IP address is moved from virtual network adapter back to physical network adapter.

Joeri Michiels 1 Reputation point
2021-09-24T12:02:12.897+00:00

Hi,

We're using Windows Server 2019 to run Hyper-V that runs a virtual machine. When we initially created this virtual machine, we also created a virtual switch and assigned it to the VM, so that it would be able to connect to the network.
When creating this new virtual switch in Virtual Switch Manager we selected 'External Network' for the Connection Type.
When doing this it transfers the ip address configuration of the physical network adapter to the new virtual network switch.
All this works perfectly and the VM can reach the network when this setup is completed.

However for some time we have seen that on some of our Windows Servers the ip address was moved back from the virtual network adapter to the physical network adapter. Obviously at this point the virtual machine looses the connection to the network.

Since none of my colleagues confirmed that they have done this manual move, could it be that this can happen automatically ?
I've googled around but couldn't find a clue on this.
Do you know of any circumstances where this 'rollback' can happen automatically ?

Thanks for your ideas.

Best regards

Joeri

Hyper-V
Hyper-V
A Windows technology providing a hypervisor-based virtualization solution enabling customers to consolidate workloads onto a single server.
2,536 questions
0 comments

2 answers

Sort by: Most helpful
Most helpful Newest Oldest
  1. Dave Patrick 426.1K Reputation points MVP
    2021-09-24T12:42:53.823+00:00

    it transfers the ip address configuration of the physical network adapter to the new virtual network switch.

    vSwitches do not have ip addresses. It sounds like the properties of the vSwitch may have been altered. When you create a new external vSwitch the internet protocols are removed from the adapter and the Hyper-V Extensible Switch protocol is added turning that physical port into a multi-port virtual switch. I'd suggest deleting / recreating the vSwitch.

    --please don't forget to upvote and Accept as answer if the reply is helpful--

  2. Limitless Technology 39,351 Reputation points
    2021-09-27T16:40:12.897+00:00

    Hello @Joeri Michiels

    This happens because some DHCP Servers will assign IP based on MAC address, and the virtual adapter MAC is "invisible for the DHCP server".

    My recommendation would be:

    • Configure MAC spoofing in the VM seetings
    • disable VMQ , tcp/ip offload , RSS on that external virtual switch
    • Assign static IPs to each connection
    • restart Host and VMs

    Hope this helps with your query,

    -----------------

    --If the reply is helpful, please Upvote and Accept as answer--

    0 comments