Hyper-V: Why is networking reset in my VM when I copy a VHD?

Hyper-V: Why is networking reset in my VM when I copy a VHD? | Windows 2008 Security

Wed, 23 Jul 2008 16:41:05 GMT

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re: Hyper-V: Why is networking reset in my VM when I copy a VHD?

c8to — Fri, 25 Jul 2008 22:21:50 GMT

heh...just encountered this today.

i migrated all the virtual machines using import export and all was fine.

the first one i imported in a directory called import, and then after i knew how it worked, i imported them to a directory called virtualMachine.

later on, to be consistent, i moved that first one into the directory with the others, but of course you can't reimport a second time so all was doomed.

a critical domain server no less.

luckily i figured out what happened, removed the old network card and reinstituted the settings. i had all the information on hand but it would be a shame if you lost those ip settings, as in the case you described with something more complicated like a router!

re: Hyper-V: Why is networking reset in my VM when I copy a VHD?

c8to — Fri, 25 Jul 2008 22:26:14 GMT

one further questions which came up with regards to networking, is when you have two network adapters, one dedicated for remote access and the second configured for a virtual switch, the system log can report an error that there are two network adapters sharing the one machine name (obviously)

is it best practise to ignore this error, or to disable the created local area connection on the parent (really first guest OS on top of Hyper v) and just have the one real connection.

also it would be great if your networking overview post on another page included how to setup the IP addresses correctly as best practise (for example comment on this nbtstat issue and dual gateway warnings when you do have two or more adapters)

Lazy Monday… Link’s to other great blog posts.

Taylor Brown's Blog — Mon, 28 Jul 2008 20:08:04 GMT

I've been a little light on content the last few weeks (the post RTM hangover is stating to fade finally)... 

re: Hyper-V: Why is networking reset in my VM when I copy a VHD?

Tore Lervik — Thu, 07 Aug 2008 17:19:28 GMT

Having a VM with a external network connection called "Internet".

Both servers have a network named "Internet" that is external and "test" that is internal.

When exporting this vm and then import it on another server the external network is now set to "Not connected" as the importer failed to find the network.

But if i do the same thing with a VM where the "test" network is used, it will use the "test" network when it's importet.

Why is this?

re: Hyper-V: Why is networking reset in my VM when I copy a VHD?

jhoward — Thu, 07 Aug 2008 20:55:07 GMT

c8to - you should either create through WMI a "dedicated" network for the VMs (preferred), or remove the bindings from the virtual NIC in the parent partition created when the external network switch was created, or even disable that virtual NIC

Thanks,

John.

re: Hyper-V: Why is networking reset in my VM when I copy a VHD?

Chuck vdL — Tue, 19 Aug 2008 20:35:35 GMT

Great tip.. just ran into this with a Vista VM and wanted to get rid of the old emulated NIC..

BTW the KB mentioned is for earlier OS's, and doesn't know about UAC, and thus the steps it give won't work for vista or server2008.

Fortunately the solution is easy (you mentioned it pretty much in passing, so it's could be easy to miss).. for those steps to work you HAVE to use an 'elevated' (right click, run as administrator) command prompt to set the ENV variable.. otherwise when you run devmgmt it will get it's own pristine copy of the environment and won't see the env variable you just SET a moment before.

re: Hyper-V: Why is networking reset in my VM when I copy a VHD?

Bill — Wed, 24 Sep 2008 01:00:25 GMT

John, is the default location \programdata\microsoft\windows\hyper-v\virtual machines hardcoded? Or is it something that could be obtained programmatically using a WMI call for example. I mean similar to "ExternalDataRoot" which is part of the Msvm_VirtualSystemGlobalSettingData. If it is hardcoded, does it use the %ProgramData% environment variable? I noticed that when I create a new Vm in my own folder, a symlink is created in the default folder pointing to the XML configuration file that is created in my own folder. I was wondering if it is possible to determine the default folder programmatically or should I just use \programdata\microsoft\windows\hyper-v\virtual machines or %programdata%\microsoft\windows\hyper-v\virtual machines? What's the most reliable way of determining the location of this system folder? Thanks.

re: Hyper-V: Why is networking reset in my VM when I copy a VHD?

jhoward — Wed, 24 Sep 2008 23:04:15 GMT

Bill -

Msvm_VirtualSystemManagementServiceSettingData.DefaultExternalDataRoot. A symbolic link will always be created in the default location you specifid, but the full VM config file will be created, by default, in the location specified in this property.

Cheers,

John.

re: Hyper-V: Why is networking reset in my VM when I copy a VHD?

Anagha — Tue, 03 Mar 2009 02:05:01 GMT

John,

Is there a way to retrieve ChannelInstanceGuid of SCSI controller of a VM through WMI?

re: Hyper-V: Why is networking reset in my VM when I copy a VHD?

Shiva — Tue, 14 Apr 2009 14:15:16 GMT

John,

You are GOD! This link helped a lot.