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<B> Next:</B> <A NAME="tex2html2767"
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<A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></A>
<UL>
<LI><A NAME="tex2html2768"
HREF="#SECTION004310000000000000000">40.1 Documentation</A>
<LI><A NAME="tex2html2769"
HREF="#SECTION004320000000000000000">40.2 Configuring <TT>
<FONT COLOR="#0000ff">bind</FONT></TT></A>
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<LI><A NAME="tex2html2770"
HREF="#SECTION004321000000000000000">40.2.1 Example configuration</A>
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<LI><A NAME="tex2html2771"
HREF="#SECTION004321100000000000000"><IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>Local client configuration:</I> <TT>
<FONT COLOR="#0000ff">/etc/resolv.conf</FONT></TT></A>
<LI><A NAME="tex2html2772"
HREF="#SECTION004321200000000000000"><IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>Top-level config file:</I> <TT>
<FONT COLOR="#0000ff">/etc/named.conf</FONT></TT></A>
<LI><A NAME="tex2html2773"
HREF="#SECTION004321300000000000000"><IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>Root name server list:</I> <TT>
<FONT COLOR="#0000ff">/var/named/named.ca</FONT></TT></A>
<LI><A NAME="tex2html2774"
HREF="#SECTION004321400000000000000"><IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>Local forward lookups:</I> <TT>
<FONT COLOR="#0000ff">/var/named/named.localdomain</FONT></TT></A>
<LI><A NAME="tex2html2775"
HREF="#SECTION004321500000000000000"><IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>Local reverse lookups:</I> <TT>
<FONT COLOR="#0000ff">/var/named/named.127.0.0.1</FONT></TT></A>
<LI><A NAME="tex2html2776"
HREF="#SECTION004321600000000000000"><IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>Authoritative domain file:</I> <TT>
<FONT COLOR="#0000ff">/var/named/named.cranzgot.co.za</FONT></TT></A>
<LI><A NAME="tex2html2777"
HREF="#SECTION004321700000000000000"><IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>LAN reverse lookups:</I> <TT>
<FONT COLOR="#0000ff">/var/named/named.192.168.2</FONT></TT></A>
<LI><A NAME="tex2html2778"
HREF="#SECTION004321800000000000000"><IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>Authoritative reverse lookups (1):</I> <TT>
<FONT COLOR="#0000ff">/var/named/named.196.28.144</FONT></TT></A>
<LI><A NAME="tex2html2779"
HREF="#SECTION004321900000000000000"><IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>Authoritative reverse lookups (2):</I> <TT>
<FONT COLOR="#0000ff">/var/named/named.160.123.181.44</FONT></TT></A>
</UL>
<LI><A NAME="tex2html2780"
HREF="#SECTION004322000000000000000">40.2.2 Starting the name server</A>
<LI><A NAME="tex2html2781"
HREF="#SECTION004323000000000000000">40.2.3 Configuration in detail</A>
<UL>
<LI><A NAME="tex2html2782"
HREF="#SECTION004323100000000000000">40.2.3.1 Top-level <TT>
<FONT COLOR="#0000ff">named.conf</FONT></TT></A>
<LI><A NAME="tex2html2783"
HREF="#SECTION004323200000000000000">40.2.3.2 Domain <TT>
<FONT COLOR="#0000ff">SOA</FONT></TT> records</A>
<LI><A NAME="tex2html2784"
HREF="#SECTION004323300000000000000">40.2.3.3 Dotted and non-dotted host names</A>
<LI><A NAME="tex2html2785"
HREF="#SECTION004323400000000000000">40.2.3.4 Empty host names</A>
<LI><A NAME="tex2html2786"
HREF="#SECTION004323500000000000000">40.2.3.5 <TT>
<FONT COLOR="#0000ff">NS</FONT></TT>, <TT>
<FONT COLOR="#0000ff">MX</FONT></TT>, <TT>
<FONT COLOR="#0000ff">PTR</FONT></TT>, <TT>
<FONT COLOR="#0000ff">A</FONT></TT>, and <TT>
<FONT COLOR="#0000ff">CNAME</FONT></TT> records</A>
<LI><A NAME="tex2html2787"
HREF="#SECTION004323600000000000000">40.2.3.6 Reverse lookups configuration</A>
</UL>
</UL>
<LI><A NAME="tex2html2788"
HREF="#SECTION004330000000000000000">40.3 Round-Robin Load-Sharing</A>
<LI><A NAME="tex2html2789"
HREF="#SECTION004340000000000000000">40.4 Configuring <TT>
<FONT COLOR="#0000ff">named</FONT></TT> for Dialup Use</A>
<UL>
<LI><A NAME="tex2html2790"
HREF="#SECTION004341000000000000000">40.4.1 Example caching name server</A>
<LI><A NAME="tex2html2791"
HREF="#SECTION004342000000000000000">40.4.2 Dynamic IP addresses</A>
</UL>
<LI><A NAME="tex2html2792"
HREF="#SECTION004350000000000000000">40.5 Secondary or Slave DNS Servers</A>
</UL>
<!--End of Table of Child-Links-->
<HR>
<H1><A NAME="SECTION004300000000000000000">
40. <TT>
<FONT COLOR="#0000ff">named</FONT></TT> -- Domain Name Server</A>
</H1>
<P>
<A NAME="chap:name"></A>
<P>
In Chapter <A HREF="node30.html#chap:dns">27</A> we dealt with the ``client'' side of DNS.
In this chapter we configure the name server that services such requests.
<P>
There seems to be a lot of hype that elevates the name server to
something mystical and illusive. In fact, setting up a name server
is a standard and trivial exercise. A name server daemon is also no
heavyweight service: The <TT>
<FONT COLOR="#0000ff">named</FONT></TT> executable is 500 KB and
consumes little CPU.
<P>
The package that the name server comes in is called
<TT>
<FONT COLOR="#0000ff">bind</FONT></TT>. This chapter assumes a <TT>
<FONT COLOR="#0000ff">bind</FONT></TT> of
approximately <TT>
<FONT COLOR="#0000ff">bind-8.2</FONT></TT> or later. <TT>
<FONT COLOR="#0000ff">bind</FONT></TT>
stands for <I>Berkeley Internet Name Domain</I>.
<P>
The difficulty with setting up a name server is that the
configuration files are impossible to construct from the
specification without some kind of typing error being made.
The solution is quite simple: <I>Never</I> create a
name server config file from scratch. <I>Always</I> copy
one from an existing working name server. Here we
give more example configuration files than explanation.
You can copy these examples to create your own name server.
<P>
Please note before running <TT>
<FONT COLOR="#0000ff">bind</FONT></TT> that it has security
vulnerabilities. Hence, it may be possible for someone to hack your
machine if you are running an old version. Many people are also skeptical
about even the latest versions of <TT>
<FONT COLOR="#0000ff">bind</FONT></TT> (9.1 at the time of
writing) even though no security holes had been announced for this version.
An alternative is <TT>
<FONT COLOR="#0000ff">djbdns</FONT></TT>, which
is purported to be the ultimate DNS server.
