Windows 10: Slow download speed after creating Hyper-V External Virtual Switch

Hello.
After buying a new PC (its specs are on my profile), enabling Hyper-V and creating a new External Virtual Switch, I notice that the download speed drops dramatically. My internet conneciton is 1Gbps down and 200Mbps up.

Without External Virtual Switch:

• Speedtest (I get 944 Mbps download, and 214 Mbps upload) --> Speedtest.net by Ookla - My Results
• CPU usage while on Speedtest (no core is maxed out):

• Iperf with a host on the same LAN (upload 911Mbps, download 777Mbps):

• Lan Speed test (746 Mbps upload and 716 Mbps download):

With External Virtual Switch:

• Speedtest result (I get 378 Mbps download and 212 Mbps upload) --> Speedtest.net by Ookla - My Results

• CPU usage while on Speedtest (notice the first core is fully maxed out):

• Lan Speed Test (742 Mbps upload and 596Mbps download):

• Iperf with a host on the same LAN (upload 861 Mbps, download 583 Mbps):

• CPU usage while on Iperf (download) - Notice, once again, Core 1 fully maxed out​:

Conclusion

When the External Virtual Switch is enabled, I assume the download speed is lower due to the fact one CPU core is being maxed out, my question is why? Why isn't the load spread throughout the cores?
Is anyone experiencing a similar issue?

Regards.

:)

 

Hyper V: How to install guest operating OS?

Internet? Examples:

How to Create and Run Virtual Machines With Hyper-V

Create a virtual switch for Hyper-V virtual machines

 

Hyper-V virtual switch causes slow download speeds

I updated to Windows 10 Pro Fall Edition and it destroyed my virtual network. It removed my previous external virtual switch and replaced it with "Default Switch," and would not allow me to create a new Virtual Switch.

So I did what any sane person would do, and I wiped the entire machine and reinstalled Windows 10 Pro. I ran all the updates, and finally, it let me create the External Virtual Switch.

Except now it tanks my Host's download speed to 1 mb/s on an 800 mb/s line. When I remove the virtual switch, my download speed is restored.

This type of regression is not good. There are so many bugs in Windows 10 Fall edition that it should be seen as a huge failure. The performance of the machine in general is terrible. It lags and has issues with usb devices for some reason. This is a
clean install mind you. The simple fact that an update would even modify Virtual Settings in Hyper-v is abysmal, and now I cannot work because I can't connect to the internet with a reasonable speed if I choose to use VMs.

 

I have the exact same problem.
Any help would be appreciated.

 

Have you set the number of cores to 8 in hyer-v settings (virtual processor). No idea otherwise.

 

As of 1709 a Default Switch is created so you may not need an external switch.

Hyper-V virtual machine gallery and networking improvements | Virtualization Blog

You could try that instead (upgrade from 1703 to 1709 and delete external switch) - I don't see this issue on 1709 but then my connection is perhaps too slow (100 Mbps up/down).

 

Hello cereberus.
I was not clear in my first post. The slow download speed is not a problem of a virtualized OS, but the Windows original installation. The speed drops as soon as I enable the External Virtual Switch.

Hello lx07, I already have the 1709, but form what I've read so far, the thing with the Default switch is it used NAT, and I want my VM's to have access to my internal network.

Regards.

 

That is true.

There are a couple of suggestions here if you didn't see it already - either disable VMQ on the NIC or make sure RSS Base processor number is set to 0.

server 2012 hyper-v vSwitch performance is terrible

 

Hello lx07, my NIC does not support VMQ, even using powershell :-(

Regards.

 

I had the same problem and updating my network adapter drivers (in Device Manager) fixed my problem.

I just installed Windows 10 Pro on a Dell M6800 in Dec 2017, so I thought that all of my drivers were up to date, apparently they were not.

 

I've been experiencing the same thing lately. I just deleted ALL of my Hyper-V switches on this PC and I'll report back in if it results in improved Internet performance. So far, it already seems like a noticeable improvement.
--Ed--

 

I had a similar issue (I was not so thorough as to check all the resource usage graphs though!). In my case, the Hyper-V host (Win 10 Pro) experienced slow networking on downloads only (uploads were just fine), after creating an External Hyper-V virtual switch. Trashing the Hyper-V switch reliably restored download performance.

My physical adapter is an 'Intel(R) Ethernet Connection (2) I219-V #2'.

At my wit's end, chasing down driver updates, fussing with RSS paramters (clearly, it was a 'receive side' problem), stressing over absent 'VMQ' attributes allegedly present on some adapters (but not mine) as directed in mindless ways by people on the internet who don't know how to read ....
... I finally wondered if one of the protocols bound to the Hyper-V switch was interfering with it. Recall, that when Hyper-V sets up an external switch, it automatically (and blindly) migrates almost all the protocols bound to that NIC, to the new virtual NIC.

Spotting 'Intel(R) Technology Access Filter Driver' enabled, I reasoned that it may not apply to a Hyper-V virtual NIC, and turned it off.
Success! Full download speed returned!

 

"I had better educate myself about what this driver actually does", I thought to myself. Well, if you choose that route, I hope you have better luck than me. This creepy page was the best information I could find about it: Intel Management Engine software now includes an NDIS filter driver

Cynically, one is tempted to feel that Intel needed a quick & dirty way to help out a US intel agency hit a target, and wrote a handy little app which snuck in via the Management Engine software. That would explain both the denials at Issue with Intel Technology Access Driver |Intel Communities and the current un-informative and defunct product page at Downloads for Intel® Technology Access

 

So I'm wondering if anyone has an email address where I can invoice Intel for the lost time (at least 6 hours) chasing down the matter? Or maybe the NSA has a 'Incidental Victims of Compelled Technology Provider Interventions Fund' I could claim against? (I guess, complicated by not being a US citizen ...)

*Rolleyes