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Hyper-V External Switches killing Networking in Insider builds


I use Hyper-V a lot. All of my physical machines run the UK English x64 PRO edition of the latest Windows Insider build, along with other language versions of Windows 10 I regularly need (FIN, SWE & GER), with both of the latest official release and Insider builds also running on Hyper-V virtual machines.

Until Windows Insider Build 17704 everything worked perfectly. I was able to use my external switches both on host and virtual machines, with no networking issues whatsoever. File transfers operated at full speed without delays.

Build 17711 (released July 6) and now build 17713 (released a week later) have changed this. Now, if I have any external switches other than Hyper-V’s own Default switch enabled, networking is simply not impossible. Not only is the connection between the host and its virtual machines effectively lost, it also affects the host’s connection to other physical machines.

A picture is better than thousand words. Here, I have enabled a self-created external switch on this laptop. On another physical machine I can map and browse the laptop’s shares normally, but file transfer from or to laptop is so maddeningly slow that it in fact is useless even to try. Thus, for example, the file copy dialog shows nothing happening:

Checking Task Manager, I can see that network activity is occurring, but file transfer is so slow it would take a few weeks to transfer an ISO. Ouch!

Disabling all external switches except Default, file transfer between both physical and virtual machines is as it should be:

Indeed, the default switch in Hyper-V works without issues, allowing networking at full speed. But the reason I must create and use an additional external switch is because I am using the Windows Admin Center (WAC) to administer and manage all my physical and virtual machines. It’s simple: if a VM uses default switch, I cannot connect to it from WAC:

When I switch the virtual machine’s NIC to a “normal” external switch, I can use WAC to start it and connect using WAC Remote Desktop:

Using WAC Remote Desktop to connect to a VM. Click to open enlarged in a new tab.

However, this is almost useless now because the external switch makes file transfer and other networking tasks nearly impossible. In the current 17713 build, as well as in the previous 17711 build, I find myself constantly enabling an external switch to manage my virtual machines using WAC, then disabling that switch and using the Default switch to get any serious networking done. This is quite annoying.

Here’s a shortened version of the long preceding story: Using any external switches other than the Default switch in Hyper-V on a build 17711 or 17713 host, file transfer between the host and its virtual machines or the host and other physical computers becomes impossible. I for sure hope Microsoft fixes this in its next Insider builds.

Kari

P.S. For more information about WAC and how to use it to manage your Windows 10 workgroup computers and virtual machines, see the tutorial I wrote on Ten Forums: https://www.tenforums.com/tutorials/113966-windows-admin-center-centrally-manage-all-your-windows-10-pcs.html

Author: Kari Finn

A Windows Insider MVP, Kari started in computing in the mid 80’s writing code for VAX / VMS systems. Since then, he’s worked in a variety of IT positions. He specializes in Windows image capture, customization, repair and deployment as well as Hyper-V virtualization. Kari is a proud Team Member at number #1 Windows site TenForums.com.

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