Protected Network
While the operating system and applications within virtual machines perform certain
tasks, the usefulness of those tasks is generally being able to communicate with
services via the network. If the network is unavailable on the Hyper-V host that the
virtual machine uses, traditionally clustering would take no action, which has been a
huge weakness. As far as clustering is aware, the virtual machine is still fine; it’s
running with no problems. Windows Server 2012 R2 introduced the concept of a
protected network to solve this final gap in high availability of virtual machines and
their connectivity.
The Protected Network setting allows specific virtual network adapters to be
configured as protected, as shown in Figure 7.11, via the Settings option of a virtual
machine and the Advanced Features options of the specific network adapter. If the
Hyper-V host loses network connectivity that the virtual machine network adapters
configured as a protected network are using, the virtual machines will be live-migrated
to another host in the cluster that does have network connectivity for that network.
This does require that the Hyper-V host still have network connectivity between the
Hyper-V hosts to allow Live Migration, but typically clusters will use different
networks for virtual machine connectivity than those used for Live Migration
purposes, which means Live Migration should still be possible.