Windows 7 Guest Network dies

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I have a Windows 7 guest that was created on a KVM machine and imported to RHEV using virt-v2v.

 

On the KVM, the Win7 guest worked fine. After importing to RHEV, I can tranfer just a small amount of data (about 4K) and the network just shuts down.

I ran into this issue using a Cisco Blade system and using VM-FEX, and the problem turned out to be with Generic Receive Offload. Shutting gro off on the blade interfaces made the system work. Turning gro off on this server's interfaces did do anything.

I have tried both the RH virt io drivers as well as the realtek drivers. It doesn't seem to make a difference.

I have two interfaces, one connected to a rhevm, the other connected to a private vlan. It does not seem to make a difference which interface is used or if one or the other is disabled on the guest.

Is there anything specific I can look at to find out why my network does not work?

 

Thanx for any help you can give.

 

Frank

FC
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GS Expert Active Contributor 1269 points
19 July 2013 7:00 PM

I had a similar problem a couple years ago, where bulk transfers would knock my Windows VM offline. The problem was very irritating because I only had a limited time window and my bulk copy would usually run for several hours before blowing up.  The only recovery was to get on the VM console, disable and re-enable the NIC driver, and start over again.  

Turned out, there was a recent update to the virtio driver that cured my problem.  I was mad enough to chew neutronium after several miserable days, but also grateful to finally have a fix.  

Long-winded story, but maybe a good place to start is learning from my mistake.  Make sure you have the latest and greatest Virtio and/or Realtek driver.  

A characterizing question - when the network shuts down - just for this guest or globally for all guests?

And a troubleshooting step - when the problem shows up, what happens when you get on that Win 7 console and disable and re-enable the effected NIC driver?  

- Greg

FC Active Contributor 246 points
19 July 2013 8:52 PM

Well good news.

Although I am not sure what was changed, our network admin changed something on the firewall and or the switch to which it was connected and suddenly everything started working again. He says that it was a minor change that shouldn't have had that effect, but I am just glad it is working again. (This after repeated assertions that it could not be a network error.)

Greg, Thanks for your advice. Since this was the first guest, both on this host as well as on the private network, I couldn't tell if it was global or just one guest. If the problem returns, that is one of the first things I will test.

Again, thanks for the help.

GS Expert Active Contributor 1269 points
19 July 2013 9:35 PM

Ya know, just to be thorough - would you be able to persuade your Network Admin to temporarily back out the changes and see if the problem comes back?

- Greg

David Powles's picture Red Hat 25369 points
26 July 2013 7:55 AM

(Private) I'm featuring this topic. More great help provided by Greg Scott!

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