Windows NT 4.0 Domain Name Resolver Caches Responses Regardless of Registry Setting

ID: Q187709

The information in this article applies to:

SYMPTOMS

When a Windows Sockets application uses DNS to resolve a hostname to an IP address by means of the gethostbyname API, the Domain Name Resolver (DNR) on a computer running Windows NT 4.0 caches the response for the TTL (Time to Live) specified in the response on a per-process basis. This means that if there is a change in the IP address of the host computer, the client application continues to try connecting to the old address. It also means that the same IP address will be used each time, until the TTL expires, if the response contains multiple IP addresses.


CAUSE

Winsock2 support was introduced in Windows NT 4.0. Previous versions of Windows NT supported a MaxHostentCacheSize registry value, which you could set to zero to disable caching. Support for this parameter was not included in Winsock2.


RESOLUTION

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, please see the following article in the Microsoft Knowledge Base:

Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack

Support for the MaxHostentCacheSize registry value has been added to Winsock2. The registry value controls the number of cache entries that are available to the process. If you set the value to zero, no caching will be done.

HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\ServiceProvider
\MaxHostentCacheSize

NOTE: The above link is one path; it has been wrapped for readability.

Value type: REG_DWORD
Default value: 10


STATUS

Microsoft has confirmed this to be a problem in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition. This problem was first corrected in Windows NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.


Keywords          : NT4SP4Fix kbbug4.00 kbfix4.00.sp4 
Version           : WinNT:4.0
Platform          : winnt 
Issue type        : kbbug

Last Reviewed: April 10, 1999