Hi!
In CRS309 with two DAC speed stays less than 2.6 Gb/sec.
Even when I clear config speed is 2.1, but if I switch off RSTP speed is 2.6, both with RouterOS and SwOS.
How can I get 10GB speed?

I think single stream is limited, you might want to test with multiple streams:

iperf -c 192.168.9.21 -P 5

I think single stream is limited, you might want to test with multiple streams:

iperf -c 192.168.9.21 -P 5

I've tried. Even 8 stream. With different packet size. Without result.

But i have got this. and I have no idea what it mean

Change the MTU to 9000.

Disable flow control and test again

Thank you everyone!
I did all of the above and this (https://www.reddit.com/r/sysadmin/comme ... d_my_slow/)
And now I have 9.1 Gb/sec.