A superscope is an administrative feature of DHCP servers running Windows Server 2003 that you can create and manage through the DHCP console. Using a superscope, you can group multiple scopes as a single administrative entity. With this feature, a DHCP server can:

• Support DHCP clients on a single physical network segment (such as a single Ethernet LAN segment) where multiple logical IP networks are used. When more than one logical IP network is used on each physical subnet or network, such configurations are often called multinets.
  
  
• Support remote DHCP clients located on the far side of DHCP and BOOTP relay agents (where the network on the far side of the relay agent uses multinets).
  
  

In multinet configurations, you can use DHCP superscopes to group and activate individual scope ranges of IP addresses used on your network. In this way, the DHCP server computer can activate and provide leases from more than one scope to clients on a single physical network.

Superscopes can resolve certain types of DHCP deployment issues for multinets, including situations in which:

• The available address pool for a currently active scope is nearly depleted, and more computers need to be added to the network. The original scope includes the full addressable range for a single IP network of a specified address class. You need to use another IP network range of addresses to extend the address space for the same physical network segment.
  
  
• Clients must be migrated over time to a new scope (such as to renumber the current IP network from an address range used in an existing active scope to a new scope that contains another IP network range of addresses).
  
  
• You want to use two DHCP servers on the same physical network segment to manage separate logical IP networks.
  
  

The following section shows how a simple DHCP network consisting originally of one physical network segment and one DHCP server, can be extended to use superscopes for support of multinet configurations.

In this preliminary instance, a small local area network (LAN) with one DHCP server supports a single physical subnet, Subnet A. The DHCP server in this configuration is limited to leasing addresses to clients on this same physical subnet.

The following illustration shows this example network in its original state. At this point, no superscopes have been added and a single scope, Scope 1, is used to service all DHCP clients on Subnet A.

To include multinets implemented for client computers on Subnet A, the same network segment where the DHCP server is located, you can configure a superscope which includes as members: the original scope (Scope 1) and additional scopes for the logical multinets for which you need to add support (Scope 2, Scope 3).

This illustration shows the scope and superscope configuration to support the multinets on the same physical network (Subnet A) as the DHCP server.

To include multinets implemented for client computers on Subnet B, the remote network segment located across a router from the DHCP server on Subnet A, you can configure a superscope which includes as members: the additional scopes for the logical multinets for which you need to add remote support (Scope 2, Scope 3).

Note that since the multinets are for the remote network (Subnet B), the original scope (Scope 1) does not need to be part of the added superscope.

This illustration shows the scope and superscope configuration to support the multinets on the remote physical network (Subnet B) away from the DHCP server.

Note

• A DHCP relay agent is used for DHCP servers to support clients on remote subnets, as shown in Example 3. For more information, see Understanding relay agents.