Query on the 'Allow management operating system to share this network adapter' setting?

Question

I have a Hyper-V R2 Test box with 2 NICs. The setting 'Allow management operating system to share this network adapter' was enabled by default on the virtual network that was created as part of adding the Hyper-V role. I configured the virtual network to use the 2nd physical NIC on the box that will be dedicated for VM traffic.
I know that best practise recommends isolating the traffic for host management, and virtual machines between different NICs if possible.
Interestingly, when i unchecked the 'Allow management operating system to share this network adapter' checkbox, one my of my NICs (the one configured for VM traffic) immediately disappears from view in the list of network adapters. At the same time, wiping the static TCP/IP config I have applied to the NIC. Only the virtual switch and management connections remain visible. If i re-enable the above setting, the missing network adapter re-appears but with its previous statically set config wiped.
Q1 Is this expected behaviour?
Q2 In Hyper-V version 1.0, this setting doesn't exist. As such, does that mean the operating system would share the network adapter by default and cannot be disabled from doing so? I assume this is the case, as all of the network adapters are present/visible on the same server, and in the absence of this setting.
TIA for any advice
Mark

Answer 1

It is not that things are hidden - in fact part of the confusion is that too much is shown - it is that they are moved.
Lets go back to the beginning (I am going to describe R2):
If you have a host with two nics and zero External networks - in Network Connections you will see two interfaces.
Go into the Virtual Network Manager and create an External Virtual Network and bind it to NIC 2 - do not select the option for the management OS to share the network.
If you look at Network connections you still see two interfaces, but NIC 2 is now bound to the virtual network protocol - it is dedicated to being a port of the External Network.
This is what happens when you attach a physical NIC to an External Network - it becomes an extension of the External Network - the hypervisor owns it - the management OS does not.
Now - modify the External Virtual Network and turn on the option to share with the management OS.
If you look at Network Connections you will see a new (third) interface.
kThis new interface is a soft interface tht is only exposed to the management OS by the hypervisor - it is a virtual NIC that is attached to the External Network - thus allowing the management OS to share the physical NIC 2 with all the other 'domains'.
In the hypervisor language a 'domain' is a generic way to describe a system managed by the hypervisor - the parent (managemetn os) is domain 0 (dom0) and any VMs are domain 1 through n.  Therefore the management OS doe snot own the hardware, the hypervisor does - the management OS just handles managing the VMs and making sure they all play well with each other as well as creation and description, and managing networking and storage.   But it is really a special VM.
Brian Ehlert
(hopefully you have found this useful)