1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
|
<!--
- Copyright (C) 2004-2013 Internet Systems Consortium, Inc. ("ISC")
- Copyright (C) 2000-2003 Internet Software Consortium.
-
- Permission to use, copy, modify, and/or distribute this software for any
- purpose with or without fee is hereby granted, provided that the above
- copyright notice and this permission notice appear in all copies.
-
- THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
- REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
- AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
- INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
- LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
- OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
- PERFORMANCE OF THIS SOFTWARE.
-->
<!-- $Id$ -->
<html>
<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 V1.71.1">
<link rel="start" 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" lang="en">
<div class="titlepage"><div><div><h2 class="title">
<a name="Bv9ARM.ch05"></a>Chapter 5. The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</h2></div></div></div>
<div class="toc">
<p><b>Table of Contents</b></p>
<dl>
<dt><span class="sect1"><a href="Bv9ARM.ch05.html#id2573163">The Lightweight Resolver Library</a></span></dt>
<dt><span class="sect1"><a href="Bv9ARM.ch05.html#lwresd">Running a Resolver Daemon</a></span></dt>
</dl>
</div>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="id2573163"></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>
IPv6 once 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="sect1" lang="en">
<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><strong class="command">lwresd</strong></span> or a
local
name server configured with a <span><strong class="command">lwres</strong></span>
statement.
</p>
<p>
By default, applications using the lightweight resolver library will
make
UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
The
address can be overridden by <span><strong class="command">lwserver</strong></span>
lines in
<code class="filename">/etc/resolv.conf</code>.
</p>
<p>
The daemon currently only looks in the DNS, but in the future
it may use other sources such as <code class="filename">/etc/hosts</code>,
NIS, etc.
</p>
<p>
The <span><strong class="command">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 configured otherwise, it uses the name servers listed on
<span><strong class="command">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><strong class="command">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><strong class="command">lwres</strong></span> statement in <code class="filename">named.conf</code>.
</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>
</body>
</html>
|
