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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <!-- - Copyright (C) 2000-2021 Internet Systems Consortium, Inc. ("ISC") - - This Source Code Form is subject to the terms of the Mozilla Public - License, v. 2.0. If a copy of the MPL was not distributed with this - file, You can obtain one at http://mozilla.org/MPL/2.0/. --> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Chapter�5.�The BIND 9 Lightweight Resolver</title> <meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> <link rel="home" href="Bv9ARM.html" title="BIND 9 Administrator Reference Manual"> <link rel="up" href="Bv9ARM.html" title="BIND 9 Administrator Reference Manual"> <link rel="prev" href="Bv9ARM.ch04.html" title="Chapter�4.�Advanced DNS Features"> <link rel="next" href="Bv9ARM.ch06.html" title="Chapter�6.�BIND 9 Configuration Reference"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <div class="navheader"> <table width="100%" summary="Navigation header"> <tr><th colspan="3" align="center">Chapter�5.�The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</th></tr> <tr> <td width="20%" align="left"> <a accesskey="p" href="Bv9ARM.ch04.html">Prev</a>�</td> <th width="60%" align="center">�</th> <td width="20%" align="right">�<a accesskey="n" href="Bv9ARM.ch06.html">Next</a> </td> </tr> </table> <hr> </div> <div class="chapter"> <div class="titlepage"><div><div><h1 class="title"> <a name="Bv9ARM.ch05"></a>Chapter�5.�The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</h1></div></div></div> <div class="toc"> <p><b>Table of Contents</b></p> <dl class="toc"> <dt><span class="section"><a href="Bv9ARM.ch05.html#lightweight_resolver">The Lightweight Resolver Library</a></span></dt> <dt><span class="section"><a href="Bv9ARM.ch05.html#lwresd">Running a Resolver Daemon</a></span></dt> </dl> </div> <div class="section"> <div class="titlepage"><div><div><h2 class="title" style="clear: both"> <a name="lightweight_resolver"></a>The Lightweight Resolver Library</h2></div></div></div> <p> Traditionally, applications have been linked with a stub resolver library that sends recursive DNS queries to a local caching name server. </p> <p> At first, IPv6 introduced new complexity into the resolution process, such as following A6 chains and DNAME records, and simultaneous lookup of IPv4 and IPv6 addresses. Though most of the complexity was then removed, these are hard or impossible to implement in a traditional stub resolver. </p> <p> <acronym class="acronym">BIND</acronym> 9 therefore can also provide resolution services to local clients using a combination of a lightweight resolver library and a resolver daemon process running on the local host. These communicate using a simple UDP-based protocol, the "lightweight resolver protocol," that is distinct from and simpler than the full DNS protocol. </p> </div> <div class="section"> <div class="titlepage"><div><div><h2 class="title" style="clear: both"> <a name="lwresd"></a>Running a Resolver Daemon</h2></div></div></div> <p> To use the lightweight resolver interface, the system must run the resolver daemon <span class="command"><strong>lwresd</strong></span> or a local name server configured with a <span class="command"><strong>lwres</strong></span> statement. </p> <p> By default, applications using the lightweight resolver library make UDP requests to the IPv4 loopback address (127.0.0.1) on port 921. The address can be overridden by <span class="command"><strong>lwserver</strong></span> lines in <code class="filename">/etc/resolv.conf</code>. </p> <p> The <span class="command"><strong>lwresd</strong></span> daemon is essentially a caching-only name server that responds to requests using the lightweight resolver protocol rather than the DNS protocol. Because it needs to run on each host, it is designed to require no or minimal configuration. Unless otherwise instructed, 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 autonomously if none are specified. </p> <p> The <span class="command"><strong>lwresd</strong></span> daemon may also be configured with a <code class="filename">named.conf</code>-style configuration file, in <code class="filename">/etc/lwresd.conf</code> by default. A name server may also 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>. </p> <p> The number of client queries that the <span class="command"><strong>lwresd</strong></span> daemon serves can be set using the <code class="option">lwres-tasks</code> and <code class="option">lwres-clients</code> statements in the configuration. </p> </div> </div> <div class="navfooter"> <hr> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"> <a accesskey="p" href="Bv9ARM.ch04.html">Prev</a>�</td> <td width="20%" align="center">�</td> <td width="40%" align="right">�<a accesskey="n" href="Bv9ARM.ch06.html">Next</a> </td> </tr> <tr> <td width="40%" align="left" valign="top">Chapter�4.�Advanced DNS Features�</td> <td width="20%" align="center"><a accesskey="h" href="Bv9ARM.html">Home</a></td> <td width="40%" align="right" valign="top">�Chapter�6.�<acronym class="acronym">BIND</acronym> 9 Configuration Reference</td> </tr> </table> </div> <p xmlns:db="http://docbook.org/ns/docbook" style="text-align: center;">BIND 9.11.36 (Extended Support Version)</p> </body> </html>
