Internet protocol address reassignment between virtual machine instances

In various methods and apparatus Internet Protocol (IP) addresses can be moved between virtual machine instances in a provider network. Customers can cause an IP address to be moved between virtual machine instances such as by submitting an application programming interface call. The provider network also may include a server system that implements the dynamic host configuration protocol such as the DHCP for version 6. The DHCP server system moves the requested IP address by exchanging messages with the effected instances. The DHCP server system may transmit a message to remove the IP address from a first instance by including the IP address with a valid lifetime set to a minimal time-out value. The DHCP server system may transmit a message to add the IP address to a second instance by including the IP address and a corresponding valid lifetime value of greater than the minimal time-out value.