Hyper-V virtual machine upload speed unbelievably slow

Question

I have the weirdest problem I was hoping you could help me with. I've got a dedicated Server 2012R2 server with an Intel 82580 network adapter. It runs a couple of VMs in Hyper-V that are attached to an Internal virtual switch. This switch is then NATted to various IP addresses on the real interface of the server.

I've currently got two guests running, an Ubuntu guest and a Server 2008R2 guest. Both get really good download speed (90Mbps, about what the dedicated server gets) but the upload speed is really bad. The dedicated server has an upload speed of about 60Mbps, the 2008R2 VM gets about 5Mbit and the Linux VM gets a speed too low to measure, the test just reads 0.00Mbit.

Does anyone know what the issue could be here? I've tried disabling VMQ, disabling IPv4 checksum offloading and disabling IPsec task offloading, none of which made any difference what-so-ever.

what's the storage? I'd guess writing to the virtual disk is the bottleneck and not the actual bandwidth / network. — user16081-JoeT, Apr 17 '15 at 02:31

score 5 · Answer 1 · answered Apr 17 '15 at 08:56

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I appear to have solved the issue by disabling large send offloading in the guest operating systems. Disabling it on the host didn't help but disabling it on the guests solved the issue.

answered Apr 17 '15 at 08:56

Guzzlebot

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Thanks for the tip. I had a similar problem, and disabling large send offload resolved it. – Thomas Levesque Jan 23 '16 at 15:48
Solved the issue for me as well inside a Virtual Machine using Veertu 1.2 running W10 on a Mac. – Peheje Feb 01 '17 at 16:12
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Instead of disabling Large Send Offload in the VM, you can also disable it on the vEthernet interface that Hyper-V creates on the host OS (useful if you have multiple guests using the same virtual switch.) – Joe the Coder Oct 19 '18 at 19:08
I've been banging my head left and right for the past 3 days on this issue, and this finally fixed it! Brand new PC, Win 11 Pro, Hyper-V, and new Win 10 Pro on VM, copying files from host to VM was ungodly slow, now it's instant. You should mark your answer as accepted so that others may find it. – Jerry Dodge Feb 11 '23 at 17:16

score 2 · Answer 2 · answered Jun 09 '22 at 07:07

This answer is still relevant. My case: Windows 10 Host, Windows 11 guest. Upload was slow, had to disable "large send offloading" on the windows 11 VM to have full upload capabilities.

Go to the "network connections", choose the Ethernet connection, "Properties" > "Configure" > "Advanced"

score 1 · Answer 3 · answered Aug 12 '21 at 14:17

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For Windows 10 21h1 this worked for me: PICUTRE:

answered Aug 12 '21 at 14:17

Windoof93

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Some people cannot view images. Please make sure all relevant information is posted in your answer in text form. – Michael Hampton Aug 12 '21 at 14:35

score 1 · Answer 4 · answered Jun 07 '23 at 12:00

Disabling on the host and guest can sometimes fix this. To disable it on an Ubuntu 22 guest, do the following:

`sudo nano /etc/network/if-up.d/disable-lro.s`

then add this to that file:

#!/bin/sh
ethtool -K eth0 lro off

Make sure the permissions are correct:

sudo chmod +x /etc/network/if-up.d/disable-lro.sh

Then reboot Ubuntu.

score 0 · Answer 5 · answered Jun 07 '23 at 21:52

This ultimately worked for me:

sudo apt install ethtool
sudo ethtool -K eth0 tso off

You can check whether it worked by running:

sudo ethtool -k eth0 | grep 'tcp-segmentation-offload'
wget -O - https://raw.githubusercontent.com/sivel/speedtest-cli/master/speedtest.py | python

I now get the full upload speed of my ISP, which is 40:

Hyper-V virtual machine upload speed unbelievably slow

5 Answers5