Slow Network performance on some VM

mspinolo

Member
Dec 16, 2019
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Hi,

I have a Core i5-9900T / 32GB ram with 5 Intel-210 Nics.

4 of those NICS are on a PCI-E board, while 1 is embedded in the motherboard.

I get different results in terms of speed with IPERF3:
- on board NIC being 1Gbit/s both directions
- NICS on PCI-E board being 1Gbit/s when in server mode, 100Mbit/s when client mode

They are connected to the same switch: i tried to swap ports / cables with no changes.
I also tried moving a VM in proxmox from one NIC to the other and confirmed this behavior is NIC based.

I am not sure why and what to look for to understand the reason, can anyone help?