<P>
Before you even start working on name server configuration,
you should start a new terminal window with the
command (Debian alternative in parentheses):
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>tail -f /var/log/messages</code><br>
<code>( tail -f /var/log/syslog )</code><br>
</FONT></TD></TR></TABLE><P>
Keep this window throughout the entire setup and testing
procedure. From now on, when I refer to <I>message</I>s,
I am referring to a message in this window.
<P>
<H1><A NAME="SECTION004310000000000000000">
40.1 Documentation</A>
</H1>
<P>
The man pages for <TT>
<FONT COLOR="#0000ff">named</FONT></TT>
are <TT>
<FONT COLOR="#0000ff">hostname</FONT></TT>(7),
<TT>
<FONT COLOR="#0000ff">named-xfer</FONT></TT>(8),
<TT>
<FONT COLOR="#0000ff">named</FONT></TT>(8), and <TT>
<FONT COLOR="#0000ff">ndc</FONT></TT>(8). These
pages reference a document called the
``Name Server Operations Guide for BIND.'' What they actually mean is the
PostScript file <TT>
<FONT COLOR="#0000ff">/usr/[share/]doc/bind-<version>/bog/file.psf</FONT></TT>
(or <TT>
<FONT COLOR="#0000ff">/usr/share/doc/bind/bog.ps</FONT></TT>).
<P>
The problem with some of this documentation is that it is still
based on the old (now deprecated) <TT>
<FONT COLOR="#0000ff">named.boot</FONT></TT>
configuration file. There is a script
<TT>
<FONT COLOR="#0000ff">/usr/doc/bind-<version>/named-bootconf/named-bootconf</FONT></TT>
(or <TT>
<FONT COLOR="#0000ff">/usr/sbin/named-bootconf</FONT></TT>) that reads a <TT>
<FONT COLOR="#0000ff">named.boot</FONT></TT>
file from stdin and writes a <TT>
<FONT COLOR="#0000ff">named.conf</FONT></TT> file to stdout.
I found it useful to <TT>
<FONT COLOR="#0000ff">echo "old config line" |
named-bootconf</FONT></TT> to see what a new style equivalent would be.
<P>
The directory <TT>
<FONT COLOR="#0000ff">/usr/[share/]doc/bind[-<version>]/html/</FONT></TT><A NAME="page:binddocu"></A>contains the most important general information. It is
a complete reference to <TT>
<FONT COLOR="#0000ff">bind</FONT></TT> configuration.
Parallel directories also contain FAQ documents
and various theses on security. A file <TT>
<FONT COLOR="#0000ff">style.txt</FONT></TT>
contains the recommended layout of the configuration files
for consistent spacing and readability. Finally an <TT>
<FONT COLOR="#0000ff">rfc/</FONT></TT>
directory contains the relevant RFCs (see Section <A HREF="node16.html#sec:rfc">13.6</A>).
<P>
<H1><A NAME="SECTION004320000000000000000">
40.2 Configuring <TT>
<FONT COLOR="#0000ff">bind</FONT></TT></A>
</H1>
<P>
There is only one main configuration file for <TT>
<FONT COLOR="#0000ff">named</FONT></TT>:
<TT>
<FONT COLOR="#0000ff">/etc/named.conf</FONT></TT> (or <TT>
<FONT COLOR="#0000ff">/etc/bind/named.conf</FONT></TT> on Debian--here
we assume a <TT>
<FONT COLOR="#0000ff">/etc/named.conf</FONT></TT> file for simplicity).
The <TT>
<FONT COLOR="#0000ff">named</FONT></TT> service once used a file
<TT>
<FONT COLOR="#0000ff">/etc/named.boot</FONT></TT>, but this has been scrapped. If there
is a <TT>
<FONT COLOR="#0000ff">named.boot</FONT></TT> file in your <TT>
<FONT COLOR="#0000ff">/etc</FONT></TT> directory, then it
is not being used, except possibly by a very old version of
<TT>
<FONT COLOR="#0000ff">bind</FONT></TT>.
<P>
Here we will show example configurations necessary for typical
scenarios of a name server.
<P>
<H2><A NAME="SECTION004321000000000000000">
40.2.1 Example configuration</A>
</H2>
<P>
The <TT>
<FONT COLOR="#0000ff">named.conf</FONT></TT> file will have in it the line <TT>
<FONT COLOR="#0000ff">directory
"/var/named";</FONT></TT> (or <TT>
<FONT COLOR="#0000ff">directory "/etc/named";</FONT></TT> or <TT>
<FONT COLOR="#0000ff">directory "/var/cache/bind";</FONT></TT>).
This directory holds various files containing textual lists of the name to IP address
mappings that <TT>
<FONT COLOR="#0000ff">bind</FONT></TT> will serve.
The following example is a name server for a company that has been
given a range of IP addresses <TT>
<FONT COLOR="#0000ff">196.28.144.16/29</FONT></TT> (i.e., <TT>
<FONT COLOR="#0000ff">196.28.144.16</FONT></TT>-<TT>
<FONT COLOR="#0000ff">23</FONT></TT>),
as well as one single IP address (<TT>
<FONT COLOR="#0000ff">160.123.181.44</FONT></TT>). This
example also must support a range of internal IP addresses
(<TT>
<FONT COLOR="#0000ff">192.168.2.0</FONT></TT>-<TT>
<FONT COLOR="#0000ff">255</FONT></TT>) The trick is not to think about
how everything works. If you just copy and edit things in a
consistent fashion, carefully reading the comments, <TT>
<FONT COLOR="#0000ff">bind</FONT></TT> will
work fine. I will now list all necessary files.
