Network speed: USB redirecting vs NAT

A new toy just arrived.

A USB type-c 2.5Gb ethernet adaptor.

When test at host, I got:
iperf3 -c remote -p port

When I test in a VM, using default NAT
Almost same score.

When I redirect the USB device to the guest:

I am using virt-manager for the test.

How to improve USB redirection network speed?


On the USB Controler settings you are using which settings?

USB3, which is default for Fedora Guests.

For the same device, if using “Add Host USB device” (when guest is not running), instead of USB Redirection (when guest is running).

I got about 900Mbits / sec.

I guess this is the way to go. Please check the max transfere rate between USB3 and USB-C . This could be the difference of speed you get (a bottle neck).
If you use NAT, you are using the USB-C of your host and the Name Address Translation is over IP and over your network of the Guest. That’s why I believe it is so fast.

Yes, until a better way available, adding Host Device is the way to go.

In theory, USB3 is 5Gbit / sec, which is the same as my host type-c interface speed.

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