We have in our lab a Mellanox EDR SB7700 switch connected to a Mellanox FDR SX6018 switch and an Intel server running RHEL 6.5 with Mellanox HCA ConnectX-3. We are using the following cables:
PN MC2207130-001 (QSFP passive copper VPI )
PN MCP1600-E001 (QSFP28 passive copper EDR)
The setup works great!
Thanks for the info! I had tried a somewhat similar setup but was unable to bring the link up. Turns out that was due to a configuration mistake on my part. After correcting the mistake, I am getting EDR<->FDR links to work as well.