After investigation virtual machines off the network trigger physical machine migration strategy, then moved back from node migrated unavailable

After investigation virtual machines off the network trigger physical machine migration strategy, then moved back from node migrated unavailable
Experiment:

  1. Node1 physical machines running virtual machines vm_test
  2. Unplug the network cable node1 physical machine, using virsh list --all view a running virtual machine vm_test
  3. Wait for the virtual machine to a physical machine migration vm_test node2
  4. Virtual machine migration to node2 success vm_test
  5. were in the physical machine node1, use node2 virsh list --all view a running virtual machine,At this time, vm_test exist in the physical machine node1 and node2, and run simultaneously.Then again vm_test want to migrate from node2 back to node1, certainly fail.(Performing dynamic migration, is the name of the client migration is unique on the host does not have a purpose and source host are migrated clients with the same name exist in the client)
  6. Manual destroy physical machine node1 virtual machine vm_test, again migrating from a physical machine to node1 node2 vm_test, successful migration.

Issue:
I have read the code, after pulling off the network cable is redeployment, rather than migration,Why opennebula not designed to migrate off the net rather than the redeployment?