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How to Request Additional DHCP Options from a DHCP Server
Article ID: 312468 - View products that this article applies to.
This article was previously published under Q312468
This article describes how to configure the DHCP Client service to request additional DHCP options (for example, option 11 [Resource Server]) and describes some differences between Windows NT 4.0 and Windows 2000.
All of the Windows DHCP client computers that are referenced in this article support the following DHCP options by default:
In addition, Windows 2000 supports option 31 (Perform Router Discovery) and option 33 (Static Route).
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Windows NT 4.0Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/322756/ )How to back up and restore the registry in Windows
In Windows NT 4.0, the DHCP options are stored in the following registry key:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\DHCP\Parameters\OptionsYou can add a new key for the DHCP option that you want to request from the DHCP server. Options that are supported by the DHCP server are defined in Request for Comments (RFC) 1533. For example, if you want to request the Internet protocol (IP) address for a resource server, you must add DHCP option 11. To do so:
Windows 2000The DHCP Client service in Windows 2000 has been updated from Windows NT 4.0. Windows 2000 clients must make a DhcpRequestParams API call to request custom parameters. The DHCP client stores data that is obtained from a DHCP server in its local cache. If the DHCP client cache contains all of the data that is requested in the pRecdParams array of a DhcpRequestParams function call, the client returns data from its cache.
If the data that is requested is not available in the client cache, the client processes the DhcpRequestParams function call by submitting a DHCP-INFORM message to the DHCP server. The DhcpRequestParams API call can also be used to request User or Vendor ClassID-based options. For more information, refer to Microsoft Developer Network (MSDN) documentation about the API call. You can find examples of code in the following MSDN documents:
RFC 1533 - DHCP Options and BOOTP Vendor Extensions
Article ID: 312468 - Last Review: September 14, 2007 - Revision: 3.4