Windows NT 4.0 SP4 DNR Client Does Not Send Unqualified DNS Queries

ID: Q230744

The information in this article applies to:
IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to do this, view the "Restoring the Registry" Help topic in Regedit.exe or the "Restoring a Registry Key" Help topic in Regedt32.exe.

SYMPTOMS

The Domain Name Resolver (DNR) client implemented in Windows NT 4.0 Service Pack 4 (SP4) does not send unqualified queries to the Domain Name System (DNS) server.


CAUSE

An unqualified query is a DNS short name query for the host name sent after stripping the domain name portion of the Fully Qualified Domain Name (FQDN). This is not a valid DNS query. Eliminating this last short name query from the DNS lookup phase in SP4 enhances DNR performance.


RESOLUTION

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys and Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT, you should also update your Emergency Repair Disk (ERD).

If you want to re-enable last short name query using DNS, set the data value of the AllowUnqualifiedQuery value to 1 in the following registry key:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters\

Value Name: AllowUnqualifiedQuery
Data Type: REG_DWORD
Valid Range: 0-1
Default: 0


MORE INFORMATION

"Devolution" may be appropriate in normal DNR usage. If a DNS query for client.domainname.com is unresolved, it is devolved to client.com and eventually to client. This last unqualified query is eliminated from the name query process.


REFERENCES

For additional information about DNR optimization and name devolution enhancements in SP4, please see the following articles in the Microsoft Knowledge Base:

Q198550 SP4 Changes DNS Name Resolution
Q195611 DNS Client Does Not Try All Servers in DNS Service List
Q214467 Windows NT 4.0 DNR Only "Devolves" Two Domain Suffixes

Additional query words: 


Keywords          : kbenv kbnetwork ntsp kbbug4.00 kbfix4.00 
Version           : winnt:4.0 SP4
Platform          : winnt 
Issue type        : kbprb

Last Reviewed: July 2, 1999