Each computer system needs at least one L2
NIC (Ethernet card) for communication. Therefore,
each physical system has at least one physical
NIC. However, if we run multiple VMs on
the system, each VM needs its own virtual NIC.
As shown in Fig. 1, one way to solve this problem
is for the “hypervisor” software that provides
processor virtualization also implements as
many virtual NICs (vNICs) as there are VMs.
These vNICs are interconnected via a virtual
switch (vSwitch) which is connected to the physical
NIC (pNIC). Multiple pNICs are connected
to a physical switch (pSwitch). We use this notation
of using p-prefix for physical and v-prefix
for virtual objects. In the figures, virtual objects
are shown by dotted lines, while physical objects
are shown by solid lines.