IP addresses can be either dynamic or static. Dynamic addresses are allocated by internet providers from their address pools and leased to customers for as long as their contract lasts, after which the address returns to the pool and can be reassigned. Static addresses are assigned to remain fixed but can also eventually be recycled and reassigned if unused for a long time, such as when an organization winds down its operations and its static address becomes available again. Both dynamic and static addresses can ultimately be recycled and reused over time as needed from the large pools of available IP addresses.