> Why link speed is undefined? > Old kernel? > Kernel mlx5 driver issue? > Do you know? Seems to be a bug in kernel mlx5 driver: http://mails.dpdk.org/archives/users/2020-March/004758.html I still think this test is too strict, and from what I can see mlx4 PMD do not implement it (even if it uses 2 syscalls too). ben