the DNS, but in the future
3998N/A it may use other sources such as <
code class="filename">/
etc/
hosts</
code>,
3652N/A The <
span><
strong class="command">lwresd</
strong></
span> daemon is essentially a
3652N/A caching-only name server that responds to requests using the
3652N/A resolver protocol rather than the DNS protocol. Because it needs
3652N/A to run on each host, it is designed to require no or minimal
3652N/A Unless configured otherwise, it uses the name servers listed on
3652N/A <
span><
strong class="command">nameserver</
strong></
span> lines in <
code class="filename">/
etc/
resolv.conf</
code>
3652N/A as forwarders, but is also capable of doing the resolution
3652N/A The <
span><
strong class="command">lwresd</
strong></
span> daemon may also be
3652N/A be configured to act as a lightweight resolver daemon using the
3652N/A <
span><
strong class="command">lwres</
strong></
span> statement in <
code class="filename">
named.conf</
code>.
3652N/A<
table width="100%" summary="Navigation footer">
3652N/A<
td width="40%" align="left">
3652N/A<
td width="20%" align="center">�</
td>
3652N/A<
td width="40%" align="left" valign="top">Chapter�4.�Advanced DNS Features�</
td>
3652N/A<
td width="40%" align="right" valign="top">�Chapter�6.�<
acronym class="acronym">BIND</
acronym> 9 Configuration Reference</
td>