By using reservations, you can reserve specific IP addresses for permanent use by a DHCP-enabled computer or device.
If multiple DHCP servers are each configured with scopes that cover a range of addresses that must be reserved, the reservation ranges must be specified on each DHCP server. Otherwise, those addresses could be given out by another DHCP server.
If you want to change a reserved address for a client, the client's existing address reservation must be removed before the new reservation can be added. DHCP option information can be changed while still keeping the reserved IP address.
Reserving a scope IP address does not automatically force a client currently using that address to stop using it. If you are reserving a new address for a client, or an address that is different from the client's current one, you should verify that the address has not already been leased. If the address is already in use, the client using the address must release it by issuing a DHCPRelease request. To achieve this, run ipconfig /release at a command prompt.
Reserving an address does not force the client for whom the reservation is made to immediately move to using the reserved address. The client must issue a renewal request to move to the newly reserved address. To achieve this, run ipconfig /renew at a command prompt.
For Windows 95 or Windows 98–based clients, use the Winipcfg.exe program to force the release or renewal of the reserved address. For clients using MS-DOS or other operating systems, restart the clients to force the change.
Once a release or renewal is complete, the reserved client is leased the newly reserved IP address for its permanent use.