Friday, September 2, 2011

"netvsc" error with Hyper-V guest

We have many clients with Server 2008 running Hyper-V to virtualize the live servers. Virtualization has provided many benefits to our clients. (Reduced power consumption, increased uptime, added redundancy, server consolidation, hardware replacement for old servers while keeping the old server system OS, and much more)

As always when using technology as a solution, you are increasing the complexity. Thus along with the benefits come some increased risks & support.

A few times now we have seen a Server 2003 child machine completely stop communicating over the network. The Virtual Machine looks fine from Hyper-V Manager, but nothing can communicate to or from the child server.

The error looks like this:

Event Type:       Information
Event Source:     netvsc
Event Category:  None
Event ID:            4
Date:                 9/2/2011
Time:                3:49:53 PM
User:                 N/A
Computer:        SERVER10

The miniport ‘Microsoft Virtual Machine Bus Network Adapter' reset.

Once this happens, it's as if the network cable was disconnected from the Server 2003 Virtual Machine.  Obviously this causes a complete network shutdown for anyone using this server.


After much diagnostics, I found this to be related to the virtual machine network interface on the child server. Microsoft confirms a glitch with the 'Microsoft Virtual Machine Bus Network Adapter'

Driver Version: 6.1.7600.16385  
(This also represents the version of Integrated Services) 

 The FIX:

Microsoft has released an on demand (voluntary) hotfix related to this issue.
MS Article: KB981836

You must install the hotfix on the HOST SERVER (in my case Server 2008 R2 64bit w/ Hyper-V)

NOTE: This is not a patch that should be auto-installed. Only install this patch if a server is experiencing these exact symptoms explained in the KB article.  As of writing this blog, Microsoft requires you to 'request' the hotfix, its not auto-downloadable.

After installing the hotfix, you must update the Integrated Services on the 2003 Server VM.  This is what actually updates the Network Interface Drivers on the Child Server.

After the install, the VM Network Interface should be updated.
Driver Version: 6.1.7600.20683

In my case, I first create a snapshot of the child VM. After I install the hotfix on the HOST, I shutdown the child VM, then restarted the HOST server.

Once all goes well and you confirm the Driver Version is updated, shutdown your VM, delete the snapshot, then wait until it merges. Startup the VM and all should be well.

I also noticed that the HOST and Child servers seamed more responsive. I have yet to see the relation, but I do notice an improvement.

PLEASE NOTE: This should be performed by an experienced Server Administrator. This is NOT for the faint at heart.

Happy Clicking!

Nathan DeSutter
IT Consultant

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