Bv9ARM.ch05.html revision 75c0816e8295e180f4bc7f10db3d0d880383bc1c
12ea6e8d01681430f89557c24dcefdacb29d391fDav Glass - Copyright (C) 2004, 2005 Internet Systems Consortium, Inc. ("ISC")
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass - Copyright (C) 2000-2003 Internet Software Consortium.
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass - Permission to use, copy, modify, and distribute this software for any
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass - purpose with or without fee is hereby granted, provided that the above
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass - copyright notice and this permission notice appear in all copies.
046ea4d1ee0f22d956cd360e1e0c0b275aa4bbd0Dav Glass - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass - PERFORMANCE OF THIS SOFTWARE.
046ea4d1ee0f22d956cd360e1e0c0b275aa4bbd0Dav Glass<!-- $Id: Bv9ARM.ch05.html,v 1.42 2005/05/13 03:14:09 marka Exp $ -->
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<title>Chapter�5.�The BIND 9 Lightweight Resolver</title>
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<meta name="generator" content="DocBook XSL Stylesheets V1.68.1">
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<link rel="start" href="Bv9ARM.html" title="BIND 9 Administrator Reference Manual">
046ea4d1ee0f22d956cd360e1e0c0b275aa4bbd0Dav Glass<link rel="up" href="Bv9ARM.html" title="BIND 9 Administrator Reference Manual">
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<link rel="prev" href="Bv9ARM.ch04.html" title="Chapter�4.�Advanced DNS Features">
12ea6e8d01681430f89557c24dcefdacb29d391fDav Glass<link rel="next" href="Bv9ARM.ch06.html" title="Chapter�6.�BIND 9 Configuration Reference">
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<tr><th colspan="3" align="center">Chapter�5.�The <span class="acronym">BIND</span> 9 Lightweight Resolver</th></tr>
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<a accesskey="p" href="Bv9ARM.ch04.html">Prev</a>�</td>
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<td width="20%" align="right">�<a accesskey="n" href="Bv9ARM.ch06.html">Next</a>
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<div class="titlepage"><div><div><h2 class="title">
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<a name="Bv9ARM.ch05"></a>Chapter�5.�The <span class="acronym">BIND</span> 9 Lightweight Resolver</h2></div></div></div>
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<dt><span class="sect1"><a href="Bv9ARM.ch05.html#id2541418">The Lightweight Resolver Library</a></span></dt>
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<dt><span class="sect1"><a href="Bv9ARM.ch05.html#lwresd">Running a Resolver Daemon</a></span></dt>
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<div class="titlepage"><div><div><h2 class="title" style="clear: both">
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<a name="id2541418"></a>The Lightweight Resolver Library</h2></div></div></div>
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass Traditionally applications have been linked with a stub resolver
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass library that sends recursive DNS queries to a local caching name
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass IPv6 once introduced new complexity into the resolution process,
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass such as following A6 chains and DNAME records, and simultaneous
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass lookup of IPv4 and IPv6 addresses. Though most of the complexity was
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass then removed, these are hard or impossible
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass to implement in a traditional stub resolver.
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass Instead, <span class="acronym">BIND</span> 9 provides resolution
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass services to local clients
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass using a combination of a lightweight resolver library and a resolver
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass daemon process running on the local host. These communicate using
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass a simple UDP-based protocol, the "lightweight resolver protocol"
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass that is distinct from and simpler than the full DNS protocol.
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<div class="titlepage"><div><div><h2 class="title" style="clear: both">
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<a name="lwresd"></a>Running a Resolver Daemon</h2></div></div></div>
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass To use the lightweight resolver interface, the system must
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass run the resolver daemon <span><strong class="command">lwresd</strong></span> or a
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass name server configured with a <span><strong class="command">lwres</strong></span>
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass By default, applications using the lightweight resolver library will
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass address can be overridden by <span><strong class="command">lwserver</strong></span>
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass The daemon currently only looks in the DNS, but in the future
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass it may use other sources such as <code class="filename">/etc/hosts</code>,
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass The <span><strong class="command">lwresd</strong></span> daemon is essentially a
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass caching-only name server that responds to requests using the
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass resolver protocol rather than the DNS protocol. Because it needs
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass to run on each host, it is designed to require no or minimal
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass configuration.
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass Unless configured otherwise, it uses the name servers listed on
046ea4d1ee0f22d956cd360e1e0c0b275aa4bbd0Dav Glass <span><strong class="command">nameserver</strong></span> lines in <code class="filename">/etc/resolv.conf</code>
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass as forwarders, but is also capable of doing the resolution
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass autonomously if
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass none are specified.
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass The <span><strong class="command">lwresd</strong></span> daemon may also be
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass configured with a
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass <code class="filename">named.conf</code> style configuration file,
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass <code class="filename">/etc/lwresd.conf</code> by default. A name
046ea4d1ee0f22d956cd360e1e0c0b275aa4bbd0Dav Glass server may also
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass be configured to act as a lightweight resolver daemon using the
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass <span><strong class="command">lwres</strong></span> statement in <code class="filename">named.conf</code>.
046ea4d1ee0f22d956cd360e1e0c0b275aa4bbd0Dav Glass<a accesskey="p" href="Bv9ARM.ch04.html">Prev</a>�</td>
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<td width="40%" align="right">�<a accesskey="n" href="Bv9ARM.ch06.html">Next</a>
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<td width="40%" align="left" valign="top">Chapter�4.�Advanced DNS Features�</td>
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<td width="20%" align="center"><a accesskey="h" href="Bv9ARM.html">Home</a></td>
4613cfd8960e141ac5d088a10bc6124df2e46f24Dav Glass<td width="40%" align="right" valign="top">�Chapter�6.�<span class="acronym">BIND</span> 9 Configuration Reference</td>