This article was previously published under Q219374
When a Windows NT-based computer starts, a packet is broadcast on the network containing the computer's TCP/IP address to prevent the use of duplicate addresses on the same network. This is called a gratuitous Address Resolution Protocol (ARP) packet. Routers and other network hardware may cache routing information gained from multiple gratuitous ARP packets. For both performance and maintenance reasons, it is possible to disable this feature in Windows NT.
To resolve this problem, obtain the latest service pack for Windows NT 4.0. For additional information, click the following article number to view the article in theMicrosoft Knowledge Base:
152734 How to Obtain the Latest Windows NT 4.0 Service Pack
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Windows NT 4.0 Service Pack 5.
To disable gratuitous ARPs after applying this hotfix:
Click Start, click Run, type regedt32, and then click OK.
On the Windows menu, click HKEY_LOCAL_ MACHINE on Local Machine.
Click the \System\CurrentControlSet\Services\TcpIp\Parameters folder.
Double-click the ArpRetryCount value, type 0, (for Windows 2000, type 1) and then click OK.
Quit Registry Editor, and then restart the computer.
For additional information about gratuitous ARPs, click the article number below to view the article in the Microsoft Knowledge Base:
199773 Behavior of Gratuitous ARP in Windows NT 4.0