Windows 8 : Using Hyper-V - Configuring virtual machine networking and storage (part 2) - Hyper-V virtual switch

Hyper-V virtual switch

As mentioned previously, the Hyper-V virtual switch can operate three modes: external, internal, and private. Each of these switch modes has different characteristics that need to be considered before placing VMs on them.

By far, the external virtual switch type is the most commonly used option. External mode places a virtual machine (with its 00-15-5D-xx-xx-xx MAC address) on the same Ethernet network as the computer running Windows 8 with the Hyper-V feature enabled. When this happens, the virtual machine can communicate with other network systems and externally with the Internet if routed correctly. The TCP/IP address will also be the same as physical systems in this configuration. Other networking protocols can also be used. The external mode operates much like an uplink function on a physical switch.

The external virtual switch type has granular configuration options, which can be important if technologies such as virtual local area networks (VLANs) are used in your environment. If a VLAN configuration is necessary, the Hyper-V virtual switch can deliver multiple external virtual switches on multiple VLANs—much like the Hyper-V configuration found frequently in Windows Server 2012 virtualized infrastructures. The external virtual switch can use dedicated interfaces or can share traffic with the computer running Windows 8 with the Hyper-V feature enabled, as shown in Figure 3.

Figure 3. The external network and sharing the network adapter

The internal virtual switch type (Figure 4) enables virtual machines to interact with the computer running Windows 8 with the Hyper-V feature enabled and with one another but does not allow communication with the physical network. This is good when you need to move files between the virtual machines and the Windows 8–based computer; however, you might not want to allow the virtual machines to communicate externally. Network placement situations with earlier operating systems without critical updates and service packs might not be desirable. With the internal virtual switch, their presence is off the physical network.

If the virtual machines on the internal switch type need to interact with resources on the network or Internet when the external type is not an option, it might be possible to have software on the Windows 8–based computer with the Hyper-V feature enabled run a router or proxy service. In this manner, outbound traffic to the network would be sent directly from the computer running Windows 8 and not from the virtual machines (as is the case with the external virtual switch type). Traffic on the internal switch type does not travel on an actual network interface; it is provided by the Hyper-V engine itself. This situation might arise when there are restrictions on the physical network of what type of systems can be connected; also, the virtual machines might not meet the requirements for the network (security, updates, operating system type, and so on).

Figure 4. Internal type limiting traffic for virtual machines to the computer running Windows 8 with the Hyper-V feature enabled and the virtual machines

The last type option for the Hyper-V virtual switch is the private type (see Figure 5), which keeps traffic contained to the virtual machines on the computer running Windows 8 with the Hyper-V feature enabled. Although the Windows 8–based computer provides the virtual switch for the virtual machines, it is not connected to it. In this situation, the only way to interact with the virtual machines is to use the Virtual Machine Connection screen to access the virtual console. The private type is useful for specific and isolated testing situations when minimal networking is required.

Figure 5. Private type limiting VM network traffic to VMs on the computer running Windows 8 with the Hyper-V feature enabled