How to disable Smart AN on CX6 adapter

How to disable Smart AN on CX6 adapter

Hi Ankit,

To disable Auto Negotiation, you need to install the MFT package from the link below.

Note: MFT is part of MLNX_OFED, so if you have the driver installed on the system, you should already have MFT.

Then, you can use the mlxlink tool.

mlxlink UM:


mst start

To get the MST device:

mst status -v

To query current configuration:

mlxlink -d

To Set Auto Negotiation to OFF and force the speed:

mlxlink -d --link_mode_force --speeds


mlxlink -d /dev/mst/mt4119_pciconf0 --link_mode_force --speeds 25G

Then you must toggle the link so the above changes will take place:

mlxlink -d -a TG

Then query again:

mlxlink -d

You can also change FEC type to be the same as the switch, as FEC type should be identical on all end points:

Change to RS FEC:

mlxlink -d -fec RS -fec_speed

Or - change to FC FEC:

mlxlink -d -fec FC -fec_speed

Then toggle:

mlxlink -d -a TG