Requirements to use Network Virtualization

Q. What is required to use Network Virtualization with Hyper-V?

A. Network Virtualization was introduced in Windows Server 2012 and provides a number of key capabilities including:

  • Complete isolation between different virtual networks
  • Abstraction of IP scheme used in the virtual network from the physical network infrastructure enabling virtual networks to use IP schemes incompatible with the physical network fabric and also enable virtual subnets to span physical locations. Different virtual networks can use the same IP scheme without fear of clashing
  • Windows Server 2012 R2 adds a built-in gateway which enables the connectivity of virtual networks to other networks using forwarding (if the IP scheme uses in the virtual network is compatible with the physical network), NAT (if IP scheme not compatible) and site-to-site
  • Purely software-defined removing the need to maintain often complex VLAN configurations and network hardware limitations

To use Network Virtualization a number of requirements exist:

  • Require Hyper-V 2012 or above (2012 R2 preferred)
  • System Center Virtual Machine Manager 2012 SP1 or above (2012 R2 preferred and requried if 2012 R2 Hyper-V)
  • Virtual switches on Hyper-V hosts must be created through SCVMM as logical switches
  • A logical network must be created which is enabled for network virtualization use. This logical network needs to have valid network configuration and IP pool which is used to allocated IP addresses to the Hyper-V hosts that are participating in hosting VMs in virtual networks (the Provider Addresses PA)
  • Create a VM Network that is configured to use network virtualization and has subnets added to it

With all of these requirements in place you can leverage network virtualization. Note that technically network virtualization is possible without SCVMM it is very complex and combersome. There are three planes to network virtualization:

  • Data - The actual communication between hosts which is a feature of Windows
  • Control - Exchange of policy and routing for the traffic between VMs in a virtual network. This is a combination of SCVMM and Windows Server. Consider if a VM is migrated. All Hyper-V hosts need to be updated to know the VM is now on a different Hyper-V host and traffic to that VM has to be routed accordingly
  • Management - This is performed by SCVMM

While the SCVMM duties could be performed using PowerShell there would be a huge amount of orchestration required, especially related to the migration of VMs between hosts.

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