1. A method for migrating a virtual machine (VM) across virtual networks from a source distributed virtual switch on a source host machine in a first virtual network where a virtual network adapter of the VM is connected to a first distributed virtual port of the source distributed virtual switch to a destination distributed virtual switch on a destination host machine in a second virtual network, wherein the source distributed virtual switch is distinct from the destination distributed virtual switch, comprising: reserving, prior to migrating the VM from the source host machine to the destination host machine, a second distributed virtual port on the destination distributed virtual switch for the virtual network adapter of the VM; receiving, at the destination host machine, a copy of a configuration of the VM from the source host machine; modifying, at the destination host machine, the copy of the configuration of the VM as to reference the second distributed virtual port instead of the first distributed virtual port; receiving a copy of network state data of the first distributed virtual port; applying the copy of network state data to the second distributed virtual port on the destination distributed virtual switch; and subsequent to migrating the VM from the source host machine to the destination host machine, connecting the virtual network adapter of the VM to the second distributed virtual port on the destination distributed virtual switch.