Microsoft KB Archive/297795

= HOW TO: Enable Reverse DNS Lookup for IIS =

Article ID: 297795

Article Last Modified on 12/3/2007

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APPLIES TO


 * Microsoft Internet Information Server 4.0
 * Microsoft Internet Information Services 5.0
 * Microsoft Internet Information Services 5.1
 * Microsoft Internet Information Services 6.0

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This article was previously published under Q297795



We strongly recommend that all users upgrade to Microsoft Internet Information Services (IIS) version 6.0 running on Microsoft Windows Server 2003. IIS 6.0 significantly increases Web infrastructure security. For more information about IIS security-related topics, visit the following Microsoft Web site:

http://www.microsoft.com/technet/security/prodtech/IIS.mspx



IMPORTANT: This article contains information about editing the metabase. Before you edit the metabase, verify that you have a backup copy that you can restore if a problem occurs. For information about how to do this, see the &quot;Configuration Backup/Restore&quot; Help topic in Microsoft Management Console (MMC).

IN THIS TASK

 * SUMMARY
 * Enable Reverse DNS Lookup
 * IIS 4.0
 * IIS 5.0 and Later
 * Warnings
 * REFERENCES



SUMMARY
This step-by-step article demonstrates how to enable reverse Domain Name System (DNS) lookup for Internet Information Services (IIS).

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Enable Reverse DNS Lookup
WARNING: If you edit the metabase incorrectly, you can cause serious problems that may require you to reinstall any product that uses the metabase. Microsoft cannot guarantee that problems that result if you incorrectly edit the metabase can be solved. Edit the metabase at your own risk.

NOTE: Always back up the metabase before you edit it.

To enable reverse DNS lookup on IIS versions 4.0 and later, the EnableReverseDNS metabase entry must be set to TRUE.

When the EnableReverseDNS metabase entry is set to TRUE, the IP address of each Web client that connects to the IIS server is resolved to a DNS name, and the DNS name instead of the Web client IP address is placed in the IIS log files. Enabling reverse DNS also affects what CGI and ISAPI extensions see as a value of the RemoteHost variable.

For additional information about how to back up the registry, click the article number below to view the article in the Microsoft Knowledge Base:

300672 HOW TO: Create a Metabase Backup in IIS 5

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IIS 4.0

 * 1) Open a command prompt.
 * 2) Change the folder to %systemroot%\Inetsrv\Adminsamples.
 * 3) Type adsutil set w3svc/EnableReverseDNS TRUE, and then press ENTER.

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IIS 5.0 and Later

 * 1) Open a command prompt.
 * 2) Change the folder to C:\Inetpub\Adminscripts.
 * 3) Type adsutil set w3svc/EnableReverseDNS TRUE, and then press ENTER.

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Warnings
Enabling reverse DNS on your IIS server can affect the performance of your Web server and DNS servers. Some examples are:
 * Resources such as CPU utilization and network bandwidth may be taken up.
 * Client requests can take longer to process.
 * Client requests can be blocked if IP restrictions by DNS domain names are used.

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