System Administration Guide: IP Services

Dynamic and Permanent Lease Types

The lease type determines whether the lease policy applies to the IP addresses you are configuring. During initial server configuration, DHCP Manager allows you to select either dynamic or permanent leases for the addresses you are adding. If you configure the DHCP server with the dhcpconfig command, leases are dynamic.

When an IP address has a dynamic lease, the DHCP server can manage the address. The DHCP server can allocate the IP address to a client, extend the lease time, detect when the address is no longer in use, and reclaim the address. When an IP address has a permanent lease, the DHCP server can only allocate the address. The client then owns the address until explicitly releasing the address. When the address is released, the server can assign the address to another client. The address is not subject to the lease policy as long as the address is configured with a permanent lease type.

When you configure a range of IP addresses, the lease type you select applies to all the addresses in the range. To get the most benefit from DHCP, you should use dynamic leases for most of the addresses. You can later modify individual addresses to make them permanent, if necessary. However, the total number of permanent leases should be kept to a minimum.