Q. What types of virtual network can I create with Hyper-V?

A. Hyper-V supports three types of virtual network, each with its own uses and spheres of access. External virtual networks are bound to a physical NIC in the server. The parent and child partitions have access to the external network via the physical NIC and can communicate with one another. The child partitions each see a virtual network device, and the parent partition sees two network devices. The first is the physical NIC, which is bound only to the Microsoft Virtual Network Switch Protocol. The second network device is a virtual network switch adapter, which uses the external network for communication and is bound to the physical NIC.

Internal virtual networks aren’t bound to a physical NIC, so they can’t access any machine outside the physical server. An internal network is visible to the parent partition and the child partitions, so you can use it for communication between child partitions and between the child partitions and the parent partition. This can be useful if you’re hosting services on the parent partition, such as an iSCSI target, that you want the child partitions to be able to use. On both the parent and child partitions, a network device will be visible that represents the internal virtual network.

Private virtual networks are visible only on child partitions. Child partitions use them to communicate with one another.

The following diagram summarizes the access available for each of the network types.