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

The company uses IP address reservations for file and print servers on their network. Reservations are used to create a permanent IP address lease assignment by the DHCP server. Reservations ensure that a specified hardware device on the subnet can always use the same IP address.

When using the 80/20 rule and splitting a scope’s IP address pool between two servers for load balancing and fault tolerance, identical reservations must be made at both DHCP servers. When reservations are made at both servers, neither server assigns the reserved IP address to another client, assuring that the intended device receives the address reserved for its use.

Table 2.3 shows two example address reservations. For more information about the 80/20 rule and for an example of how these reservations are created in specific scopes at each DHCP server, see "Scope Configuration" later in this chapter.

Table 2.3   Example Address Reservations

Device Subnet Reserved IP Address

Application server


File server



  • Reservations can be created using any IP address in the scope’s address range, even if the IP address is also within an exclusion range. Because of this design, when the 80/20 rule is implemented and some addresses in the scope are excluded (80 percent at one server, 20 percent at the other), reservations still function properly.