1. A method for controlling live migration of a virtual machine from a first host to a second host, the method comprising: executing, by the first and second hosts, respective virtualization modules, the first and second hosts among a plurality of hosts with respective virtualization modules, the virtualization modules managed by a virtual machine manager, each host having a respective host network address and having virtual machines with respective virtual network addresses, wherein the hosts exchange packets via a network using their respective host network addresses; prior to a determination to migrate a virtual machine, storing instances of a first mapping policy on the plurality of hosts, respectively, wherein each instance of the first mapping policy comprises the virtual network addresses and the host network addresses, wherein each instance of the first mapping policy indicates which of the virtual network addresses therein are associated with which of the host network addresses therein, and wherein prior to the determination to migrate the virtual machine, each virtualization module handles incoming packets from the network addressed to its host network address and handles outgoing packets sent by its virtual machines to other virtual network addresses, and prior to the determination to migrate the virtual machine, each virtualization module uses a respective instance of the first mapping policy to determine which of its virtual machines are to receive which of the incoming packets, and during the migration and prior to the determination to migrate the virtual machine, each virtualization module uses a respective instance of the first mapping policy to determine which host network addresses to send the outgoing packets to; making the determination, by the virtual machine manager, to migrate the virtual machine, wherein the virtual machine is determined to be migrated from the first host to the second host; responsive to and in conjunction with the determination to migrate the virtual machine, and prior to completion of the migrating, sending, to the hosts in the plurality, respective instances of a second mapping policy comprising the virtual network address of the virtual machine and the host network address of the second host, each instance of the second mapping policy indicating that the virtual network address is associated with the host network address of the second host, wherein during the migration the instances of the second mapping policy are in an inactive state; after migration of the virtual machine completes, notifying the plurality of hosts to activate their respective instances of the second mapping policy for communicating with the virtual machine; in response to the notifying, the instances of the second mapping policy begin entering active use by the plurality of hosts for communicating with the virtual machine; and in response to the notifying, forwarding, by the first host, any packets for the virtual machine that are received by the first host while the instances of the second mapping policy are entering active use.