Problems with virtual Hyper-V Client / Switch

We have the following problem by a customer:

There are Windows 7 Clients connecting to a share located on a virtual Windows 7 who is running on a physical Windows Server 2012 R2 with Hyper-V.
Sometimes (at least once per week), the connection from the clients (Windows 7 64-bit) to this share is lost and its not possible to connect until the physical Server is rebooted.
There are no Errors in the EventLogs on the physical Server and virtual Windows 7.
I have tried to rearrange the Virtual Switch, but did not resolve the problem.
Any similar issues from other Servers (more than five) with same components were until now not detected.

HP ProLiant ML310e 3.1/1220v3 G8
1x 3.1GHz Quad-Core CPU, 1x4GB PC3-12800E RAM, 4xLarge Form Factor Diskspaces, 1x Power Supply 350W, P222 RAID Controller

Hyper-V v2

Physical Server: Windows Server 2012 R2 Standard (German)
Virtual Win7: Windows 7 Professional 64-bit
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.


I am suspecting NIC driver issues on Windows 7 virtual machine, or physicals NIC's problems. Can you run some tests from some physical server, or from the switch?
Philip ElderTechnical Architect - HA/Compute/StorageCommented:
Broadcom NICs? Disable Virtual Machine Queueing (VMQ) on _all_ physical ports.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
SirAskALotAuthor Commented:

Thank you for the responses.

We have moved the shared data, located on the virtual Windows 7 to a physical (new) PC with Windows 7.

Yesterday, the problem has occured again.
The Clients could not connect to the share anymore. If trying to connect, Username and Password is required.
The Username / Password could not be accepted, because Active Directory not reachable.
So it had lost connection (only to) the the physical server (which is also the Domain Controller, they have only one).
The physical Server was running, but had no connection to the Internet. After rebooting the Server,
the share was accessible from any Client without problems.

After a view in the EventLog, i have seen that there are some warnings:

- Event ID 1014, DNS could not resolve a Name ***
- Event ID 12, Time Server not configured properly

What i have done on the physical Server after the problem occured:

- disabled IPv6
- configured a time server for the domain
- cleared the local DNS cache
- full system virusscan (no virus found)
- reboot firewall

If the problem occurs again, i will disable the VMQ on the physical NIC's and upgrade the NIC driver if possible.

@Philip Elder:
Yes they are Broadcom NIC's with VMQ enabled.
Acronis True Image 2019 just released!

Create a reliable backup. Make sure you always have dependable copies of your data so you can restore your entire system or individual files.

Philip ElderTechnical Architect - HA/Compute/StorageCommented:
I suggest _not_ waiting. It's a known issue with Broadcom enabling VMQ on Gigabit ports when the spec calls for it to be disabled. Things get muddled in the network stack as a result of it being enabled.
SirAskALotAuthor Commented:
Since i did the system changes listed above, the problem did not occured again. Anyway i updated the NIC driver and disabled VMQ.
I will observe the situation and give a feedback.
Philip ElderTechnical Architect - HA/Compute/StorageCommented:
I suggest enabling the firewall again. Make sure logging is enabled and pop-ups are enabled for new outbound service requests.

Enable IPv6 as that is used for internal communications in Windows Server.

VMQ is a known problem on Broadcom Gigabit NICs.
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.