DHCP Clients' Ability to Send DHCPDECLINE Message


In the current implementation of the Microsoft dynamic host configuration protocol (DHCP) service, if a device is provided with an Internet Provider (IP) configuration by way of DHCP, we do a courtesy Address Resolution Protocol (ARP) with the provided IP address. If anyone responds, that means the address is in use. In this case, when a duplicate IP is detected as the TCP/IP protocol tries to initialize, a popup message is provided to the user stating that a duplicate IP address exists. The user is informed to get system administration assistance. At that point, the TCP/IP protocol initialization is failed and the user can't access any network resources.

More Information

DHCP RFC 1541 permits that instead of informing the user, initiating a manual process, a DHCP_DECLINE transaction can be returned to the DHCP server. The server will then allocate a different IP address for the device.

DHCP RFC 1541 indicates that it is the responsibility of the DHCP client to notify the DHCP server with a DHCP_DECLINE transaction if the client determines that there is a problem with the DHCP parameters provided by the DHCP Server.

The RFC states:
3.1 Client-server interaction - allocating a network address:

The client receives the DHCPACK message with configuration parameters. The client performs a final check on the parameters and notes the duration of the lease and of the lease identification cookie specified in the DHCPACK message. At this point, the client is configured. If the client detects a problem with the parameters in the DHCPACK message, the client sends a DHCPDECLINE message to the server and restarts the configuration process. The client should wait a minimum of ten seconds before restarting the configuration process to avoid excessive network traffic in case of looping.

4.3.3 DHCPDECLINE message:

If the server receives a DHCPDECLINE message, the client has discovered through some other means that the suggested network address is already in use. The server MUST mark the network address as "not allocated" and SHOULD notify the local system administrator of a possible configuration problem.
The Windows 95/98 Downlevel DHCP Clients have also been updated to include DHCPDECLINE functionality. Windows 98 includes the DHCPDECLINE ability. For Windows 95, please refer to either of the following articles:
ARTICLE-ID: 191494
TITLE : Dial-Up Networking 1.3 Upgrade Available

ARTICLE-ID: 182108
TITLE : Availability of Windows Sockets 2.0 for Windows 95


Microsoft has confirmed this to be a problem in Windows NT version 4.0. This problem was corrected in the latest US Service Pack for Windows NT. For information on obtaining this update, query on the following word in the Microsoft Knowledge Base (without the spaces):