<P>
<H3><A NAME="SECTION004321100000000000000">
<IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>Local client configuration:</I> <TT>
<FONT COLOR="#0000ff">/etc/resolv.conf</FONT></TT></A>
</H3>
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red size="-1">
<code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue size="-1">
<code>domain localdomain</code><br>
<code>nameserver 127.0.0.1</code><br>
</FONT></TD></TR></TABLE><P>
<P>
<H3><A NAME="SECTION004321200000000000000">
<IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>Top-level config file:</I> <TT>
<FONT COLOR="#0000ff">/etc/named.conf</FONT></TT></A>
</H3>
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red size="-1">
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>5</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>10</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>15</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>20</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>25</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>30</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>35</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>40</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>45</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>50</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>55</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue size="-1">
<code>/*</code><br>
<code> * The ``directory'' line tells named that any further file name's</code><br>
<code> * given are under the /var/named/ directory.</code><br>
<code> */</code><br>
<code>options {</code><br>
<code> directory "/var/named";</code><br>
<code> /*</code><br>
<code> * If there is a firewall between you and nameservers you want</code><br>
<code> * to talk to, you might need to uncomment the query-source</code><br>
<code> * directive below. Previous versions of BIND always asked</code><br>
<code> * questions using port 53, but BIND 8.1 uses an unprivileged</code><br>
<code> * port by default.</code><br>
<code> */</code><br>
<code> // query-source address * port 53;</code><br>
<code>};</code><br>
<code> </code><br>
<code>/* The list of root servers: */</code><br>
<code>zone "." {</code><br>
<code> type hint;</code><br>
<code> file "named.ca";</code><br>
<code>};</code><br>
<code> </code><br>
<code>/* Forward lookups of the localhost: */</code><br>
<code>zone "localdomain" {</code><br>
<code> type master;</code><br>
<code> file "named.localdomain";</code><br>
<code>};</code><br>
<code> </code><br>
<code>/* Reverse lookups of the localhost: */</code><br>
<code>zone "1.0.0.127.in-addr.arpa" {</code><br>
<code> type master;</code><br>
<code> file "named.127.0.0.1";</code><br>
<code>};</code><br>
<code> </code><br>
<code>/* Forward lookups of hosts in my domain: */</code><br>
<code>zone "cranzgot.co.za" {</code><br>
<code> type master;</code><br>
<code> file "named.cranzgot.co.za";</code><br>
<code>};</code><br>
<code> </code><br>
<code>/* Reverse lookups of local IP numbers: */</code><br>
<code>zone "2.168.192.in-addr.arpa" {</code><br>
<code> type master;</code><br>
<code> file "named.192.168.2";</code><br>
<code>};</code><br>
<code> </code><br>
<code>/* Reverse lookups of 196.28.144.* Internet IP numbers: */</code><br>
<code>zone "144.28.196.in-addr.arpa" {</code><br>
<code> type master;</code><br>
<code> file "named.196.28.144";</code><br>
<code>};</code><br>
<code> </code><br>
<code>/* Reverse lookup of 160.123.181.44 only: */</code><br>
<code>zone "44.181.123.160.in-addr.arpa" {</code><br>
<code> type master;</code><br>
<code> file "named.160.123.181.44";</code><br>
<code>};</code><br>
</FONT></TD></TR></TABLE><P>
<P>
<H3><A NAME="SECTION004321300000000000000">
<IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>Root name server list:</I> <TT>
<FONT COLOR="#0000ff">/var/named/named.ca</FONT></TT></A>
</H3>
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red size="-1">
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>5</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>10</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>15</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>20</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>25</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue size="-1">
<code>; Get the original of this file from ftp://ftp.rs.internic.net/domain/named.root</code><br>
<code>;</code><br>
<code>; formerly ns.internic.net</code><br>
<code>. 3600000 IN NS a.root-servers.net.</code><br>
<code>a.root-servers.net. 3600000 A 198.41.0.4</code><br>
<code>. 3600000 NS b.root-servers.net.</code><br>
<code>b.root-servers.net. 3600000 A 128.9.0.107</code><br>
<code>. 3600000 NS c.root-servers.net.</code><br>
<code>c.root-servers.net. 3600000 A 192.33.4.12</code><br>
<code>. 3600000 NS d.root-servers.net.</code><br>
<code>d.root-servers.net. 3600000 A 128.8.10.90</code><br>
<code>. 3600000 NS e.root-servers.net.</code><br>
<code>e.root-servers.net. 3600000 A 192.203.230.10</code><br>
<code>. 3600000 NS f.root-servers.net.</code><br>
<code>f.root-servers.net. 3600000 A 192.5.5.241</code><br>
<code>. 3600000 NS g.root-servers.net.</code><br>
<code>g.root-servers.net. 3600000 A 192.112.36.4</code><br>
<code>. 3600000 NS h.root-servers.net.</code><br>
<code>h.root-servers.net. 3600000 A 128.63.2.53</code><br>
<code>. 3600000 NS i.root-servers.net.</code><br>
<code>i.root-servers.net. 3600000 A 192.36.148.17</code><br>
<code>. 3600000 NS j.root-servers.net.</code><br>
<code>j.root-servers.net. 3600000 A 198.41.0.10</code><br>
<code>. 3600000 NS k.root-servers.net.</code><br>
<code>k.root-servers.net. 3600000 A 193.0.14.129 </code><br>
<code>. 3600000 NS l.root-servers.net.</code><br>
<code>l.root-servers.net. 3600000 A 198.32.64.12</code><br>
<code>. 3600000 NS m.root-servers.net.</code><br>
<code>m.root-servers.net. 3600000 A 202.12.27.33</code><br>
</FONT></TD></TR></TABLE><P>
<P>
<H3><A NAME="SECTION004321400000000000000">
<IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>Local forward lookups:</I> <TT>
<FONT COLOR="#0000ff">/var/named/named.localdomain</FONT></TT></A>
</H3>
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red size="-1">
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>5</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>10</code></font><code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue size="-1">
<code>$TTL 259200</code><br>
<code>@ IN SOA localhost.localdomain. dns-admin.localhost.localdomain. (</code><br>
<code> 2000012101 ; Serial number</code><br>
<code> 10800 ; Refresh every 3 hours</code><br>
<code> 3600 ; Retry every hour</code><br>
<code> 3600000 ; Expire after 42 days</code><br>
<code> 259200 ) ; Minimum Time to Live (TTL) of 3 days</code><br>
<code> </code><br>
<code> IN NS localhost.localdomain.</code><br>
<code> </code><br>
<code>localhost IN A 127.0.0.1</code><br>
</FONT></TD></TR></TABLE><P>
<P>
<H3><A NAME="SECTION004321500000000000000">
<IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>Local reverse lookups:</I> <TT>
<FONT COLOR="#0000ff">/var/named/named.127.0.0.1</FONT></TT></A>
</H3>
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red size="-1">
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>5</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>10</code></font><code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue size="-1">
<code>$TTL 259200</code><br>
<code>@ IN SOA localhost. dns-admin.localhost. (</code><br>
<code> 2000012101 ; Serial number</code><br>
<code> 10800 ; Refresh every 3 hours</code><br>
<code> 3600 ; Retry every hour</code><br>
<code> 3600000 ; Expire after 42 days</code><br>
<code> 259200 ) ; Minimum Time to Live (TTL) of 3 days</code><br>
<code> </code><br>
<code> IN NS localhost.</code><br>
<code> </code><br>
<code> IN PTR localhost.</code><br>
</FONT></TD></TR></TABLE><P>
<P>
