Solved Local Network Problems When Hyper-V is Enabled

hsehestedt · Feb 12, 2023

I've been struggling with something for at least a year and just wondering if others have run into this and have any solution.

The issue is that I have a constantly recurring network issue. Here is the scenario:

I have multiple desktop machines in one room. They are connected to my home network using Ethernet.

I also have a laptop that uses WiFi to connect to the home network.

If I remote desktop to my desktop computers from the laptop, everything works great including transferring files over that remote desktop connection. However, if I instead map a network drive to those desktops, I get some weird behavior. I can navigate through directories on the mapped drive just fine, but if I try to copy a file to the desktop systems, file explorer opens a progress window, but it will never make any forward progress. It just sits there forever without actually copying the file.

On the laptop, I have Hyper-V enabled. In Hyper-V I have a virtual switch that allows access to my local network and to the Internet by using the WiFi adapter. I have the option selected to share that WiFi connection with Windows management.

If I now uninstall Hyper-V, my network problems go away. So somehow, having Hyper-V enabled is causing these network issues, but for the life of me I have no idea why.

I should also note that with Hyper-V enabled, other network activity such as accessing the Internet, works just fine. It just seems to be mapping drives to other systems on the local network that is affected.

Anyone have thoughts on this?

Digital Life · Feb 12, 2023

Look in the Virtual Switch Manager and click on your External switch, Then check that " Allow management OS to share this network adapter " is checked

hsehestedt · Feb 12, 2023

Thanks for the suggestion, but as I noted in my original post, I already have that option selected. Also, if it was not selected, I woudn't have partial connectivity as I noted.

In the meantime, I've done further testing. If I remove the External Network connection, then the connectivity from the physical machine wrks just fine, so it is definitely some sort of issue related to enabling the external network connection in Hyper-V.

hsehestedt · Feb 13, 2023

Okay, I was up all night trying to figure this out and I got it, so I'm going to post the solution to my own problem here, just in case anyone stumbles on this looking to resolve the same issue.

The solution was simple (once I knew what it was): Go into the settings for the WiFi adapter and disable "Packet Coalescing".

Summary:

Symptom: SOME network connectivity will not function properly over WiFi. Access to the Internet and Remote Desktop to other systems on the local LAN are not affected, however, if you try to copy data to shares on other computers, that will fail.

Conditions: This issue can happen if you have Hyper-V enabled on your system AND you have created a Virtual Switch of the type "External". As a test to verify that this is the cause of your network problems, simply temporarily remove the External Network type from within Hyper-V Manager > Virtual Switch Manager. If the problem goes away, then this is the issue.

Resolution: If you removed the External Network above for testing, feel free to re-create that network at any time. In the meantime, go into your WiFi adapter settings and DISABLE the setting called "Packet Coalescing".

What WiFi adapters are affected by this issue?

I have no idea. However, I do know that not all adapters seem to be affected. I have a laptop with an Intel AX210 WiFi adapter that IS affected by this issue. However, I have another system that has an older Intel AC 7265 and even with Packet Coalescing enabled on that adapter, the issue is not present on that system.

NavyLCDR · Feb 13, 2023

Thank you for that! I just turned off packet coalescing, just in case

cereberus · Feb 13, 2023

See post #2 in link below I made a while back.

A virtual switch slows Host's connection to other physical devices

I'm running Hyper-V on Windows 11 Pro, General Availability Channel, build 22000.527. The symptoms are almost identical to those @Kari described in this Win10 Guru article from 4 years ago. Using any external switches other than the Default switch in Hyper-V ... file transfer between the...

www.elevenforum.com

Just fixing coalescing may help downloads but not always uploads. The link above covers both.

Also see older Windows 10 post

Very slow up/download speeds with HyperV external switch setup - Windows 10 Help Forums

A long standing issue for many Hyper-V users is when you set up an external wifi switch in Hyper-V, it kills the download and/or upload speeds. On my ASUS with an Intel NIC, my uploads and downloads are only 2% of normal speeds making internet virtually u

www.tenforums.com

hsehestedt · Feb 19, 2023

@cereberus, apologies for the slow response. I completely missed your post. I only noticed it when I came back here to post an update.

My update was going to be to note the fact that the problem returned for me. After more experimenting I noticed that disabling packet coalescing was only a temporary solution. It actually turns out that altering any setting that causes a reset of the WiFi adapter will cause everything to work temporarily.

