I am new on networking and I need help from community if possible.
I have a pair of Cisco QSFP 40/100 SRBD bi-directional transceivers that installed on Mellanox ConnectX5 100Gb Adapters, connected them via an OM5 LC type 1M (or 3M) fibre cable.
My two servers back-to-back setup is working fine with the 100Gb speed link testing (have linked; LEDs both sides are on, good test result with iperf test ultility). However whenever I tried to switch the same setup to 40Gb speed testing (via ethtool commands ethtool -s enp59s0f0 autoneg off speed 40000), I have no linked between both adapters.
The 100Gb or 40Gb speed testings were working fine on others 100Gb transceivers (Arista, Finisar, Intel,...or 100Gb DAC)