A management program comprising a plurality of executable instructions, which, when executed on a computer, cause the computer to execute a process comprising: receiving a tunnel connection command to connect a first virtual machine (123; 629) and a second virtual machine (142; 630) through a layer 2 tunnel corresponding to particular quality of service; characterized in that the process further comprises: instructing (S106; S107) a first physical machine (120; 652) on which the first virtual machine (123;629) is running and which is connected to a plurality of physical networks (170, 171, 172) through a first physical network interface device to use a first address and a second address in encapsulating in a first layer 3 packet a first layer 2 frame that the first virtual machine decides to send to the second virtual machine, each of the plurality of physical networks supporting one or more levels in quality of service, both the first address and the second address corresponding to a particular physical network of the plurality of physical networks that supports the particular quality of service, the first address being one of a plurality of addresses (I1, I2, I3) assigned to the first physical network interface device, and the second address being one of a plurality of addresses (I4, I5, I6) assigned to a second physical network interface device through which a second physical machine (140; 653) on which the second virtual machine (142; 630) is running is connected to the plurality of physical networks; and instructing (S106; S107) the second physical machine to use the second address and the first address in encapsulating in a second layer 3 packet a second layer 2 frame that the second virtual machine decides to send to the first virtual machine. receiving a tunnel connection command to connect a first virtual machine (123; 629) and a second virtual machine (142; 630) through a layer 2 tunnel corresponding to particular quality of service; characterized in that the process further comprises: instructing (S106; S107) a first physical machine (120; 652) on which the first virtual machine (123;629) is running and which is connected to a plurality of physical networks (170, 171, 172) through a first physical network interface device to use a first address and a second address in encapsulating in a first layer 3 packet a first layer 2 frame that the first virtual machine decides to send to the second virtual machine, each of the plurality of physical networks supporting one or more levels in quality of service, both the first address and the second address corresponding to a particular physical network of the plurality of physical networks that supports the particular quality of service, the first address being one of a plurality of addresses (I1, I2, I3) assigned to the first physical network interface device, and the second address being one of a plurality of addresses (I4, I5, I6) assigned to a second physical network interface device through which a second physical machine (140; 653) on which the second virtual machine (142; 630) is running is connected to the plurality of physical networks; and instructing (S106; S107) the second physical machine to use the second address and the first address in encapsulating in a second layer 3 packet a second layer 2 frame that the second virtual machine decides to send to the first virtual machine. instructing (S106; S107) a first physical machine (120; 652) on which the first virtual machine (123;629) is running and which is connected to a plurality of physical networks (170, 171, 172) through a first physical network interface device to use a first address and a second address in encapsulating in a first layer 3 packet a first layer 2 frame that the first virtual machine decides to send to the second virtual machine, each of the plurality of physical networks supporting one or more levels in quality of service, both the first address and the second address corresponding to a particular physical network of the plurality of physical networks that supports the particular quality of service, the first address being one of a plurality of addresses (I1, I2, I3) assigned to the first physical network interface device, and the second address being one of a plurality of addresses (I4, I5, I6) assigned to a second physical network interface device through which a second physical machine (140; 653) on which the second virtual machine (142; 630) is running is connected to the plurality of physical networks; and instructing (S106; S107) the second physical machine to use the second address and the first address in encapsulating in a second layer 3 packet a second layer 2 frame that the second virtual machine decides to send to the first virtual machine.