Help, please: My 40 GbE switch-to-server connections need use crossover(?!) MPO cables...


New Member
Apr 3, 2017
... and I swear, last week they only worked with Type 'A' or straight MPO cables.

My switch-to-switch connections continue to only communicate with type 'B' (crossover) MPO cables.

The main thing to have changed from last week, is that I upgraded the firmware on 2 servers' components:

Dell Mellanox 6RKNM dual QSFP NIC --> 2.40.7000
Lenovo Mellanox ConnectX-3 NIC FRU 00D9552 --> 2.35.5100

And both switches:

Cisco Nexus 3064PQ-10GX from 6.0.2.U6.9 to 6.0.2.U6.8
Cisco Nexus 3132Q-40GE from 6.0.9.U6.9 to 7.0.3.I4.4

Does anyone have any idea if perhaps it was a Cisco decision to reverse the polarity requirements (documentation?) or is there some setting that I must have changed?

Can some one point me in the right direction?

I need to be sure I understand how this could happen as I can't have fiber cable polarities flip on me in a live datacenter, especially when it comes to MPO cables.

Thanks again!