Configuring a Microsoft Windows NT 4.0 DHCP Server for Unicast

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This article was previously published under Q161429

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SUMMARY

By default, the Microsoft Windows NT 4.0 DHCP server sends all DHCP responses as IP broadcasts to the limited broadcast address (255.255.255.255). However, the DHCP server can be configured to unicast responses if the client request specifies that a broadcast response is not required.

MORE INFORMATION

Versions of the DHCP server prior to Windows NT 4.0 ignored the broadcast flag in client DHCP packets, and broadcast all replies. Version 4.0 of the DHCP server supports unicasting via the following registry parameter:
HKEY_LOCAL_MACHINE \CurrentControlSet \Services \DHCPServer \Parameters \IgnoreBroadcastFlag

Parameter Type: REG_DWORD
Default: 1
Description: If set to 1, the broadcast flag in client requests is ignored, and all DHCP packets are broadcast from the server. If set to 0, the behavior (whether to broadcast or not) is controlled by the broadcast flag in the client request that is being responded to.

The Networks.wri file also contains a description of this parameter.