Creating Reservations

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. For example, if you have defined the range 192.168.1.11 through 192.168.1.254 as your DHCP scope, you can then reserve the IP address 192.168.1.100 within that scope for the network adapter whose hardware address is 00- b0-d0-01-18-86. Every time the computer hosting this adapter boots, the server recognizes the adapter's Media Access Control (MAC) hardware address and leases the same address 192.168.1.100.

To create a reservation within the DHCP console, open the scope in which you want to create a reservation, right-click Reservations, and then select New Reservation. This procedure opens the New Reservation dialog box. To configure a reservation, you must type appropriate values into the Reservation Name, IP Address, and MAC Address text boxes.

Reservations cannot be used interchangeably with manual (static) configurations. Certain computers, such as those hosting a DNS server or a DHCP server, require their IP addresses to be configured manually and not automatically by means of a DHCP server. In such cases, reservations are not a valid alternative to static configurations.

However, you can use a reservation when you want to assign a specific address to a non-essential computer. Through this method, you can dedicate an address while still enjoying the other benefits of DHCP, including centralized management, address conflict prevention, and scope option assignment. For example, you might find that a print server's specific IP address configuration is more easily managed through a centrally configured reservation, which is continually renewed, than through a manual configuration locally at the server. Finally, you should remember that reservations can be made only to DHCP clients. In other words, a DHCP server can lease a reservation only to clients that have been configured to obtain an IP address automatically.

Tip Look for questions in which a particular address is simultaneously reserved and excluded. In such cases, the reservation can't work.