interconnecting QSFP28 and QSFP+

We’ve bought connectx-4 LX 50gbE card which apparently has QSFP28 port and we’d like to get it connected to our switch which has QSFP+ ports only. Is this possible at all? Thanks.

What a miracle! QSFP+ can actually be plugged into QSFP28, but you have to be careful selecting the speed as mellanox’s proprietary 56GigE speed isn’t supported and you have to force 40GigE. What a pity you can’t have 50, but this is still better than having no link at all 😄