However, your post about disabling Large Send Offload Version 2 (IPv4) and Large Send Offload Version 2 (IPv6) caught me by surprise. I tried that and now all is well even several reboots later.

So for anyone following this thread, here is a full summary:

Symptom

Note that this problem happens ONLY if I go into Hyper-V Manager > Virtual Switch Manager, and I create an "External" virtual switch. The virtual switch does NOT need to be assigned to any VM, in fact, I don't need to even have any VMs created on the system. Just the mere existence of the External virtual switch is enough.

With this virtual switch present, if I connect to a share on another computer, I can successfully copy files from that share to the laptop. I can also copy small files to the share. By small, I mean files of about 2 MB and smaller. If I attempt to copy anything larger, say 10 MB, the copy will start, then it sits there for several minutes, then it copies maybe another half a MB, pauses several minutes, then copies a little bit more, etc. To copy a 10 MB file may take 5+ minutes.

Here is where it gets even stranger: If I go to the computer with the share and I remote desktop into the laptop, and then try the file copy again, it will work perfectly normally.

In addition, if I do anything on the laptop that resets the WiFi adapter, for example, if I change a setting on the WiFi adapter, then the copy will suddenly resume and run to completion. As an example, say I start a large file copy of 10 GB. The copy pauses (hangs) as I described above. Now I go into the WiFi settings and alter some setting. That causes the WiFi adapter to reset. Bang - the copy will immediately resume and run without any further pauses. However, this working condition is only temporary.

If I remove the Hyper-V external switch, then this problem will never ever happen.

Solution

The solution is to implement the settings noted by cereberus. To be very specific, do the following:

Go to Control Panel > Network and Internet > Network Connection. Right-click on the Network Bridge and select Properties. Select the virtual Ethernet adapter and then click on Configure. Go to the Advanced tab. Disable both Large Send Offload Version 2 (IPv4) and Large Send Offload Version 2 (IPv6).

cereberus · Feb 19, 2023

hsehestedt said:
@cereberus, apologies for the slow response. I completely missed your post. I only noticed it when I came back here to post an update.

My update was going to be to note the fact that the problem returned for me. After more experimenting I noticed that disabling packet coalescing was only a temporary solution. It actually turns out that altering any setting that causes a reset of the WiFi adapter will cause everything to work temporarily.

However, your post about disabling Large Send Offload Version 2 (IPv4) and Large Send Offload Version 2 (IPv6) caught me by surprise. I tried that and now all is well even several reboots later.

So for anyone following this thread, here is a full summary:

Symptom

Note that this problem happens ONLY if I go into Hyper-V Manager > Virtual Switch Manager, and I create an "External" virtual switch. The virtual switch does NOT need to be assigned to any VM, in fact, I don't need to even have any VMs created on the system. Just the mere existence of the External virtual switch is enough.

With this virtual switch present, if I connect to a share on another computer, I can successfully copy files from that share to the laptop. I can also copy small files to the share. By small, I mean files of about 2 MB and smaller. If I attempt to copy anything larger, say 10 MB, the copy will start, then it sits there for several minutes, then it copies maybe another half a MB, pauses several minutes, then copies a little bit more, etc. To copy a 10 MB file may take 5+ minutes.

Here is where it gets even stranger: If I go to the computer with the share and I remote desktop into the laptop, and then try the file copy again, it will work perfectly normally.

In addition, if I do anything on the laptop that resets the WiFi adapter, for example, if I change a setting on the WiFi adapter, then the copy will suddenly resume and run to completion. As an example, say I start a large file copy of 10 GB. The copy pauses (hangs) as I described above. Now I go into the WiFi settings and alter some setting. That causes the WiFi adapter to reset. Bang - the copy will immediately resume and run without any further pauses. However, this working condition is only temporary.

If I remove the Hyper-V external switch, then this problem will never ever happen.

Solution

The solution is to implement the settings noted by cereberus. To be very specific, do the following:

Go to Control Panel > Network and Internet > Network Connection. Right-click on the Network Bridge and select Properties. Select the virtual Ethernet adapter and then click on Configure. Go to the Advanced tab. Disable both Large Send Offload Version 2 (IPv4) and Large Send Offload Version 2 (IPv6).

I recommend the coalescing steps as well. It varies but I needed both.

Its great to be able to declare "Been there, done that, got the T-shirt" on this subject LOL

Solved Local Network Problems When Hyper-V is Enabled

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