1. A method of virtualization of a source data center, comprising: creating a backup image of each of a plurality of computers in a source data center, the plurality of computers being connected to a network having a network topology, each backup image comprising a snapshot of the corresponding computer, the snapshot comprising an application-consistent image as of a specific point in time of primary storage of the corresponding computer; collecting network connection state information of each of the plurality of computers by a plurality of metadata collection agents, each of the plurality of metadata collection agents being resident on one of the plurality of computers; saving together with each backup image, supplemental to each backup image, the network connection state information of the corresponding computer; loading the backup images as virtual machines in a cloud computing node; creating a software defined network, wherein creating the software defined network comprises creating vendor-specific configuration or image files adapted for instantiating cloud resources; loading the network connection state information saved together with the backup images, and using the network connection state information to recreate the network connections of each of the plurality of computers; and emulating the source data center with said virtual machines, thereby providing a substitute data center.