<H3><A NAME="SECTION004321600000000000000">
<IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>Authoritative domain file:</I> <TT>
<FONT COLOR="#0000ff">/var/named/named.cranzgot.co.za</FONT></TT></A>
</H3>
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red size="-1">
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>5</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>10</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>15</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>20</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>25</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>30</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>35</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>40</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>45</code></font><code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue size="-1">
<code>$TTL 259200</code><br>
<code>@ IN SOA ns1.cranzgot.co.za. dns-admin.ns1.cranzgot.co.za. (</code><br>
<code> 2000012101 ; Serial number</code><br>
<code> 10800 ; Refresh every 3 hours</code><br>
<code> 3600 ; Retry every hour</code><br>
<code> 3600000 ; Expire after 42 days</code><br>
<code> 259200 ) ; Minimum Time to Live (TTL) of 3 days</code><br>
<code> </code><br>
<code> IN NS ns1.cranzgot.co.za.</code><br>
<code> IN NS ns2.cranzgot.co.za.</code><br>
<code> </code><br>
<code> IN A 160.123.181.44</code><br>
<code> IN MX 10 mail1.cranzgot.co.za.</code><br>
<code> IN MX 20 mail2.cranzgot.co.za.</code><br>
<code> </code><br>
<code>; We will use the first IP address for the name server itself:</code><br>
<code>ns1 IN A 196.28.144.16</code><br>
<code> </code><br>
<code>; our backup name server is faaar away:</code><br>
<code>ns2 IN A 146.143.21.88</code><br>
<code> </code><br>
<code>; FTP server:</code><br>
<code>ftp IN A 196.28.144.17</code><br>
<code> </code><br>
<code>; Aliases:</code><br>
<code>www IN CNAME cranzgot.co.za.</code><br>
<code>mail1 IN CNAME ns1.cranzgot.co.za.</code><br>
<code>mail2 IN CNAME ns2.cranzgot.co.za.</code><br>
<code>gopher IN CNAME ftp.cranzgot.co.za.</code><br>
<code>pop IN CNAME mail1.cranzgot.co.za.</code><br>
<code>proxy IN CNAME ftp.cranzgot.co.za.</code><br>
<code> </code><br>
<code>; Reserved for future web servers:</code><br>
<code>unused18 IN A 196.28.144.18</code><br>
<code>unused19 IN A 196.28.144.19</code><br>
<code>unused20 IN A 196.28.144.20</code><br>
<code>unused21 IN A 196.28.144.21</code><br>
<code>unused22 IN A 196.28.144.22</code><br>
<code>unused23 IN A 196.28.144.23</code><br>
<code> </code><br>
<code>; local LAN:</code><br>
<code>pc1 IN A 192.168.2.1</code><br>
<code>pc2 IN A 192.168.2.2</code><br>
<code>pc3 IN A 192.168.2.3</code><br>
<code>pc4 IN A 192.168.2.4</code><br>
<code>; and so on... to 192.168.2.255</code><br>
</FONT></TD></TR></TABLE><P>
<P>
<H3><A NAME="SECTION004321700000000000000">
<IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>LAN reverse lookups:</I> <TT>
<FONT COLOR="#0000ff">/var/named/named.192.168.2</FONT></TT></A>
</H3>
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red size="-1">
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>5</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>10</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>15</code></font><code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue size="-1">
<code>$TTL 259200</code><br>
<code>@ IN SOA ns1.cranzgot.co.za. dns-admin.ns1.cranzgot.co.za. (</code><br>
<code> 2000012101 ; Serial number</code><br>
<code> 10800 ; Refresh every 3 hours</code><br>
<code> 3600 ; Retry every hour</code><br>
<code> 3600000 ; Expire after 42 days</code><br>
<code> 259200 ) ; Minimum Time to Live (TTL) of 3 days</code><br>
<code> </code><br>
<code> IN NS ns1.cranzgot.co.za.</code><br>
<code> </code><br>
<code>1 IN PTR pc1.cranzgot.co.za.</code><br>
<code>2 IN PTR pc2.cranzgot.co.za.</code><br>
<code>3 IN PTR pc3.cranzgot.co.za.</code><br>
<code>4 IN PTR pc4.cranzgot.co.za.</code><br>
<code>; and so on... to 255</code><br>
</FONT></TD></TR></TABLE><P>
<P>
<H3><A NAME="SECTION004321800000000000000">
<IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>Authoritative reverse lookups (1):</I> <TT>
<FONT COLOR="#0000ff">/var/named/named.196.28.144</FONT></TT></A>
</H3>
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red size="-1">
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>5</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>10</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>15</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>20</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>25</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>30</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>35</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>40</code></font><code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue size="-1">
<code>$TTL 259200</code><br>
<code>@ IN SOA ns1.cranzgot.co.za. dns-admin.ns1.cranzgot.co.za. (</code><br>
<code> 2000012101 ; Serial number</code><br>
<code> 10800 ; Refresh every 3 hours</code><br>
<code> 3600 ; Retry every hour</code><br>
<code> 3600000 ; Expire after 42 days</code><br>
<code> 259200 ) ; Minimum Time to Live (TTL) of 3 days</code><br>
<code> </code><br>
<code> IN NS dns.big-isp.net.</code><br>
<code> </code><br>
<code>0 IN NS dns.big-isp.net.</code><br>
<code>1 IN NS dns.big-isp.net.</code><br>
<code>2 IN NS dns.big-isp.net.</code><br>
<code>3 IN NS dns.big-isp.net.</code><br>
<code>4 IN NS dns.big-isp.net.</code><br>
<code>5 IN NS dns.big-isp.net.</code><br>
<code>6 IN NS dns.big-isp.net.</code><br>
<code>7 IN NS dns.big-isp.net.</code><br>
<code>8 IN NS dns.big-isp.net.</code><br>
<code>9 IN NS dns.big-isp.net.</code><br>
<code>10 IN NS dns.big-isp.net.</code><br>
<code>11 IN NS dns.big-isp.net.</code><br>
<code>12 IN NS dns.big-isp.net.</code><br>
<code>13 IN NS dns.big-isp.net.</code><br>
<code>14 IN NS dns.big-isp.net.</code><br>
<code>15 IN NS dns.big-isp.net.</code><br>
<code> </code><br>
<code>16 IN PTR ns1.cranzgot.co.za.</code><br>
<code>17 IN PTR ftp.cranzgot.co.za.</code><br>
<code>18 IN PTR unused18.cranzgot.co.za.</code><br>
<code>19 IN PTR unused19.cranzgot.co.za.</code><br>
<code>20 IN PTR unused20.cranzgot.co.za.</code><br>
<code>21 IN PTR unused21.cranzgot.co.za.</code><br>
<code>22 IN PTR unused22.cranzgot.co.za.</code><br>
<code>23 IN PTR unused23.cranzgot.co.za.</code><br>
<code> </code><br>
<code>24 IN NS dns.big-isp.net.</code><br>
<code>25 IN NS dns.big-isp.net.</code><br>
<code>26 IN NS dns.big-isp.net.</code><br>
<code>; and so on... up to 255</code><br>
</FONT></TD></TR></TABLE><P>
<P>
<H3><A NAME="SECTION004321900000000000000">
<IMG ALIGN=ABSMIDDLE BORDER=0 SRC="bullet.png"> <I>Authoritative reverse lookups (2):</I> <TT>
<FONT COLOR="#0000ff">/var/named/named.160.123.181.44</FONT></TT></A>
</H3>
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red size="-1">
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>5</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>10</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue size="-1">
<code>$TTL 259200</code><br>
<code>@ IN SOA ns1.cranzgot.co.za. dns-admin.ns1.cranzgot.co.za. (</code><br>
<code> 2000012101 ; Serial number</code><br>
<code> 10800 ; Refresh every 3 hours</code><br>
<code> 3600 ; Retry every hour</code><br>
<code> 3600000 ; Expire after 42 days</code><br>
<code> 259200 ) ; Minimum Time to Live (TTL) of 3 days</code><br>
<code> </code><br>
<code> IN NS ns1.cranzgot.co.za.</code><br>
<code> IN NS ns2.cranzgot.co.za.</code><br>
<code> </code><br>
<code> IN PTR cranzgot.co.za.</code><br>
</FONT></TD></TR></TABLE><P>
<P>
<H2><A NAME="SECTION004322000000000000000">
40.2.2 Starting the name server</A>
</H2>
<P>
If you have created a configuration similar to that above, you
can then run the <TT>
<FONT COLOR="#0000ff">bind</FONT></TT> package initialization commands.
