104 lines
6.6 KiB
HTML
104 lines
6.6 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Problem: DNS records are not being updated by DHCP" />
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<meta name="abstract" content="The iSeries DHCP server is capable of dynamically updating DNS resource records. Dynamic update errors might be caused by the failure of DNS records update." />
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<meta name="description" content="The iSeries DHCP server is capable of dynamically updating DNS resource records. Dynamic update errors might be caused by the failure of DNS records update." />
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<meta name="DC.Relation" scheme="URI" content="rzakgtroubleshooting.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzakgconceptddns.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2004, 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 2004, 2006" />
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<meta name="DC.Identifier" content="rzakgproblemddns" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Problem: DNS records are not being updated by DHCP</title>
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</head>
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<body id="rzakgproblemddns"><a name="rzakgproblemddns"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Problem: DNS records are not being updated by DHCP</h1>
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<div><p>The iSeries™ DHCP
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server is capable of dynamically updating DNS resource records. Dynamic update
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errors might be caused by the failure of DNS records update.</p>
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<p>Refer to <a href="rzakgconceptddns.htm#rzakgconceptddns">Dynamic updates</a> for
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details about this capability. The DHCP server uses name resolution functions
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and programming interfaces to determine the appropriate dynamic DNS server
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to update. You can use this to your advantage when determining the source
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of dynamic update errors.</p>
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<p>Check the following points when the DNS records are not
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being updated dynamically.</p>
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<dl><dt class="dlterm">Verify which subnets and the type of resource records (A and/or PTR records)
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are being updated.</dt>
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<dd> Check the DHCP configuration and verify that the client's subnet is set
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up to dynamically update resource records and which type of record is being
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updated.</dd>
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</dl>
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<dl><dt class="dlterm">Verify that i5/OS™ Option 31 (Domain Name System) is
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installed on the iSeries server
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that is running DHCP.</dt>
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<dd>The DHCP server uses programming interfaces provided by i5/OS Option
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31. The DNS that is being dynamically updated does not need to reside on the
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same iSeries server
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as the DHCP server.</dd>
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</dl>
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<dl><dt class="dlterm">Verify the DHCP server is authorized to send updates to the DNS server.</dt>
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<dd>Check the DNS configuration to verify the DNS zone is configured to allow
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dynamic updates and that the DHCP server is included in the Access Control
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List.</dd>
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</dl>
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<dl><dt class="dlterm">Verify that the DNS servers can resolve the client's domain.</dt>
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<dd>Display the list of DNS servers on the iSeries server where DHCP resides using
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the CHGTCPDMN command. Verify that these DNS servers can resolve the domain
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that is being updated. To do this, run NSLOOKUP from the iSeries server
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where DHCP is running to resolve a name (or IP address) that exists in the
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domain that is failing to be updated. The DHCP server must be able to derive
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the fully qualified domain name (FQDN) of the client to update its DNS record.
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The DHCP server will not attempt to update a dynamic DNS without a FQDN (the
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host name and domain name of the client). The DHCP server derives the FQDN
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of the client using the following sequence:<ol><li>Option 81 (Client FQDN) in the DHCPREQUEST message from the client.</li>
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<li>Option 12 (Host Name) and/or Option 15 (Domain Name) in the DHCPREQUEST
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message from the client.</li>
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<li>Option 12 (Host Name) in the DHCPREQUEST message from the client and/or
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Option 15 (Domain Name) configured in the DHCP server. In this case, to derive
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the FQDN, the DHCP server must be configured to append the domain name to
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the host name (specified on the <span class="menucascade"><span class="uicontrol">Properties</span> > <span class="uicontrol">Dynamic DNS</span></span> tab for the global level,
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subnet, class, or client).</li>
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</ol>
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</dd>
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</dl>
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<dl><dt class="dlterm">The TXT record might not match the corresponding DNS record.</dt>
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<dd>The DHCP server can be configured to check the existing DNS resource records
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to determine which DHCP client they are associated with. The DHCP server accomplishes
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this by writing a corresponding TXT record with each A and PTR record that
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it updates in the DNS. If the server is configured to verify the client ID
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before performing the DNS update, then the TXT record data must match the
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client ID of the client that received the address from the DHCP server. If
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it does not match, the DHCP server will not update the DNS A resource record.
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This is done to prevent overwriting existing records. However, the DHCP server
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can be configured to ignore the existing records and perform DNS updates regardless
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of the data in the TXT record (specified on the <span class="menucascade"><span class="uicontrol">Properties</span> > <span class="uicontrol">Dynamic DNS</span></span> tab for the global level,
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subnet, class, or client).</dd>
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</dl>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzakgtroubleshooting.htm" title="You can view job log and trace data, as well as use troubleshooting lists for common problems.">Troubleshoot DHCP</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="rzakgconceptddns.htm" title="You can use your DHCP server in conjunction with your DNS server to dynamically update the client information in the DNS when DHCP assigns the client an IP address.">Dynamic updates</a></div>
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</div>
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</div>
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</body>
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</html>
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