Windows 2012 hyperv guest missing network connection after restore from backup

I am testing restores of a small hyperv windows 2012 server with the typical one host, two guest os (dc and apps) setup. However the DC is not handling DHCP, or any other normal domain controller tasks (this is lab setup which is not fully implemented). All three OS's have static ips. The backup is performed on the host server. When I restore to a different computer the only place it falls down is that the hyperv guests don't have any connection to the network. The settings on the hyperv manager side look like they do on the original box, but inside the guests in network properties there is nothing listed in the adapter settings area. I've tried twice with the same results, both windows server backup and a third party backup product. Both original and restore pcs are workstations not server boxes; and they are not identical. What I'm attempting is so routine that I suspect the solution will be simple.

I have tried removing the virutual switch on the host, adding a new external virtual switch, removing the old virtual switch from the vms and adding the new switch to the vms, but it has not helped.

June 28th, 2015 4:08pm

Hiya,

Wouldn't this be expected behavior? - As the MAC address would change, thus the O/S is not able to recognize the NIC's as the same and then unable to do the mapping from backup.

I guess you will end up with ghost NIC's on your guests.

Could you please remove the NIC's from the guests machines and add new ones and connect these to the host and see if this resolves your issue.

I do think that this is host related, but guest related.

And I would expect the same thing to happen, if you restored a physical machine to new hardware.

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June 29th, 2015 3:45am

Hiya,

Wouldn't this be expected behavior? - As the MAC address would change, thus the O/S is not able to recognize the NIC's as the same and then unable to do the mapping from backup.

I guess you will end up with ghost NIC's on your guests.

Could you please remove the NIC's from the guests machines and add new ones and connect these to the host and see if this resolves your issue.

I do think that this is host related, but guest related.

And I would expect the same thing to happen, if you restored a physical machine to new hardware.

June 29th, 2015 7:40am

Hi Jesper

I can't speak to why the guests don't have network connections, else I probably would not have posted here <g>. I'm not an expert in this area. Your advice is probably correct but I am not sure and so far I still can't get it to work.

One thing I had not noticed before is that on the host the original nic was not active, and a new nic was instantiated. The new nic provides an network connection, but without the static IP the server can't take over the roles it had. I tried disabling the old nic (don't see a way to completely remove it) and setting the new nic to a static ip. That results in a fail. When I run the diagnostic, it enables DHCP, and the nic works, but has tossed the static ip again. I don't get that. Is the old nic still hanging on to the ip address it was assigned in the original server?

And, I have deleted and recreated the host's virtual switch, and the guest virtual switches and nics. They still don't have network connections. Is this issue related to the host nic's auto assigned ip address or something of that order?


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June 29th, 2015 11:40am

Hi rusticloud,

>>And, I have deleted and recreated the host's virtual switch, and the guest virtual switches and nics. They still don't have network connections.

Does it mean there is no NIC listed in "Network Connections" ?

There is nothing to do with host's virtual switch .

As a workaround I would suggest you to restore VM's files to get the VM's VHD file then create a new VM and attach that VHD file .

Best Regards,

Elton Ji

June 30th, 2015 12:34am

Yes in the guests there are no NICs listed.

You're suggesting that I let the restore set up the hyperv guests, then save the VHD file, and manually make new hyperv guests manually?

But, isn't there a 'normal' way in which hyperv guests can be restored from image?

And the host still has the issue where it insists on using an automatically assigned ip address; it won't take the static IP that it needs to have in order to stand in for the machine that was backed up.

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June 30th, 2015 12:39am

One issue is fixed. While I had the original server off, it still had the network cable connected. After I pulled the cable, I was able to assign the static ip address to the host adapter.

I may have made some progress with the hyperv networks too. In hypverv manager for the guest I set the virtual switch to 'not connected', and then back to the vswitch. Then in the vm I finally saw a network adapter show up. I had device manager show hidden devices and found two disabled hyperv nics; I uninstalled them. Still, the remaining hyper-v adapter is not assigned an ip address from my router - it uses an ip that is completely different, and no network or internet access as a result.

Anyone know how to fix that?
June 30th, 2015 7:14pm

What I eventually figured out via much experimentation is that since the nic in the 'restore to' pc was different from the 'backup' pc, after restore the network was not capable of running correction 'as is'. The old nic would restore as disabled, which means that the virtual switch that it enabled was also non-working.

Here is an outline of what I discovered in case it's useful for someone else down the road.

- Since the old nic is not available after restore, the nic in the 'restore to' pc will be instantiated with an automatically assigned ip address.
- The nic in the 'restore to' pc will not have Hyper-V Extensible Virtual Switch turned on.
- Since the nic in the 'restore to' pc is offine, the vswitch that depends on it will also be offline, and thus network will not be available to vms.

To get things working again:

- Stop any running vms
- Redirect the vswitch to the nic that is present the 'restore to' box; rename the vswitch.
- The existing vms will automatically pick up on the name change and will use the new settings.
- A new vswitch entry will be created in network connections.
- The physical nic will have Hyper-V Extensible Virtual Switch on and all other entries like tcp/ip turned off.
- The old vswitch will remain in the network connections console with 'unidentified network' until that that console is closed and reopened.
- start a vm and test.

In the end it's pretty straightforward; but I couldn't find a walk-through that explains what I experienced. Since I didn't understand the relationship between the virtual switch and the nic, it took some experimentation to get a handle on it.
  • Marked as answer by rusticloud 7 hours 12 minutes ago
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July 3rd, 2015 7:54pm

What I eventually figured out via much experimentation is that since the nic in the 'restore to' pc was different from the 'backup' pc, after restore the network was not capable of running correction 'as is'. The old nic would restore as disabled, which means that the virtual switch that it enabled was also non-working.

Here is an outline of what I discovered in case it's useful for someone else down the road.

- Since the old nic is not available after restore, the nic in the 'restore to' pc will be instantiated with an automatically assigned ip address.
- The nic in the 'restore to' pc will not have Hyper-V Extensible Virtual Switch turned on.
- Since the nic in the 'restore to' pc is offine, the vswitch that depends on it will also be offline, and thus network will not be available to vms.

To get things working again:

- Stop any running vms
- Redirect the vswitch to the nic that is present the 'restore to' box; rename the vswitch.
- The existing vms will automatically pick up on the name change and will use the new settings.
- A new vswitch entry will be created in network connections.
- The physical nic will have Hyper-V Extensible Virtual Switch on and all other entries like tcp/ip turned off.
- The old vswitch will remain in the network connections console with 'unidentified network' until that that console is closed and reopened.
- start a vm and test.

In the end it's pretty straightforward; but I couldn't find a walk-through that explains what I experienced. Since I didn't understand the relationship between the virtual switch and the nic, it took some experimentation to get a handle on it.
  • Marked as answer by rusticloud Friday, July 03, 2015 11:48 PM
July 3rd, 2015 11:48pm

Thanks for updating the post for others to find! :)

Glad it worked out!

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July 6th, 2015 2:37am

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