The actions available are (alternative commands in parentheses):
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-1"><code>5</code></font><code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>/etc/rc.d/init.d/named start</code><br>
<code>( /etc/init.d/named start )</code><br>
<code>( /etc/init.d/bind start )</code><br>
<code>/etc/rc.d/init.d/named stop</code><br>
<code>/etc/rc.d/init.d/named restart</code><br>
<code>/etc/rc.d/init.d/named status</code><br>
</FONT></TD></TR></TABLE><P>
<P>
You should get messages like:
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red size="-1">
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>5</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>10</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>15</code></font><code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue size="-1">
<code>Jul 8 15:45:23 ns1 named[17656]: starting. named 8.2.2-P5 Sat Aug 5 13:21:24 EDT 2000 ^I</code><br>
<code>Jul 8 15:45:23 ns1 named[17656]: hint zone "" (IN) loaded (serial 0)</code><br>
<code>Jul 8 15:45:23 ns1 named[17656]: master zone "localhost" (IN) loaded (serial 2000012101)</code><br>
<code>Jul 8 15:45:23 ns1 named[17656]: master zone "1.0.0.127.in-addr.arpa" (IN) loaded (serial </code><br>
<code>Jul 8 15:45:23 ns1 named[17656]: master zone "cranzgot.co.za" (IN) loaded (serial 20000121</code><br>
<code>Jul 8 15:45:23 ns1 named[17656]: master zone "myisp.co.za" (IN) loaded (serial 2000012101)</code><br>
<code>Jul 8 15:45:23 ns1 named[17656]: master zone "2.168.192.in-addr.arpa" (IN) loaded (serial </code><br>
<code>Jul 8 15:45:23 ns1 named[17656]: master zone "144.28.196.in-addr.arpa" (IN) loaded (serial</code><br>
<code>Jul 8 15:45:23 ns1 named[17656]: master zone "44.181.123.160.in-addr.arpa" (IN) loaded (se</code><br>
<code>Jul 8 15:45:23 ns1 named[17656]: listening on [127.0.0.1].53 (lo)</code><br>
<code>Jul 8 15:45:23 ns1 named[17656]: listening on [196.28.144.16].53 (eth0)</code><br>
<code>Jul 8 15:45:23 ns1 named[17656]: Forwarding source address is [0.0.0.0].1041</code><br>
<code>Jul 8 15:45:23 ns1 named: named startup succeeded</code><br>
<code>Jul 8 15:45:23 ns1 named[17657]: group = 25</code><br>
<code>Jul 8 15:45:23 ns1 named[17657]: user = named</code><br>
<code>Jul 8 15:45:23 ns1 named[17657]: Ready to answer queries.</code><br>
</FONT></TD></TR></TABLE><P>
<P>
If you have made typing errors, or named files incorrectly,
you will get appropriate error messages. <I>Novice
administrators are wont to edit <TT>
<FONT COLOR="#0000ff">named</FONT></TT> configuration files
and restart <TT>
<FONT COLOR="#0000ff">named</FONT></TT> without checking
<TT>
<FONT COLOR="#0000ff">/var/log/messages</FONT></TT> (or <TT>
<FONT COLOR="#0000ff">/var/log/syslog</FONT></TT>)
for errors. <I>NEVER</I> do this</I>.
<P>
<H2><A NAME="SECTION004323000000000000000">
40.2.3 Configuration in detail</A>
</H2>
<P>
If there are no apparent errors in your config files,
you can now more closely examine the contents of the files.
<P>
<H3><A NAME="SECTION004323100000000000000">
40.2.3.1 Top-level <TT>
<FONT COLOR="#0000ff">named.conf</FONT></TT></A>
</H3>
<P>
The top-level configuration file <TT>
<FONT COLOR="#0000ff">/etc/named.conf</FONT></TT>
has an obvious <B>C</B> style format. Comments are designated
by <TT>
<FONT COLOR="#0000ff">/* */</FONT></TT> or <TT>
<FONT COLOR="#0000ff">//</FONT></TT>.
<P>
The <TT>
<FONT COLOR="#0000ff">options</FONT></TT> section in our case specifies only one
parameter: the directory for locating any files. The file
<TT>
<FONT COLOR="#0000ff">options.html</FONT></TT> under the <TT>
<FONT COLOR="#0000ff">bind</FONT></TT> documentation directories
has a complete list of options. Some of these are esoteric,
but a few have common uses.
<P>
The lines <TT>
<FONT COLOR="#0000ff">zone "." {</FONT></TT>...<TT>
<FONT COLOR="#0000ff"> </FONT></TT>
will be present in all name server configurations. They tell
<TT>
<FONT COLOR="#0000ff">named</FONT></TT> that the whole Internet is governed by the
file <TT>
<FONT COLOR="#0000ff">named.ca</FONT></TT>. <TT>
<FONT COLOR="#0000ff">named.ca</FONT></TT> in turn contains the
list of root name servers.
<P>
The lines <TT>
<FONT COLOR="#0000ff">zone "localdomain" {</FONT></TT>...<TT>
<FONT COLOR="#0000ff"> </FONT></TT> are common.
They specify that forward lookups for <I>host</I><TT>
<FONT COLOR="#0000ff">.localdomain</FONT></TT>
are contained in the file <TT>
<FONT COLOR="#0000ff">/var/named/named.localdomain</FONT></TT>.
This file gives a correct result for any lookup for <TT>
<FONT COLOR="#0000ff">localhost</FONT></TT>.
Many applications query the name server for this name and
a fastidious configuration ought to return it correctly.
Note that such a lookup works together with <TT>
<FONT COLOR="#0000ff">resolv.conf</FONT></TT>--it
has a line <TT>
<FONT COLOR="#0000ff">search localdomain</FONT></TT> so that a query for
<TT>
<FONT COLOR="#0000ff">localhost</FONT></TT> gives the same result as a query for
<TT>
<FONT COLOR="#0000ff">localhost.localdomain</FONT></TT>.
<P>
The lines <TT>
<FONT COLOR="#0000ff">zone "1.0.0.127.in-addr.arpa" {</FONT></TT>...<TT>
<FONT COLOR="#0000ff"> </FONT></TT>
resolve reverse lookups for the IP address <TT>
<FONT COLOR="#0000ff">127.0.0.1</FONT></TT> (stored
in the file <TT>
<FONT COLOR="#0000ff">named.127.0.0.1</FONT></TT>). Note that <TT>
<FONT COLOR="#0000ff">1.0.0.127</FONT></TT> is
<TT>
<FONT COLOR="#0000ff">127.0.0.1</FONT></TT> written backwards. In fact, reverse lookups
are just forward lookups under the domain <TT>
<FONT COLOR="#0000ff">.in-addr.arpa</FONT></TT>.
Many applications reverse lookup any received connection to check
its authenticity, even from <TT>
<FONT COLOR="#0000ff">localhost</FONT></TT>, so you may want
to have these lines present to prevent such applications failing
or blocking.
<P>
The rest of the file is the configuration specific to our domain.
<P>
The lines <TT>
<FONT COLOR="#0000ff">zone "cranzgot.co.za" {</FONT></TT>...<TT>
<FONT COLOR="#0000ff"> </FONT></TT> say that information for
forward lookups is located in the file
<TT>
<FONT COLOR="#0000ff">named.cranzgot.co.za</FONT></TT>.
