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Q139415: New TCP/IP ArpCacheLife Parameter in Windows NT

Article: Q139415
Product(s): Microsoft Windows NT
Version(s): winnt:3.51,4.0
Operating System(s): 
Keyword(s): kbsetup
Last Modified: 08-AUG-2001

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The information in this article applies to:

- Microsoft Windows NT Workstation versions 3.51, 4.0 
- Microsoft Windows NT Server versions 3.51, 4.0 
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SUMMARY
=======

In Windows NT 3.5 and 3.51 Service Pack 3 or earlier, an ARP cache entry times
out in 2 minutes. If the same entry is used again, the time-out period is 10
minutes. The time-out entry is not user configurable.

With Windows NT version 3.51 Service Pack 4 or later, a new parameter,
ArpCacheLife, allows ARP cache life to be configured.

If the new ArpCacheLife parameter is not present, the following defaults are
used. Windows NT arp cache time-out defaults to 2 minutes if the entry is not
used and 10 minutes if it is reused.

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


ArpCacheLife is found in the HKEY_LOCAL_MACHINE\SYSTEM subtree, in the following
key:

  \CurrentControlSet\Services\Tcpip\Parameters

  The parameter information is as follows:

  Entry: ArpCacheLife
  Type: REG_DWORD
  Range: Number of Seconds

ArpCacheLife determines the default lifetime in seconds for entries in the ARP
cache table. Once an entry is placed in the ARP cache, it is deleted after it is
allowed to remain there until its lifetime expires or until its table entry is
reused because it is the oldest entry. In absence of an ArpCacheLife parameter,
the default for ARP cache time-outs is a 2 minute time-out on unused entries and
a 10 minute time-out on used entries.

The initial ArpCacheTable is large enough for 50 entries. When there are 50
entries, the ARP cache is allowed to grow dynamically.

RESOLUTION
==========

This problem has been corrected in the latest Service Pack for Windows NT
version 3.51 and Windows NT 4.0 or later.

STATUS
======

Microsoft has confirmed this to be a problem in Windows NT versions 3.5 and 3.51
Service Pack 3 or earlier. This problem was corrected in Windows NT version 3.51
U.S. Service Pack 4. For information on obtaining the Service Pack, query on the
following word in the Microsoft Knowledge Base (without the spaces):

  S E R V P A C K


Additional query words: prodnt

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Keywords          : kbsetup 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT351search kbWinNT400search kbWinNTW351search kbWinNTW351 kbWinNTSsearch kbWinNTS400search kbWinNTS400 kbWinNTS351 kbWinNTS351search
Version           : winnt:3.51,4.0

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