Managing Clients and Leases
Applies To: Windows Server 2008
IP addresses are leased by the DHCP server to its clients. Each lease has an expiration date, which the client must renew if it is going to continue to use that address.
Leases are retained in the DHCP server database for four hours after they expire. This grace period protects a client lease in case the client and server are in different time zones, the individual computer clocks are not synchronized, or the client computer is off of the network when the lease expires. Expired leases are included in the list of active leases and are distinguished by a different icon.
You can delete a client lease of any DHCP client in the scope. The main reason for doing so is to remove a lease that conflicts with an IP address exclusion or a client reservation that you want to add. The effect of a deleted lease and an expired lease is the same: the next time that client computer starts, it must enter the initialization state and obtain new TCP/IP configuration information from a DHCP server. There is nothing, however, to prevent the client from obtaining a new lease for the same IP address. You must make the address unavailable before the client requests another lease. For more information, see Delete a Client Lease.
Delete only entries for clients that are no longer using the assigned DHCP lease or that are to be moved immediately to a new address. Deleting an active client can result in duplicate IP addresses on the network because deleted addresses will be assigned to new active clients. After you delete the lease of the client and set a reservation or exclusion, you should always use ipconfig /release on the client computer to force the client to free its IP address. For more information about managing leases with ipconfig, see Verify, Release, or Renew a Client Address Lease and View Client Lease Information.
You can view lease information for individual clients by first selecting the Active Leases folder for a scope in the DHCP console. When Active Leases for a scope is selected as the console view, the list of currently active client leases for the scope appears in the details pane.