I was recently asked about the Microsoft HyperV 2012 vSwitch and its basic operations.  So I thought I’d share that info.  Windows 2012 R2 server vSwitch has some significant capabilities and features that are warranted in virtualization.  But before we get too deep lets gets an overview.

One to One mapping of VM vNICs to pNIC

A virtual switch came about to allow sharing of hardware resources with virtual resources.  Originally, one would add one or more physical network interface card (pNIC) for each Virtual Machine (VM) they created allowing the VM to access the external network.  The image above shows a one to one mapping and all traffic between VMs has to cross the Network Switch.

Four to One mapping of VM vNICs to a pNIC

Early in virtualization there was a one to one ratio of vNIC to pNIC and no concept of a virtual switch.  The need better utilize physical Server Input/Output (IO), created the virtualization of the resources.  One of these resources in question being how does a virtual network interface card (vNIC) access the outside world via a shared pNIC.  The vSwitch is a software construct added to virtualization software to allow a single pNIC to be used by multiple vNICs across multiple VMs.  The image above shows the addition of a virtual switch which allows the VMs to exchange data between each other without ever leaving the server.

Six to Four mapping of VM vNICs to pNICs

The above image shows a realistic solution with multiple VMs (six in the example)  using 4 pNICs which can be setup in NIC team.