Types of Guest Network Adapters
Two types of network adapters are available to a generation 1 virtual machine: legacy
(emulated Intel 21140-Based PCI Fast Ethernet) and synthetic. As discussed in
Chapter 2, “Virtual Machine Resource Fundamentals,” emulated hardware is never
desirable because of the decreased performance and higher overhead, which means
that the legacy network adapter is used for only two purposes in a generation 1 virtual
machine:
Running an operating system that does not have Hyper-V Integration Services
available and therefore cannot use the synthetic network adapter (this would mean
the operating system is also unsupported on Hyper-V)
Needing to boot the virtual machine over the network, known as PXE boot. If this
is the reason, then initially use a legacy network adapter, but after the operating
system is installed, switch to the synthetic network adapter for the improved
performance.Additionally, QoS and hardware-acceleration features are not available for legacy
network adapters, making the standard network adapter your default choice. Each
virtual machine can have up to eight network adapters (synthetic) and four legacy
network adapters.
Many options are available for a network adapter that are configured through the
virtual machine properties by selecting the network adapter (legacy network adapter
or network adapter).If there are multiple network adapters for a virtual machine, each
adapter has its own set of configurations. These configurations are divided into three
areas: core configurations, hardware acceleration (not available for legacy network
adapters), and advanced features, as shown in Figure 3.47. Figure 3.47 also shows
Device Manager running in the virtual machine whose properties are being displayed,
which shows the two network adapters. The Intel 21140-Based PCI Faster Ethernet
Adapter (Emulate) is the legacy network adapter, and the Microsoft Virtual Machine
Bus Network Adapter is the network adapter.