What the model of your QSFP+ cable?
Could you check your HCA's PSID?
Thanks for your replying.
The card Part number: MCX354A-FCBT (not sure how to find the PSID, ibstat returns nothing under 16.04, was fine under 14.04, will reboot with 14.04 next week).
The cable is a MC2207130-002 Passive Copper Cable VPI Up To 56Gb/s QSFP 2m. (https://www.mellanoxstore.com/products/mellanox-mc2207130-002-passive-copper-cable-vpi-up-to-56gb-s-qsfp-2m.html)
I found the PSID with mstflint: MT_1090120019
Your adapter is infiniband HCA(Host Channel Adapter).
Your cable also FDR14 56Gb Infiniband copper cable.
It seems all of your equipment is normal.
Here is another questions.
01. How did you connect 10Gb ethernet?
02. Do you have QSA module?
03. What's your switch system?
04. Did you check your HCA's firmware version and port configuration mode?
Yes, using QSA module: MAM1Q00A-QSA Cable Module ETH 10GbE 40Gb/s to 10Gb/s QSFP to SFP+ (https://www.mellanoxstore.com/products/mellanox-mam1q00a-qsa-cable-module-eth-10gbe-40gb-s-to-10gb-s-qsfp-to-sfp.html)
No I did not check the firmware version. But this card was before in a Windows box and was working fine with the 40G.
The thing I find odd is that a few seconds after inserting the 10G (not connected at the other end) I see a kernel message and a network device becomes available. Whereas with the 40G, nothing happens at all.