Virtual machine migration across network by publishing routes to the associated virtual networks via virtual router after the start of migration of the virtual machine

Abstract

Methods, systems and computer programs for migrating a virtual machine (VM) executing on a first host to a second host are presented, where the first host and the second are on different networks. One embodiment of a method includes assigning to the VM a VM address (VMA) belonging to a VM network and publishing a first route to an associated network (AN) via a first virtual router executing on the first host. The method further includes migrating the VM from the first host to the second host, the VM maintaining the assigned VMA after migrating, and publishing a second route to the AN via a second virtual router executing on the second host. The first and second virtual routers have addresses belonging to the VM network, and network packets to and from the VM flow through the virtual router where the VM is executing. A temporary tunnel between the virtual routers allows traffic to flow to the VM while the new route to AN is propagated throughout the network. The use of the associated network, which is associated with the VM, and the publishing of a new route to the VM allow the VM to keep the original VMA network address after the migration.