Hyper-V web servers losing internet connection

Question

Hi,

I'm having issues with multiple hyper-v web servers since yesterday. We currently have hyper-v hosts in a failover cluster, all running virtual machines for different companies. Usually they have a DC, RDS, SQL and a WEB server, running Windows Server 2012 or 2016. Yesterday I've noticed on host4, the web servers (only on host4 and only the web servers) started to lose their internet connection one by one. Problematic VMs could not be reached by RDP connection but I've been able to log on to them from Hyper-v manager . The situation was the same on all the problematic VMs:

1. Internet connection lost
2. Can't even ping the default gateway
3. Happened on both 2012 and 2016 servers
4. All of them were on their own public network
5. All of them had fix ip addresses
6. No settings have been changed in the past 1 month on any of the affected VMs
7. All affected VMs were on host4
8. Live-migrating problematic VMs to another host solved the problem instantly

Since moving VMs to another host fixed the problem, I started to look for reasons on host4. No errors in the event logs whatsoever. Host4 has sufficient resources, when the issue happened it's volume had 69GB of free disk space out 3TB. It seems like there should be more free disk space but I don't see any reason for this to cause the issue since 2 other hosts have a similar amount of free space.

Do you have any suggestions on where to look for roots of this issue or how to fix it? It's the first time it happened and we've been running these hosts for many years now.

Answer 1

Hi，
Do you mean only web servers on host4 lose internet connection? And those problematic VMs cannot access the Internet and could not be reached by RDP connection. If there’s any misunderstanding, please feel free to feedback.

1. Please check if the host4 can ping other hosts.
2. Please check if the network NIC driver on host4 is updated to latest, if not, please update the NIC driver.
3. Please try to disable VMQ and TCP offloading on the NIC, check if it could help:
   (Disable TCP offloading which would cause network delays and intermittent failures)
   Open CMD as administrator and run the following command:
   Netsh int tcp set global chimney=disabled
   Netsh int tcp set global netdma=disabled
   Netsh int tcp set global autotuninglevel=disabled
   netsh interface teredo set state disabled
   netsh int ipv4 set global taskoffload=disabled
   Open powershell and run the following command to disable VMQ:
   Set-NetAdapterVmq -Name "NIC 1" -Enabled $False
4. Besides, please check if there's any network throttling configure on host4, if yes, please try to disable the throttling.

Thanks for your time!
Best Regards,
Mico Mi

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Answer 2

There might be a misunderstanding so let me explain it a little further. There are other kinds of VMs on Host4, not only web servers. But only the web servers are losing internet connection and only on host4. The host itself and the other VMs (also Windwos Servers but not web servers) on it are not facing any kind of network issues. If there was something wrong with the settings you've mentioned, I think all the VMs on host4 would lose internet connection. But only web servers are losing it.

There is one significant difference between the web servers and all the other servers on host4: Web servers are using a public network. All other servers are in domain networks (1 domain network per customer company).