Understanding user and vendor classes

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Understanding user and vendor classes

There are significant differences in the way in which vendor and user classes are available for use by DHCP clients and servers. The following table compares and contrasts the features of these classes.

User classes Vendor classes

Part of proposed DHCP standard drafts.

For updated information, obtain the latest draft from the Request for Comments Web site.

Part of accepted DHCP standard drafts (RFC 2131, 2132).

Clients identify user class membership with User class information.

Clients identify vendor class membership by using the Vendor class identifier option.

User class IDs can be set and viewed at DHCP clients running Windows 2000, Windows XP, or Windows Server 2003 operating systems using the ipconfig command.

For more information, see:

Vendor class IDs are configured internally by DHCP client system vendors, such as Microsoft and other vendors.

When adding a vendor class at the server, you need to specify class data at the server that matches identically the class ID used by same-vendor clients. For more information, contact the applicable vendor.

With user classes, you can take advantage of predefined classes that can be used to support specialized groups of clients, such as BOOTP or Routing and Remote Access clients.

With vendor classes, Microsoft has implemented vendor classes to the provided classification of its DHCP clients by Windows 98, Windows 2000, or Microsoft DHCP clients which share the use of the Microsoft-reserved vendor prefix ("MSFT") in any class-related data used.

User classes are typically created for administrative reasons, such as to identify all DHCP clients in a specific site or location.

For example, all computers and printers located on the same floor in an office building might be assigned or configured as part of the same user class.

Vendor classes are typically created for the enhancement of vendor-specific DHCP functionality.

For example, Microsoft provides several additional vendor-specific options, such as the ability to disable NetBIOS over TCP/IP at DHCP clients running Windows 2000 or Windows XP.

User classes are most helpful to users for managing DHCP option assignments based on their needs.

If your DHCP network is large enough to benefit from user classes, you can freely customize your DHCP environments with them. In most cases, the user class provides a way to assign and override standard DHCP option values set at either the server, scope, or reserved client level.

Vendor classes are most helpful to vendors for managing DHCP option assignments based on vendor-specific needs without disturbing other non-vendor DHCP clients.

With a vendor class, options are passed to clients using the Vendor specific information option, which encapsulates the options it sends. This helps non-vendor clients to recognize the information as vendor-specific and ignore and discard it as needed.