Forum Discussion

Jeff_Riechers's avatar
Jeff_Riechers
Copper Contributor
Mar 04, 2024

VMXnet3 Server 2025 performance issues

Had an odd one crop up today.  I updated my Server 2025 template to the 26063.1 release and then sysprepped it.  Converted it back to a new VM and network performance was .25 Mbps down.  Both on my l...
networking
philippeannet's avatar
philippeannet
Copper Contributor
Mar 12, 2025

Got a similar issue with a W11 VM on an Intel MBP (MacOS 15.3) with Fusion Pro... Speedtest.net gets me a solid 450-500Mbps upload, but barely half of that in download (???????????), although the host gets 6-700Mbps in download... I played with all possible offloads in the adapter settings (VMXnet3 and e1000), same story, pretty incomprehensible !!

MysticFoxDE's avatar
MysticFoxDE
Brass Contributor
Mar 13, 2025

Hi philippeannet,

on an Intel MBP (MacOS 15.3) with Fusion Pro

😯 ... 👍👍👍 ... You are definitely very brave, I like that!

Now to the important things.

With an uplink speed of 1 Gbit/s, you should only use VMXnet or E1000 vNIC and never VMXnet3, as this is intended for uplinks of 10 Gbit/s or more.

In addition, you should deactivate the Defender and also the phishing protection of W11 as a test, as they also like to steal a lot of performance and slow you down considerably. 😔     

Then you could deactivate the RSC on the W11 in particular, but also the RSS as a test.

netsh int tcp set global RSS=Disabled
netsh int tcp set global RSC=Disabled

 

Otherwise you can also run the following script in the VM.

https://github.com/MysticFoxDE/WINDOWS-OPTIMIZATIONS/blob/main/W10ANDW11-NETWORK-TCP-DESUBOPTIMIZATION.ps1

😉

 

Best Regards from Germany

Alex

Resources