Bandwidth Cap Issue on Windows Server 2025 with VirtIO NIC

[shakibshalim74]

Dear Community,

I am facing a bandwidth limitation issue on a Windows Server 2025 VM using a VirtIO network adapter in CloudStack. The VM detects the VirtIO NIC properly and remains stable after reboot, but the network throughput is capped at around 180–200 Mbps during iperf3 tests.

Has anyone experienced this issue or can suggest additional tuning steps for improving VirtIO network performance on Windows Server 2025 within CloudStack?

Any guidance or suggestions would be greatly appreciated.

Thank you.

Regards,
Shakib Salim

[SviridoffA]

Hi @shakibshalim74, please take a look at this discussion. #11600

[shakibshalim74]

In our current CloudStack environment (Version: 4.19.3.0), the global settings are configured as follows:

1. Network Offerings: 200 MB (cloud.network_offerings)
2. System VM Service Offerings: 200 MB (cloud.service_offering)

We have also created a compute offering, set the Network Rate to 2000 MB. Using this offering, we launched several Windows and Linux VMs, which work correctly and achieve up to 1 Gbps network bandwidth.

The issue appears only when attaching a Windows VM NIC with VirtIO(0.1.285), where the VM becomes limited to 200 MB bandwidth, despite the higher rate set in the offering. Without VirtIO, the same VM reaches full speed.