The network connection of a VM (target VM) that has been live-migrated from a first physical computer to a second physical computer is restored in a virtual computer system in which communication is performed using a certain type of information outside the jurisdiction of a virtualization mechanism. When receiving a packet from the VM, the first virtualization mechanism of the first physical computer extracts a certain type of information from the packet and registers the extracted certain type of information in a first management information unit. The first virtualization mechanism transmits the certain type of information in the first management information unit to the second virtualization mechanism of the second physical computer during live migration. The second virtualization mechanism registers the certain type of information in a second management information unit and transmits a certain type of packet including the certain type of information from at least one of one or more physical I/O devices of the second physical computer in order to restore the network connection of the target VM.