Unicast is any network communication between a single sender and a single receiver.
DHCP server responses typically use multicast communication to broadcast to all DHCP
clients within a limited broadcast address (e.g., 255.255.255.255). However, you can
configure the registry on Windows NT 4.0 or later DHCP servers to let clients request a
unicast response, rather than a multicast response, from the DHCP server by performing the following steps:

1. Start a registry editor (e.g., regedit.exe).
2. Navigate to the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DHCPServer\
   Parameters registry subkey.
3. Double-click IgnoreBroadcastFlag (or create this value of type DWORD if it doesn't already exist).
4. Set IgnoreBroadcastFlag to 1 to ignore the DHCP client request flag and always multicast responses or 0 to let the client choose between unicast or multicast, then click OK.
5. Close the registry editor.
6. Reboot the server.

Pre-NT 4.0 DHCP versions will ignore this registry setting.

How can I view DHCP address leases in Windows 2000?

When a client is offered and accepts an IP address a 'lease' is created for x amount of days. To view current leases perform the following:

1. Start the DHCP MMC snap-in (Start - Programs - Administrative Tools - DHCP)
2. Expand the server
3. Expand the scope whose leases you wish to view
4. Select the 'Address Leases' branch and in the right hand window you will see the current lease details.

It will give details of the IP address, client name and the lease expiration date. Expired leases are also shown for approximately one day but have a dimmed icon. This grace period protects a client lease in the event of the client and server being in different time zones, clocks not synced or simply offline.

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