KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q166750: ARP Cache Entries May Not Time Out for 10 Minutes

Article: Q166750
Product(s): Microsoft Windows NT
Version(s): winnt:4.0
Operating System(s): 
Keyword(s): kbnetwork
Last Modified: 08-AUG-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Windows NT Workstation version 4.0 
- Microsoft Windows NT Server version 4.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

If the media access control address changes for an IP address that a Windows NT
computer is communicating with, the Windows NT computer may not be able to
communicate to or through the device for up to 10 minutes.

CAUSE
=====

Windows NT 4.0 offers a configurable ArpCacheLife registry parameter. This
parameter controls the arpcache life for entries that are not being referenced
in the arpcache. Windows NT computers reference an arpcache entry each time an
outbound IP packet is sent to the address described by the entry.

Entries being referenced time out after 10 minutes, and this time out value is
not adjustable. If you are communicating with a device that has some form of
hardware fail-over capability that does not update the arpcache on the other
devices on the network, its media access control address may change, and if
there is a steady stream of traffic being directed at it by applications on a
Windows NT computer, the arpcache entry may not time out for this 10 minute
period.

RESOLUTION
==========

To resolve this problem, either obtain the hotfix mentioned in the STATUS
section of this article, or wait for the next Windows NT service pack.

NOTE: Service Pack 3 must be applied to Windows NT 4.0 before applying the
hotfix.

The hotfix should have the following timestamp:

  (i386)  12/01/97  04:24p    143,632 Tcpip.sys
  (alpha) 12/01/97  04:21p    263,472 Tcpip.sys

STATUS
======

Microsoft has confirmed this to be a problem in Windows NT version 4.0.

A supported fix is now available, but has not been fully regression-tested and
should be applied only to systems experiencing this specific problem. Unless you
are severely impacted by this specific problem, Microsoft recommends that you
wait for the next Service Pack that contains this fix. Contact Microsoft
Technical Support for more information.



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

With the hotfix, a new version of Tcpip.sys is available, that allows greater
control over arpcache life, as described below:

Value: ArpCacheMinReferencedLife
Key:
Hkey_Local_Machine\System\CurrentControlSet\Services\ 
\Tcpip\Parameters

Value Type: REG_DWORD
Valid Range: 0-0xffffffff
Default: 600 seconds (10 minutes)

Description: ArpCacheMinReferencedLife controls the minimum time that a
referenced arpcache entry will expire in. This parameter can be used in
combination with the ArpCacheLife parameter, as follows:

If ArpCacheLife >= ArpCacheMinReferencedLife, referenced and unreferenced
arpcache entries will expire in "ArpCacheLife" seconds.

If ArpCacheLife < ArpCacheMinReferencedLife, unreferenced entries will expire
in "ArpCacheLife" seconds, and referenced entries will expire in
"ArpCacheMinReferencedLife" seconds.

For additional information about the ArpCacheLife registry parameter, click the
article number below to view the article in the Microsoft Knowledge Base:

  Q139415 New TCP/IP ArpCacheLife Parameter in Windows NT

Additional query words: arp cache proxy MAC resolution protocol

======================================================================
Keywords          : kbnetwork 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400
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.