QSFP28 AOC cables not working in MLAG

Hi,

I have a number of QSFP28 AOC fibre 1x4 breakout cables that used to work fine in Onyx 3.9.1908, but since upgrading to Onyx 3.10.X these cables no longer work. The cables are all Mellanox branded and bought from FS.

        identifier             : QSFP28
        cable/module type      : Active optical cable
        ethernet speed and type: 100G AOC, FEC based
        vendor                 : Mellanox
        cable length           : 3m
        part number            : Q-4S28AO03
        revision               : A3
        serial number          : C2205036149

Since upgrading the link diagnostics just say “Cable speed not enabled” and there is no link up. It doesn’t matter if the other end is plugged in or not.

If I set the interface to “speed auto” I get “Negotiation failure”, so that seems to make a difference, but this interface needs to be an MLAG member, so I can’t set it to auto.

After much Googling I have not been able to find out what this error means or how to resolve this problem.

The interface on my test switch has no config beyond the default.

  Admin state                      : Enabled
  Operational state                : Down
  Last change in operational status: Never
  Boot delay time                  : 0 sec
  Description                      : N/A
  Mac address                      : 1c:34:da:32:f2:d8   
  MTU                              : 9216 bytes (Maximum packet size 9238 bytes)
  Fec                              : auto
  Operational Fec                  : N/A
  Flow-control                     : receive off send off
  Supported speeds                 : 1G 10G 25G
  Advertised speeds                : 25G
  Actual speed                     : Unknown
  Auto-negotiation                 : Enabled
  Width reduction mode             : Unknown
  Switchport mode                  : access
  MAC learning mode                : Enabled
  Forwarding mode                  : inherited cut-through

Can anyone explain what is going on here?

Hi Cliff,

From the problem description, the issue seems to be related to auto-negotiation of the link, could you try to hard-code the link speed and duplex mode on both the switch side and the directly connected device, and check if that makes any difference?
The other thing is that since the cables are from FS, it could be locked as 3rd party transceiver. Could you run the command “fae cable-stamping-unlock eth_100g” under config mode, and check if that makes any difference? If the issue still persists, please open a case with support team to further investigate the issue.

Thanks!