<P>
The lines <TT>
<FONT COLOR="#0000ff">zone "1.168.192.in-addr.arpa" {</FONT></TT>...<TT>
<FONT COLOR="#0000ff"> </FONT></TT> say that
information for reverse lookups on the IP address range
<TT>
<FONT COLOR="#0000ff">192.168.1.0</FONT></TT>-<TT>
<FONT COLOR="#0000ff">255</FONT></TT> is located in the file
<TT>
<FONT COLOR="#0000ff">named.192.168.1</FONT></TT>.
<P>
The lines <TT>
<FONT COLOR="#0000ff">zone "44.182.124.160.in-addr.arpa" {</FONT></TT>...<TT>
<FONT COLOR="#0000ff"> </FONT></TT> says that
information for reverse lookups on the IP address
<TT>
<FONT COLOR="#0000ff">160.124.182.44</FONT></TT> is located in the file
<TT>
<FONT COLOR="#0000ff">named.160.124.182.44</FONT></TT>.
<P>
<H3><A NAME="SECTION004323200000000000000">
40.2.3.2 Domain <TT>
<FONT COLOR="#0000ff">SOA</FONT></TT> records</A>
</H3>
<P>
Each of the other <TT>
<FONT COLOR="#0000ff">named.</FONT></TT> files has a similar format. They begin with
<TT>
<FONT COLOR="#0000ff">$TTL</FONT></TT> line and then an <TT>
<FONT COLOR="#0000ff">@ IN SOA</FONT></TT>. <TT>
<FONT COLOR="#0000ff">TTL</FONT></TT> stands for
<I>Time To Live</I>, the default expiration time for all subsequent entries.
This line not only prevents a <TT>
<FONT COLOR="#0000ff">No default TTL set</FONT></TT>... warning message,
but really tells the rest of the Internet how long to cache an entry. If
you plan on moving your site soon or often, set this to a smaller
value.
<TT>
<FONT COLOR="#0000ff">SOA</FONT></TT> stands for <I>Start of Authority</I>. The host name on the second
line specifies the authority for that domain, and the adjacent
<TT>
<FONT COLOR="#0000ff"><user>.<hostname></FONT></TT> specifies the email<A NAME="page:dnsemail"></A> address
of the responsible person.
<P>
The next few lines contain timeout specifications for cached
data and data propagation across the net. These are reasonable
defaults, but if you would like to tune these values, consult
the relevant documentation listed on page <A HREF="node43.html#page:binddocu"><IMG ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="crossref.png"></A>.
The values are all in seconds.
<P>
The <I>serial number</I> for the file (i.e., <TT>
<FONT COLOR="#0000ff">2000012101</FONT></TT>) is
used to tell when a change has been made and hence that new
data should be propagated to other servers. When updating the
file in any way, you must increment this serial number.
The format is conventionally <I>YYYYMMDDxx</I>--exactly ten digits.
<I>xx</I> begins with, say, <TT>
<FONT COLOR="#0000ff">01</FONT></TT> and is incremented with each change
made during a day.
<P>
<I>It is absolutely essential that the serial number be
updated whenever a file is edited. If not, the changes will not be
reflected through the rest of the Internet.</I>
<P>
<H3><A NAME="SECTION004323300000000000000">
40.2.3.3 Dotted and non-dotted host names</A>
</H3>
<P>
If a host name ends in a <TT>
<FONT COLOR="#0000ff">.</FONT></TT> then the dot signifies
a fully qualified host name. If it does not end in a <TT>
<FONT COLOR="#0000ff">.</FONT></TT>
then the absence of a dot signifies that the domain should be
appended to the host name. This feature is purely to make files
more elegant.
<P>
For instance, the line
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>ftp IN A 196.28.144.17</code><br>
</FONT></TD></TR></TABLE><P>
could just as well be written
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>ftp.cranzgot.co.za. IN A 196.28.144.17</code><br>
</FONT></TD></TR></TABLE><P>
<I>Always be careful to properly end qualified host names with a dot,
since failing to do so causes <TT>
<FONT COLOR="#0000ff">named</FONT></TT> to append a further
domain.</I>
<P>
<H3><A NAME="SECTION004323400000000000000">
40.2.3.4 Empty host names</A>
</H3>
<P>
If a host name is omitted from the start of the line, then the
domain is substituted. The purpose of this notation is also for
elegance. For example,
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code> IN NS ns1.cranzgot.co.za.</code><br>
</FONT></TD></TR></TABLE><P>
is the same as
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>cranzgot.co.za. IN NS ns1.cranzgot.co.za.</code><br>
</FONT></TD></TR></TABLE><P>
<P>
<H3><A NAME="SECTION004323500000000000000">
40.2.3.5 <TT>
<FONT COLOR="#0000ff">NS</FONT></TT>, <TT>
<FONT COLOR="#0000ff">MX</FONT></TT>, <TT>
<FONT COLOR="#0000ff">PTR</FONT></TT>, <TT>
<FONT COLOR="#0000ff">A</FONT></TT>, and <TT>
<FONT COLOR="#0000ff">CNAME</FONT></TT> records</A>
</H3>
<P>
Each DNS record appears on a single line, associating some
host name / domain or IP address with some other host name or IP
address.
Hence, it is easy to construct a file that makes the Internet
think anything you want it to about your organization.
<P>
The most basic types of record are the <TT>
<FONT COLOR="#0000ff">A</FONT></TT> and <TT>
<FONT COLOR="#0000ff">PTR</FONT></TT>
records. They simply associate a host name with an IP number,
or an IP number with a host name, respectively. You should not
have more than one host associated to a particular IP number.
<P>
The <TT>
<FONT COLOR="#0000ff">CNAME</FONT></TT> record says that a host is just an alias
to another host. So have
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>ns1 IN A 196.28.144.1</code><br>
<code>mail1 IN CNAME ns1.cranzgot.co.za.</code><br>
</FONT></TD></TR></TABLE><P>
rather than
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>ns1 IN A 196.28.144.1</code><br>
<code>mail1 IN A 196.28.144.1</code><br>
</FONT></TD></TR></TABLE><P>
<P>
Finally, <TT>
<FONT COLOR="#0000ff">NS</FONT></TT> and <TT>
<FONT COLOR="#0000ff">MX</FONT></TT> records
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code><domain> IN NS <nameserver></code><br>
<code><domain> IN MX <mailserver></code><br>
</FONT></TD></TR></TABLE><P>
just state that domain <TT>
<FONT COLOR="#0000ff"><domain></FONT></TT> has a name server or mail server
<TT>
<FONT COLOR="#0000ff"><nameserver></FONT></TT> or <TT>
<FONT COLOR="#0000ff"><mailserver></FONT></TT>, respectively. MTAs can now
locate your mail server as being responsible for email addresses of the
form <I>user</I><TT>
<FONT COLOR="#0000ff">@cranzgot.co.za</FONT></TT>.
<P>
<H3><A NAME="SECTION004323600000000000000">
40.2.3.6 Reverse lookups configuration</A>
</H3>
<P>
The file <TT>
<FONT COLOR="#0000ff">/var/named/named.196.28.144</FONT></TT> contains reverse
lookup data on all 255 IP addresses under <TT>
<FONT COLOR="#0000ff">196.28.144.</FONT></TT>.
