Virtual Switch Fundamentals
A typical server has one or more network adapters that are configured with an IPv4
and IPv6 address, either statically or dynamically, using services such as Dynamic
Host Configuration Protocol (DHCP). The server may be part of a VLAN to provide
isolation and control of broadcast traffic. It may require different network connections
to connect to different networks, such as a separate, nonrouted network for cluster
communications between servers in a failover cluster, a separate network for iSCSI
traffic, a separate management network, and so on. With virtualization, the
requirements for network connectivity are just as important as they are for a physical
server. However, additional options are available because multiple server instances
exist on a single physical asset. Moreover, in some cases, they need to communicate
only with each other and not externally to the virtualization host.
Three Types of Virtual Switches
Virtual machines have numerous virtualized resources. One type is the virtual
network adapter (as discussed in the previous chapter, two types of network adapters
are available for a generation 1 virtual machine, but their connectivity options are the
same). One or more virtual network adapters are added to a virtual machine, and then
each virtual adapter is attached to a virtual switch that was created at the Hyper-V
host level. A Hyper-V host can have many virtual switches created. Three types of
virtual switches are available: external, internal, and private, as shown in Figure 3.1.
Figure 3.1 The three types of virtual switches available in Hyper-V
EXTERNAL VIRTUAL NETWORKS
External virtual networks are bound to a physical network card in the host. Virtual
machines have access to this physical network via the physical NIC, which is linked to