Windows VM 25GBPS Negotiation and Speed Capping Problem

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P10i

New Member
May 20, 2025
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Hi,

I have a Dell PowerEdge R640 Host on which I have installed Proxmox. It has 25GBPS Link on Mellanox Card and it is hosted on Redswitches.

I have only 2 vms on it, one is ubuntu and one is windows 2022. On Proxmox host I am getting full 25GBPS Speed, On Ubuntu VM I am getting full 25GBPS but on windows 2022 VM I am getting only 3GBPS.

Windows
[SUM] 0.00-9.72 sec 4.22 GBytes 3.73 Gbits/sec

Ubuntu VM
[SUM] 3.00-3.46 sec 1.25 GBytes 23.5 Gbits/sec 1089

I also noticed for virtio adapter the negotiated speed in windows vm is 10GBPS and on ubuntu its not a problem on same host.

1747756512850.png

I followed related articles and guides, I have disabled ASPM and saerver is on performance mode and the speed is not affected on VM in any way.
M

Post in thread '25GbE network capped at 10GbE'

cheiss said:
Hi,


how exactly are you running iperf3? Are you using the -P, e.g. iperf3 -P8 ...
This enables parallel stream, as your machine might be just capped by the CPU in this regard.
Click to expand...

yes exactly, I also had this idea.
However, I tested iperf with all variants:

iperf3 (with no options)
iperf3 -P 4
iperf3 -P 8
iperf3 -P16

however, the difference between all the variants was nonexistent to negligible.

I have my Proxmox connected to a bridge, and the bridge is connected to a bond, and the bond contains the 25G interface, as well as an 1G "emergency failover" interface, in...
B

Thread 'I AM GOING CRAZY 2GBIT 10G WHY.....'

First off i live in Communist Australia, we have an NTU "network termination unit" aka bridge media converter, i have a nic in passthrough that is assigned to a vm with opnsense the lan has a virtio nic that does show up as 10G, i have a fileserver vM with virtio nic 10G plus the proxmox bridge has two 10G fibre Intel 520 googus.

speed test using iperf3 on all vm's 25G wow ok..... with the exception of opnsense if i perf that 2Gb i am talking about the LAN IP.

the 10G 520 has a direct connection to my workstation which is running Windows 10 64bit PRO. same card but cisco OEM.

Using AOC...

I also upgraded network drivers from latest virtio iso. I am not getting even full 10gbps on windows and on ubuntu I am getting full speed, so opening a ticket to them is useless as this is clearly something from proxmox side not their side.

What is wrong here? Any help on this problem will be appreciated.

Thank you
 
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