DHCP terminology

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

DHCP terminology

Term Description


A scope is the full consecutive range of possible IP addresses for a network. Scopes typically define a single physical subnet on your network to which DHCP services are offered. Scopes also provide the primary way for the server to manage distribution and assignment of IP addresses and any related configuration parameters to clients on the network.


A superscope is an administrative grouping of scopes that can be used to support multiple logical IP subnets on the same physical subnet. Superscopes only contain a list of member scopes or child scopes that can be activated together. Superscopes are not used to configure other details about scope usage. For configuring most properties used within a superscope, you need to configure member scope properties individually.

exclusion range

An exclusion range is a limited sequence of IP addresses within a scope, excluded from DHCP service offerings. Exclusion ranges assure that any addresses in these ranges are not offered by the server to DHCP clients on your network.

address pool

After you define a DHCP scope and apply exclusion ranges, the remaining addresses form the available address pool within the scope. Pooled addresses are eligible for dynamic assignment by the server to DHCP clients on your network.


A lease is a length of time that a DHCP server specifies, during which a client computer can use an assigned IP address. When a lease is made to a client, the lease is active. Before the lease expires, the client typically needs to renew its address lease assignment with the server. A lease becomes inactive when it expires or is deleted at the server. The duration for a lease determines when it will expire and how often the client needs to renew it with the server.


You use a reservation to create a permanent address lease assignment by the DHCP server. Reservations assure that a specified hardware device on the subnet can always use the same IP address.

option types

Option types are other client configuration parameters a DHCP server can assign when serving leases to DHCP clients. For example, some commonly used options include IP addresses for default gateways (routers), WINS servers, and DNS servers. Typically, these option types are enabled and configured for each scope. The DHCP console also permits you to configure default option types that are used by all scopes added and configured at the server. Most options are predefined through RFC 2132, but you can use the DHCP console to define and add custom option types if needed.

options class

An options class is a way for the server to further manage option types provided to clients. When an options class is added to the server, clients of that class can be provided class-specific option types for their configuration. For Microsoft® Windows® 2000 and Windows XP, client computers can also specify a class ID when communicating with the server. For earlier DHCP clients that do not support the class ID process, the server can be configured with default classes to use instead when placing clients in a class. Options classes can be of two types: vendor classes and user classes.