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Q297795: HOW TO: Enable Reverse DNS Lookup for IIS

Article: Q297795
Product(s): Internet Information Server
Version(s): 4.0,5.0
Operating System(s): 
Keyword(s): kbHOWTOmaster
Last Modified: 12-JUL-2002

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The information in this article applies to:

- Microsoft Internet Information Server version 4.0 
- Microsoft Internet Information Services version 5.0 
- Microsoft Internet Information Services version 5.1 
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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 "Configuration Backup/Restore" Help topic in Microsoft Management Console (MMC).

IN THIS TASK
------------

- SUMMARY

   - Enable Reverse DNS Lookup
- IIS 4.0
- IIS 5.0 and 5.1
- Warnings

- REFERENCES

SUMMARY
=======

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

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 4.0 (which is included with Microsoft Windows
NT 4.0), IIS 5.0 (which is included with Microsoft Windows 2000), and IIS 5.1
(which is included with Microsoft Windows XP Professional), 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.

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

  Q300672 HOW TO: Create a Metabase Backup in IIS 5

IIS 4.0
-------

1. Open a command prompt.

2. Change the folder to %systemroot%\Inetsrv\Adminsamples.

3. Type "adsutil set w3svc/EnableReverseDNS TRUE" (without the quotation marks),
  and then press ENTER.

IIS 5.0 and IIS 5.1
-------------------

1. Open a command prompt.

2. Change the folder to C:\Inetpub\Adminscripts.

3. Type "adsutil set w3svc/EnableReverseDNS TRUE" (without the quotation marks),
  and then press ENTER.

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.

REFERENCES
==========

For additional information about performing reverse DNS lookup, click the
article numbers below to view the articles in the Microsoft Knowledge Base:

  Q245574 HOWTO: Configure REMOTE_HOST to Perform a Reverse DNS Lookup in IIS

  Q227943 How Internet Information Services (IIS) Handles Reverse Lookup
  Failures

For additional information about restricting site access by IP address or domain
name, click the article number below to view the article in the Microsoft
Knowledge Base:

  Q324066 HOW TO: Restrict Site Access by IP Address or Domain Name

Additional query words:

======================================================================
Keywords          : kbHOWTOmaster 
Technology        : kbiisSearch kbiis500 kbiis400 kbiis510
Version           : :4.0,5.0
Issue type        : kbhowto

=============================================================================

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