Microsoft KB Archive/929587

= Host (A) records may contain incorrect IP addresses if you configure a Windows Server 2003-based DHCP server to update A records and PTR records in DNS =

Article ID: 929587

Article Last Modified on 10/29/2007

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APPLIES TO


 * Microsoft Windows Server 2003, Standard Edition (32-bit x86)
 * Microsoft Windows Server 2003, Enterprise Edition
 * Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)

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SYMPTOMS
On a Dynamic Host Configuration Protocol (DHCP) server that is running Microsoft Windows Server 2003, the host (A) records for one or more clients may include incorrect IP addresses. Therefore, Domain Name System (DNS) cannot resolve the names of these clients to correct IP addresses.

This problem occurs if you configure the server to update A records and pointer (PTR) records in DNS.



CAUSE
This problem occurs when either of the following conditions is true:
 * There is no reverse lookup zone for the IP subnet.
 * The reverse lookup zone is not configured to allow for dynamic updates.

If you configure a client computer to use dynamic IP configuration, the client computer requests an IP address from the DHCP server when the client computer starts. The DHCP server provides an IP lease to the client computer. Then, the DHCP server tries to register an A record and a PTR record in DNS. However, the registration for the PTR record may fail when a reverse lookup zone that allows for dynamic updates is not present. In this situation, the DHCP server tries to reregister the A record and the PTR record after the DHCP database cleanup interval expires. In Windows Server 2003, the default setting for the DHCP database cleanup interval is 60 minutes. If one of the client computers has moved to a new subnet, the new IP address is registered in DNS. Then, when the DHCP database cleanup occurs, the DHCP server tries to perform the registration that previously failed. In this case, the DHCP server registers the A record by using the old IP address. The A record that contains the old IP address overwrites the correct A record.



RESOLUTION
To resolve this problem, create a reverse lookup zone for the subnet that hosts the client computer in DNS. Then, configure the reverse lookup zone to allow for dynamic updates.

For more information about how to add a reverse lookup zone, visit the following Microsoft Web site:

http://technet2.microsoft.com/windowsserver/en/library/c12222ef-8350-48bc-8b48-25f78681d2a01033.mspx



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
To configure the server to update A records and PTR records in DNS, use one or both of the following settings in the Scope Properties dialog box:
 * Dynamically update DNS A and PTR records for DHCP clients that do not request updates (for example, clients running Windows NT 4.0)
 * Always dynamically update DNS A and PTR records

For more information about DHCP database cleanup interval, visit the following Microsoft Web site:

http://technet2.microsoft.com/WindowsServer/en/library/df9ecef3-7d85-49e6-a2aa-ff84a5bd3a391033.mspx?mfr=true

Keywords: kbexpertiseinter kbtshoot kbprb KB929587

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