New TCP/IP ArpCacheLife Parameter in Windows NT 3.51 SP4

 Last reviewed: March 24, 1997
Article ID: Q139415

The information in this article applies to:
  • Microsoft Windows NT Workstation version 3.51
  • Microsoft Windows NT Server version 3.51
  • Microsoft Windows NT Server version 4.0
  • Microsoft Windows NT Workstation version 4.0

SUMMARY

Previously, in Windows NT 3.5 and 3.51, an ARP cache entry times out in 2 minutes. If the same entry is used again, the time-out period is 10 minutes. It is not user configurable.

With Windows NT version 3.51 and Service Pack 4 (or greater), 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.

STATUS

Microsoft has confirmed this to be a problem in Windows NT versions 3.5 and 3.51. This problem was corrected in the latest Windows NT version 3.51 U.S. Service Pack. 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
Keywords : kbbug3.51 kbfix3.51.sp4 kbsetup NTSrvWkst nttcp
Version : 3.5 3.51 4.0
Platform : WinNT

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Last reviewed: March 24, 1997
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