placement logic will not allow Live Migration to hosts using a different logical switch.
If you have a scenario requiring different logical switches in the environment (for
example, if you require different extension configurations), then a Live Migration
would not be possible and may be a reason for those hosts not to use the logical
switch and instead perform the switch configuration directly on the Hyper-V hosts;
this type of switch is known as a standard switch. Standard switches are fully
supported within SCVMM, and their deployment and configuration occur via Hyper-V
Manager or SCVMM.
If you had an existing Hyper-V server with virtual switches defined that will be
standard switches in SCVMM, there was no way to convert them to logical switches
prior to SCVMM 2016. A new option in SCVMM 2016, however, allows a standard
switch to be converted to a logical switch. This conversion is facilitated through the
properties of the host in the Fabric workspace: Select the Virtual Switches tab, select
the standard switch, and then, at the bottom of the details, there is a button to convert
to a logical switch. Click the button, select a logical switch that is equivalent to the
connectivity, and the switch will be converted to a logical switch on the host.
It is also still possible to delete the standard switches and then re-create the switches
as logical switches via SCVMM. To delete the standard switches, you would need to
evacuate the host of virtual machines, which typically means that you have a cluster.
However, with Windows Server 2012 and above, you can also move virtual machines
with no downtime by using Shared Nothing Live Migration between any Hyper-V
hosts, provided that they have a 1Gbps network connection. Of course, none of this
should be required if you ensure that all configuration is done through SCVMM
initially after planning out the logical networks, logical switches, and all other
components before deploying Hyper-V hosts.
VM NETWORKS
While the logical network provides the modeling of the networks available in the
environment and the desired isolation, the goal for virtualization is to separate and
abstract these logical networks from the actual virtual machines. This abstraction is
achieved through the use of VM networks, which is another networking architectural
component in SCVMM. Through the use of VM networks, the virtual machines have
no idea of the underlying technology used by the logical networks—for example,
whether VLANs are used on the network fabric. Virtual machine virtual network
adapters can be connected to only a VM network. When Network Virtualization is
used, the customer address (CA) space is defined as part of the VM network, allowing
specific VM subnets to be created as needed within the VM network.
In some scenarios, the isolation provided by VM networks might not be required—for
example, when Direct Access to the infrastructure is required (such as if your SCVMM
server is running in a virtual machine) or when the network is used for cluster
communications. It is possible to create a no-isolation pass-through VM network that
directly passes communication through to the logical network. The VM network is