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<h1 class="topictitle1">Example: Single Domain Name System server for an intranet</h1>
<div><p>This example depicts a simple subnet with a Domain Name System
(DNS) server for internal use.</p>
<div class="section"><p>The following illustration depicts DNS running on an iSeries™ for
an internal network. This single DNS server instance is set up to listen for
queries on all interface IP addresses. The server is a primary name server
for the mycompany.com zone.</p>
<div class="fignone"><span class="figcap">Figure 1. Single DNS server for an intranet</span><br /><img src="rzakk500.gif" alt="Single DNS server for an intranet." /><br /></div>
<p>Each host in the zone has an IP address and a domain name. The administrator
must manually define the hosts in the DNS zone data by creating resource records.
Address mapping (A) records map the name of a machine to its associated IP
address. This allows other hosts on the network to query the DNS server to
find the IP address assigned to a particular host name. Reverse-lookup pointer
(PTR) records map the IP address of a machine to its associated name. This
allows other hosts on the network to query the DNS server to find the host
name that corresponds to an IP address.</p>
<p>In addition to A and PTR records,
DNS supports many other resource records that might be required, depending
on what other TCP/IP based applications that you are running on your intranet.
For example, if you are running internal e-mail systems, you might need to
add mail exchanger (MX) records so that SMTP can query DNS to find out which
systems are running the mail servers.</p>
<p>If this small network were part
of a larger intranet, it might be necessary to define internal root servers.</p>
</div>
<div class="section"><h4 class="sectiontitle">Secondary servers</h4><p>Secondary servers load zone data
from the authoritative server. Secondary servers obtain zone data by doing
zone transfers from the authoritative server. When a secondary name server
starts, it requests all data for the specified domain from the primary name
server. A secondary name server requests updated data from the primary server
either because it receives notification from the primary name server (if the
NOTIFY function is being used) or because it queries the primary name server
and determines that the data has changed. In the figure 2, the myiseries server
is part of an intranet. Another iSeries server, myiseries2, has been
configured to act as a secondary DNS server for the mycompany.com zone. The
secondary server can be used to balance the demand on servers and also to
provide a backup in case the primary server goes down. It is a good practice
to have at least one secondary server for every zone.</p>
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<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="rzakkexampleparent.htm" title="You can use these examples to understand how to use Domain Name System (DNS) in your network.">Domain Name System examples</a></div>
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<div class="relref"><strong>Related reference</strong><br />
<div><a href="rzakkconceptresourcerec.htm" title="This topic explains how resource records are used by Domain Name System (DNS). Resource records are used to store data about domain names and IP addresses. This topic contains a searchable list of resource records supported for OS/400 V5R1.">Domain Name System resource records</a></div>
<div><a href="rzakkconceptbasic.htm" title="This topic explains Domain Name System (DNS) zones and zone types.">Understanding zones</a></div>
<div><a href="rzakkscenario2.htm" title="This example depicts a simple subnet with a Domain Name System (DNS) server connected directly to the Internet.">Example: Single Domain Name System server with Internet access</a></div>
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