It is, however, our ISP (called <TT>
<FONT COLOR="#0000ff">big-isp.net</FONT></TT>) that is responsible
for this address range, possibly having bought all 65536 addresses under
<TT>
<FONT COLOR="#0000ff">196.28.</FONT></TT>. The Internet is going to query <TT>
<FONT COLOR="#0000ff">big-isp.net</FONT></TT> when
trying to do a reverse lookup for <TT>
<FONT COLOR="#0000ff">196.28.144.</FONT></TT><I>?</I>.
The problem here is that there
are many companies comprising the <TT>
<FONT COLOR="#0000ff">196.28.144.</FONT></TT><I>?</I>
range, each with their own name server, so no single name server
can be authoritative for the whole domain <TT>
<FONT COLOR="#0000ff">144.28.196.in-addr.arpa</FONT></TT>.
This is the reason for lines in <TT>
<FONT COLOR="#0000ff">/var/named/named.196.28.144</FONT></TT> like
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>5 IN NS dns.big-isp.net.</code><br>
</FONT></TD></TR></TABLE><P>
IP address <TT>
<FONT COLOR="#0000ff">196.28.144.5</FONT></TT>
is not our responsibility, and hence we refer any such query to a more
authoritative name server. On the ISP side, the name server <TT>
<FONT COLOR="#0000ff">dns.big-isp.net</FONT></TT>
must have a file <TT>
<FONT COLOR="#0000ff">/var/named/named.196.28.144</FONT></TT> that contains something
like:
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red size="-1">
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>5</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>10</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>15</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>20</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>25</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>30</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>35</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>40</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-2"><code>45</code></font><code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue size="-1">
<code>$TTL 259200</code><br>
<code>@ IN SOA dns.dns.big-isp.net. dns-admin.dns.big-isp.net. (</code><br>
<code> 2000012101 ; Serial number</code><br>
<code> 10800 ; Refresh every 3 hours</code><br>
<code> 3600 ; Retry every hour</code><br>
<code> 3600000 ; Expire after 42 days</code><br>
<code> 259200 ) ; Minimum Time to Live (TTL) of 3 days</code><br>
<code> </code><br>
<code> IN NS dns.big-isp.net.</code><br>
<code> </code><br>
<code>0 IN NS ns1.dali.co.za.</code><br>
<code>1 IN NS ns1.dali.co.za.</code><br>
<code>2 IN NS ns1.dali.co.za.</code><br>
<code>3 IN NS ns1.dali.co.za.</code><br>
<code>4 IN NS ns1.dali.co.za.</code><br>
<code>5 IN NS ns1.dali.co.za.</code><br>
<code>6 IN NS ns1.dali.co.za.</code><br>
<code>7 IN NS ns1.dali.co.za.</code><br>
<code> </code><br>
<code>8 IN NS ns1.picasso.co.za.</code><br>
<code>9 IN NS ns1.picasso.co.za.</code><br>
<code>10 IN NS ns1.picasso.co.za.</code><br>
<code>11 IN NS ns1.picasso.co.za.</code><br>
<code>12 IN NS ns1.picasso.co.za.</code><br>
<code>13 IN NS ns1.picasso.co.za.</code><br>
<code>14 IN NS ns1.picasso.co.za.</code><br>
<code>15 IN NS ns1.picasso.co.za.</code><br>
<code> </code><br>
<code>16 IN NS ns1.cranzgot.co.za.</code><br>
<code>17 IN NS ns1.cranzgot.co.za.</code><br>
<code>18 IN NS ns1.cranzgot.co.za.</code><br>
<code>19 IN NS ns1.cranzgot.co.za.</code><br>
<code>20 IN NS ns1.cranzgot.co.za.</code><br>
<code>21 IN NS ns1.cranzgot.co.za.</code><br>
<code>22 IN NS ns1.cranzgot.co.za.</code><br>
<code>23 IN NS ns1.cranzgot.co.za.</code><br>
<code> </code><br>
<code>24 IN NS ns1.matisse.co.za.</code><br>
<code>25 IN NS ns1.matisse.co.za.</code><br>
<code>26 IN NS ns1.matisse.co.za.</code><br>
<code>27 IN NS ns1.matisse.co.za.</code><br>
<code>28 IN NS ns1.matisse.co.za.</code><br>
<code>29 IN NS ns1.matisse.co.za.</code><br>
<code>30 IN NS ns1.matisse.co.za.</code><br>
<code>31 IN NS ns1.matisse.co.za.</code><br>
<code>; and so on... up to 255</code><br>
</FONT></TD></TR></TABLE><P>
<P>
Here, Matisse, Dali, and Picasso are other companies that have
bought small IP address blocks from <TT>
<FONT COLOR="#0000ff">big-isp</FONT></TT>. Each of
these lines will redirect queries to the appropriate name server.
<P>
<H1><A NAME="SECTION004330000000000000000">
40.3 Round-Robin Load-Sharing</A>
</H1>
<P>
<A NAME="sec:roundrobdns"></A>
If you have more than one <TT>
<FONT COLOR="#0000ff">A</FONT></TT> record for a particular machine,
then <TT>
<FONT COLOR="#0000ff">named</FONT></TT> will return multiple IP addresses upon a lookup.
Load sharing between several web servers is now possible--the
record ordering is randomized with each new lookup and your
web browser will only choose the first listed IP address.
For instance, <TT>
<FONT COLOR="#0000ff">host cnn.com</FONT></TT> returns several IP addresses.
Their zone file configuration might look like
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-1"><code>5</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>cnn.com. IN A 207.25.71.5</code><br>
<code>cnn.com. IN A 207.25.71.6</code><br>
<code><font color="navy"><B>.</B></font></code><br>
<code><font color="navy"><B>.</B></font></code><br>
<code><font color="navy"><B>.</B></font></code><br>
<code>cnn.com. IN A 207.25.71.29</code><br>
<code>cnn.com. IN A 207.25.71.30</code><br>
</FONT></TD></TR></TABLE><P>
<P>
<H1><A NAME="SECTION004340000000000000000">
40.4 Configuring <TT>
<FONT COLOR="#0000ff">named</FONT></TT> for Dialup Use</A>
</H1>
<P>
If you have a dialup connection, the name server should be
configured as what is called a <I>caching-only</I> name server.
Of course, there is no such thing as a caching-<I>only</I>
name server--the term just means that the <TT>
<FONT COLOR="#0000ff">name.</FONT></TT> files have
only a few essential records in them. The point of a caching
server is to prevent spurious DNS lookups that may eat modem
bandwidth or cause a dial-on-demand server to initiate a
dialout. It also prevents applications blocking, waiting for a
DNS lookup. (Typical examples are <TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT>, which
blocks for a couple of minutes when a machine is turned on
without the network plugged in; and
<TT>
<FONT COLOR="#0000ff">netscape</FONT></TT> 4, which tries to look up the IP address of
<TT>
<FONT COLOR="#0000ff">news.<localdomain></FONT></TT>.)
