DOCUMENT:Q221926 11-JUN-2002 [winnt] TITLE :TCP/IP Forwarding Buffer Grows to Use Available Kernel Memory PRODUCT :Microsoft Windows NT PROD/VER:winnt:4.0 SP4 OPER/SYS: KEYWORDS: ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Server version 4.0 SP4 - Microsoft Windows NT Workstation version 4.0 SP4 - Microsoft Windows NT Server, Enterprise Edition version 4.0 SP4 ------------------------------------------------------------------------------- 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 ======== The forward buffer used with TCP/IP to buffer routed packets between interfaces can grow to use all available kernel memory in Windows NT computers running Windows NT 4.0 Service Pack 4. Or, you may see the following event information in the System log in Event Viewer: Event ID: 2019 Description: The server was unable to allocate from the system nonpaged pool because the pool was empty. CAUSE ===== The default maximum forwarding buffer size is 0xFFFFFFF bytes. Therefore, the buffer can grow to use all available system resources in this configuration. RESOLUTION ========== 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. To work around this problem, add the following registry entries to the server running Windows NT 4.0 and modify the values to disallow memory usage to degrade system performance: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters - MaxForwardBufferMemory (REG_DWORD: 74240) Establishes the maximum number of bytes of memory that the IP can allocate to store packet data in the router packet queue. This value must be greater than or equal to the value of ForwardBufferMemory. This registry entry is a decimal value. - MaxNumForwardPackets (REG_DWORD: 50) Establishes the maximum number of IP packet headers that can be allocated to the router packet queue. This value must be greater than or equal to the value of NumForwardPackets. This registry entry is a decimal value. These values can be modified in accordance with the instructions to allocate more resources for the forwarding buffer, but increasing them excessively will have a negative effect on other system resources. STATUS ====== Microsoft has confirmed this to be a problem in Windows NT version 4.0. Additional query words: TCPu UPCT poolmon ====================================================================== Keywords : Technology : kbWinNTsearch kbWinNTWsearch kbWinNTW400search kbWinNT400search kbWinNTW400sp4 kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400sp4 kbWinNTS400sp4 kbWinNTS400search Version : winnt:4.0 SP4 Issue type : kbbug Solution Type : kbnofix ============================================================================= 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 2002.