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Q217136: DNS Converts Host Names to Lowercase

Article: Q217136
Product(s): Microsoft Windows NT
Version(s): winnt:4.0
Operating System(s): 
Keyword(s): kbWinNT400sp5fix
Last Modified: 11-JUN-2002

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The information in this article applies to:

- Microsoft Windows NT Server version 4.0 
- Microsoft Windows NT Workstation version 4.0 
- Microsoft Windows NT Server, Enterprise Edition version 4.0 
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IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

  Q256986 Description of the Microsoft Windows Registry

SYMPTOMS
========

After you apply Windows NT Service Pack 4 to the Windows NT DNS server, clients
that try to access a UNIX computer receive the following error message:

  Access Denied

RESOLUTION
==========

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or
the individual software update. For information on obtaining the latest service
pack, please go to:

- http://www.microsoft.com/Windows/ServicePacks/

-or-

- Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack

For information on obtaining the individual software update, contact Microsoft
Product Support Services. For a complete list of Microsoft Product Support
Services phone numbers and information on support costs, please go to the
following address on the World Wide Web:

  http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS


STATUS
======

Microsoft has confirmed this to be a problem in Windows NT 4.0. This problem was
first corrected in Windows NT version 4.0 Service Pack 5.

MORE INFORMATION
================

The UNIX computer can use Reverse Lookup against the Windows NT DNS server to
identify and validate its clients. For additional information about Reverse
Lookup, please see the following article(s) in the Microsoft Knowledge Base:

  Q164213 Description of DNS Reverse Lookups

Windows NT SP3 Dns.exe maintained mixed case host names. The list of names on the
UNIX machine that is used to validate clients against was held using mixed case
names also. Doing a Reverse Lookup, the names returned from the DNS server
matched the names on the UNIX side and the clients were granted access.

Windows NT SP4 Dns.exe, however, converts all names to lowercase. As lowercase
names are returned upon Reverse Lookup requests, the names returned do not match
the names on the UNIX side and, therefore, "access denied" is returned.

To resolve this problem, a new Dns.exe now has a registry entry that makes
uppercase and lowercase handling configurable.

WARNING: If you use Registry Editor incorrectly, you may cause serious problems
that may require you to reinstall your operating system. Microsoft cannot
guarantee that you can solve problems that result from using Registry Editor
incorrectly. Use Registry Editor at your own risk.

  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DNS\Parameters
  CasePreservation (REG_DWORD)

Setting this to 1 will turn on case preservation.

This has been resolved because of compatibility reasons. Please note, however,
that RFC 952 describes that there should be no code and functionality depending
on uppercase or lowercase of a DNS response. Therefore, maintaining a mixed case
host list is not according RFC.


Additional query words: 4.00

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Keywords          : kbWinNT400sp5fix 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400 kbWinNTS400search kbWinNTS400
Version           : winnt:4.0
Hardware          : ALPHA x86
Issue type        : kbbug
Solution Type     : kbfix

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