<P>
<H2><A NAME="SECTION004341000000000000000">
40.4.1 Example caching name server</A>
</H2>
<P>
For a caching name server, the <TT>
<FONT COLOR="#0000ff">/etc/name.conf</FONT></TT> file
should look as follows. Replace
<TT>
<FONT COLOR="#0000ff"><nameserver></FONT></TT> with the IP address of the name server
your ISP has given you. Your local machine name is assumed to
be <TT>
<FONT COLOR="#0000ff">cericon.priv.ate</FONT></TT>. (The following listings are minus
superfluous comments and newlines for brevity):
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-1"><code>5</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-1"><code>10</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>options {</code><br>
<code> forwarders {</code><br>
<code> <nameserver>;</code><br>
<code> };</code><br>
<code> directory "/var/named";</code><br>
<code>};</code><br>
<code> </code><br>
<code>zone "." { type hint; file "named.ca"; };</code><br>
<code>zone "localdomain" { type master; file "named.localdomain"; };</code><br>
<code>zone "1.0.0.127.in-addr.arpa" { type master; file "named.127.0.0.1";};</code><br>
<code>zone "priv.ate" { type master; file "named.priv.ate"; };</code><br>
<code>zone "168.192.in-addr.arpa" { type master; file "named.192.168"; };</code><br>
</FONT></TD></TR></TABLE><P>
<P>
The <TT>
<FONT COLOR="#0000ff">/var/named/named.priv.ate</FONT></TT> file should look like:
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-1"><code>5</code></font><code> </code><br>
<code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>$TTL 259200</code><br>
<code>@ IN SOA cericon.priv.ate. root.cericon.priv.ate. </code><br>
<code> ( 2000012101 10800 3600 3600000 259200 )</code><br>
<code> IN NS cericon.priv.ate.</code><br>
<code>cericon IN A 192.168.1.1</code><br>
<code>news IN A 192.168.1.2</code><br>
</FONT></TD></TR></TABLE><P>
<P>
The <TT>
<FONT COLOR="#0000ff">/var/named/named.192.168</FONT></TT> file should look like:
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-1"><code>5</code></font><code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>$TTL 259200</code><br>
<code>@ IN SOA localhost. root.localhost.</code><br>
<code> ( 2000012101 10800 3600 3600000 259200 )</code><br>
<code> IN NS localhost.</code><br>
<code>1.1 IN PTR cericon.priv.ate.</code><br>
</FONT></TD></TR></TABLE><P>
<P>
The remaining files are the same as before.
In addition to the above, your host name has
to be configured as in Chapter <A HREF="node30.html#chap:dns">27</A>.
<P>
<H2><A NAME="SECTION004342000000000000000">
40.4.2 Dynamic IP addresses</A>
</H2>
<P>
The one contingency of dialup machines is that IP addresses are
often dynamically assigned, so your <TT>
<FONT COLOR="#0000ff">192.168.</FONT></TT> addresses
aren't going to apply. Probably one way to get around this is to
dial in a few times to get a feel for what IP addresses you are
likely to get. Assuming you know that your ISP always gives you
<TT>
<FONT COLOR="#0000ff">196.26.</FONT></TT><I>x</I><TT>
<FONT COLOR="#0000ff">.</FONT></TT><I>x</I>, you can have a reverse
lookup file <TT>
<FONT COLOR="#0000ff">named.196.26</FONT></TT> with nothing in it. This will
just cause reverse lookups to fail instead of blocking.
<P>
Such a ``hack'' is probably unnecessary. It is best to
identify the particular application that is causing a spurious
dialout or causing a block, and then apply your creativity to the
particular case.
<P>
<H1><A NAME="SECTION004350000000000000000">
40.5 Secondary or Slave DNS Servers</A>
</H1>
<P>
<TT>
<FONT COLOR="#0000ff">named</FONT></TT> can operate as a backup server to another
server, also called a <I>slave</I> or <I>secondary</I> server.
<P>
Like the caching-<I>only</I> server there, is no such thing
as a <I>secondary</I> server. It's just the same <TT>
<FONT COLOR="#0000ff">named</FONT></TT>
running with reduced capacity.
<P>
Let's say we would like <TT>
<FONT COLOR="#0000ff">ns2.cranzgot.co.za</FONT></TT> to be a secondary
to <TT>
<FONT COLOR="#0000ff">ns1.cranzgot.co.za</FONT></TT>. The <TT>
<FONT COLOR="#0000ff">named.conf</FONT></TT> file would
look as follows:
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-1"><code>5</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-1"><code>10</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-1"><code>15</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-1"><code>20</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-1"><code>25</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-1"><code>30</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-1"><code>35</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-1"><code>40</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-1"><code>45</code></font><code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<code> </code><br>
<font size="-1"><code>50</code></font><code> </code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>options {</code><br>
<code> directory "/var/named";</code><br>
<code>};</code><br>
<code> </code><br>
<code>zone "." {</code><br>
<code> type hint;</code><br>
<code> file "named.ca";</code><br>
<code>};</code><br>
<code> </code><br>
<code>zone "localdomain" {</code><br>
<code> type master;</code><br>
<code> file "named.localdomain";</code><br>
<code>};</code><br>
<code> </code><br>
<code>zone "1.0.0.127.in-addr.arpa" {</code><br>
<code> type master;</code><br>
<code> file "named.127.0.0.1";</code><br>
<code>};</code><br>
<code> </code><br>
<code>zone "cranzgot.co.za" {</code><br>
<code> type slave;</code><br>
<code> file "named.cranzgot.co.za";</code><br>
<code> masters {</code><br>
<code> 196.28.144.16;</code><br>
<code> };</code><br>
<code>};</code><br>
<code> </code><br>
<code>zone "2.168.192.in-addr.arpa" {</code><br>
<code> type slave;</code><br>
<code> file "named.192.168.2";</code><br>
<code> masters {</code><br>
<code> 196.28.144.16;</code><br>
<code> };</code><br>
<code>};</code><br>
<code> </code><br>
<code>zone "144.28.196.in-addr.arpa" {</code><br>
<code> type slave;</code><br>
<code> file "named.196.28.144";</code><br>
<code> masters {</code><br>
<code> 196.28.144.16;</code><br>
<code> };</code><br>
<code>};</code><br>
<code> </code><br>
<code>zone "44.181.123.160.in-addr.arpa" {</code><br>
<code> type slave;</code><br>
<code> file "named.160.123.181.44";</code><br>
<code> masters {</code><br>
<code> 196.28.144.16;</code><br>
<code> };</code><br>
<code>};</code><br>
</FONT></TD></TR></TABLE><P>
<P>
When an entry has a ``<TT>
<FONT COLOR="#0000ff">master</FONT></TT>'' in it, you must supply
the appropriate file.
When an entry has a ``<TT>
<FONT COLOR="#0000ff">slave</FONT></TT>'' in it, <TT>
<FONT COLOR="#0000ff">named</FONT></TT> will
automatically download the file from <TT>
<FONT COLOR="#0000ff">196.28.144.16</FONT></TT> (i.e.,
<TT>
<FONT COLOR="#0000ff">ns1.cranzgot.co.za</FONT></TT>) the first time a lookup is required
from that domain.
<P>
<I>And that's DNS!</I>
<P>
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