In previous versions of Windows, a DHCP client would continue to use a leased address, until the lease expired, even if they were unable to connect to the DHCP server and default gateway.
In Windows 2000, if a client looses connectivity to a DHCP server and default gateway, they receive an APIPA (Automatic Private IP Addressing) IP address, until connectivity is restored. The client periodically sends DHCP discovery packets and then ARPs for the default gateway.
To determine if this has happend, open a CMD prompt and type ipconfig. If the IP address is in the APIPA Class B range, 169.254.0.0 to 169.254.255.255, they are unable to reach the DHCP server and default gateway.
If you wish to revert to the old behavior, disable APIPA on a specific adapter or for the entire computer.Use Regedt32 to navigate to or create:
Disable APIPA on a specific NIC
On the Edit menu, Add Value name IPAutoconfigurationEnabled, as a REG_DWORD data type, and set the data value to 0. The default (missing) value is 1, which enables APIPA on this interface.
Disable APIPA on the Entire Computer
On the Edit menu, Add Value name IPAutoconfigurationEnabled, as a REG_DWORD data type, and set the data value to 0. The default (missing) value is 1, which enables APIPA on ALL interfaces.
NOTE: You must restart the client for the change to take effect.