Patent ID: 7769031

Claim:
A virtual machine system including a plurality of virtual machines constituted by a control program on a physical machine and virtual NIC (virtual network interface cards) for executing network communication between said plurality of virtual machines provided by said control program, said virtual machine system comprising: a virtual NIC controller for setting VLAN ID to said virtual NIC from said control program, and when said virtual NIC has received a packet, said virtual NIC controller confirming a VLAN ID set in a transmission side virtual NIC which transmitted said packet; and a VLAN (virtual local area network) manager for managing said VLAN ID set to said virtual NIC and a VLAN ID set by an OS (operating system) on one of said virtual machines that uses said virtual NIC, wherein said virtual NIC controller, when said VLAN ID is set to said transmission side virtual NIC, performs actions to: read out said VLAN ID of said transmission side virtual NIC; judges whether or not VLAN ID is set to a reception side virtual NIC; reads out VLAN ID of said reception side virtual NIC when VLAN ID is set to said reception side virtual NIC; and reports packet reception to a guest OS of a reception side virtual machine via said reception side NIC when VLAN ID of said transmission side virtual NIC coincides with VLAN ID of said reception side virtual NIC, wherein said guest OS reads a transmission packet sent from said transmission side virtual NIC as a reception packet.