DOCUMENT:Q187709 09-AUG-2001 [winnt] TITLE :Domain Name Resolver Caches Responses PRODUCT :Microsoft Windows NT PROD/VER:WinNT:4.0 OPER/SYS: KEYWORDS:kbWinNT400sp4fix ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Workstation version 4.0 - Microsoft Windows NT Server version 4.0 - Microsoft Windows NT Server version 4.0, Terminal Server Edition ------------------------------------------------------------------------------- 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 : kbWinNT400sp4fix Technology : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400 kbNTTermServ400 kbNTTermServSearch Version : WinNT:4.0 Hardware : ALPHA x86 Issue type : kbbug Solution Type : kbfix ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2001.