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ff920f8ae37ba372801b67ea7c3d5bf1dfb55585dreid<title>Chapter�5.�The BIND 9 Lightweight Resolver</title>
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998a0c99bc22357406f359ace2f602c5d6e376c6wrowe<tr><th colspan="3" align="center">Chapter�5.�The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</th></tr>
998d56ea74f8cc733b423da076dadb0fd0a789f3wrowe<a accesskey="p" href="Bv9ARM.ch04.html">Prev</a>�</td>
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998a0c99bc22357406f359ace2f602c5d6e376c6wrowe<a name="Bv9ARM.ch05"></a>Chapter�5.�The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</h1></div></div></div>
a601d863bd772fefc4dc82a883589d8be6a44811wrowe<dt><span class="section"><a href="Bv9ARM.ch05.html#id-1.6.3">The Lightweight Resolver Library</a></span></dt>
a601d863bd772fefc4dc82a883589d8be6a44811wrowe<dt><span class="section"><a href="Bv9ARM.ch05.html#lwresd">Running a Resolver Daemon</a></span></dt>
a601d863bd772fefc4dc82a883589d8be6a44811wrowe<div class="titlepage"><div><div><h2 class="title" style="clear: both">
a601d863bd772fefc4dc82a883589d8be6a44811wrowe<a name="id-1.6.3"></a>The Lightweight Resolver Library</h2></div></div></div>
fc9e01023a2fb7f7af9b25621ab080bbe7a95611jerenkrantz Traditionally applications have been linked with a stub resolver
a601d863bd772fefc4dc82a883589d8be6a44811wrowe library that sends recursive DNS queries to a local caching name
998a0c99bc22357406f359ace2f602c5d6e376c6wrowe IPv6 once introduced new complexity into the resolution process,
998a0c99bc22357406f359ace2f602c5d6e376c6wrowe such as following A6 chains and DNAME records, and simultaneous
998a0c99bc22357406f359ace2f602c5d6e376c6wrowe lookup of IPv4 and IPv6 addresses. Though most of the complexity was
998a0c99bc22357406f359ace2f602c5d6e376c6wrowe then removed, these are hard or impossible
998a0c99bc22357406f359ace2f602c5d6e376c6wrowe to implement in a traditional stub resolver.
998a0c99bc22357406f359ace2f602c5d6e376c6wrowe <acronym class="acronym">BIND</acronym> 9 therefore can also provide resolution
998a0c99bc22357406f359ace2f602c5d6e376c6wrowe services to local clients
ac901b38303d566fa40041abc9f3f9253afd6bd4brianp using a combination of a lightweight resolver library and a resolver
ac901b38303d566fa40041abc9f3f9253afd6bd4brianp daemon process running on the local host. These communicate using
ac901b38303d566fa40041abc9f3f9253afd6bd4brianp a simple UDP-based protocol, the "lightweight resolver protocol"
ac901b38303d566fa40041abc9f3f9253afd6bd4brianp that is distinct from and simpler than the full DNS protocol.
ac901b38303d566fa40041abc9f3f9253afd6bd4brianp<div class="titlepage"><div><div><h2 class="title" style="clear: both">
ac901b38303d566fa40041abc9f3f9253afd6bd4brianp<a name="lwresd"></a>Running a Resolver Daemon</h2></div></div></div>
bfae8a5d3c37df19dea49b411b109198c7e84a4fbrianp To use the lightweight resolver interface, the system must
7dfb10a15cdfd48a23a9aa5713a2deb129821761wrowe run the resolver daemon <span class="command"><strong>lwresd</strong></span> or a
998a0c99bc22357406f359ace2f602c5d6e376c6wrowe name server configured with a <span class="command"><strong>lwres</strong></span>
ac901b38303d566fa40041abc9f3f9253afd6bd4brianp By default, applications using the lightweight resolver library will
ac901b38303d566fa40041abc9f3f9253afd6bd4brianp UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
27ddebab333df2a3d82b0f4ea63878d1d9f38ae8gstein address can be overridden by <span class="command"><strong>lwserver</strong></span>
27ddebab333df2a3d82b0f4ea63878d1d9f38ae8gstein The daemon currently only looks in the DNS, but in the future
27ddebab333df2a3d82b0f4ea63878d1d9f38ae8gstein it may use other sources such as <code class="filename">/etc/hosts</code>,
27ddebab333df2a3d82b0f4ea63878d1d9f38ae8gstein The <span class="command"><strong>lwresd</strong></span> daemon is essentially a
27ddebab333df2a3d82b0f4ea63878d1d9f38ae8gstein caching-only name server that responds to requests using the
27ddebab333df2a3d82b0f4ea63878d1d9f38ae8gstein lightweight
cdc56e100a8fa11e989d1633914502db1c8e0818wrowe resolver protocol rather than the DNS protocol. Because it needs
cdc56e100a8fa11e989d1633914502db1c8e0818wrowe to run on each host, it is designed to require no or minimal
cdc56e100a8fa11e989d1633914502db1c8e0818wrowe configuration.
cdc56e100a8fa11e989d1633914502db1c8e0818wrowe Unless configured otherwise, it uses the name servers listed on
29b927351fa38aca768d31d70116acd0a71ed415jerenkrantz <span class="command"><strong>nameserver</strong></span> lines in <code class="filename">/etc/resolv.conf</code>
39d8628e74736d0bd8c4114d8e615dffa8fbbcf7gstein as forwarders, but is also capable of doing the resolution
39d8628e74736d0bd8c4114d8e615dffa8fbbcf7gstein autonomously if
39d8628e74736d0bd8c4114d8e615dffa8fbbcf7gstein none are specified.
39d8628e74736d0bd8c4114d8e615dffa8fbbcf7gstein The <span class="command"><strong>lwresd</strong></span> daemon may also be
39d8628e74736d0bd8c4114d8e615dffa8fbbcf7gstein configured with a
39d8628e74736d0bd8c4114d8e615dffa8fbbcf7gstein <code class="filename">named.conf</code> style configuration file,
39d8628e74736d0bd8c4114d8e615dffa8fbbcf7gstein <code class="filename">/etc/lwresd.conf</code> by default. A name
39d8628e74736d0bd8c4114d8e615dffa8fbbcf7gstein server may also
39d8628e74736d0bd8c4114d8e615dffa8fbbcf7gstein be configured to act as a lightweight resolver daemon using the
39d8628e74736d0bd8c4114d8e615dffa8fbbcf7gstein <span class="command"><strong>lwres</strong></span> statement in <code class="filename">named.conf</code>.
39d8628e74736d0bd8c4114d8e615dffa8fbbcf7gstein The number of client queries that the <span class="command"><strong>lwresd</strong></span>
39d8628e74736d0bd8c4114d8e615dffa8fbbcf7gstein daemon is able to serve can be set using the
39d8628e74736d0bd8c4114d8e615dffa8fbbcf7gstein <code class="option">lwres-tasks</code> and <code class="option">lwres-clients</code>
39d8628e74736d0bd8c4114d8e615dffa8fbbcf7gstein statements in the configuration.
bb16031776199a40aa54b2a6540835f7f8db0ce8jerenkrantz<a accesskey="p" href="Bv9ARM.ch04.html">Prev</a>�</td>
cdc56e100a8fa11e989d1633914502db1c8e0818wrowe<td width="40%" align="right">�<a accesskey="n" href="Bv9ARM.ch06.html">Next</a>
27ddebab333df2a3d82b0f4ea63878d1d9f38ae8gstein<td width="40%" align="left" valign="top">Chapter�4.�Advanced DNS Features�</td>
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27ddebab333df2a3d82b0f4ea63878d1d9f38ae8gstein<td width="40%" align="right" valign="top">�Chapter�6.�<acronym class="acronym">BIND</acronym> 9 Configuration Reference</td>
cdc56e100a8fa11e989d1633914502db1c8e0818wrowe<p xmlns:db="http://docbook.org/ns/docbook" style="text-align: center;">BIND 9.11.0pre-alpha</p>