RJ-45 Console and I²C interfaces are integrated in the same connector. Due to that, connecting any cable other than the Mellanox supplied console cable may cause an I²C hang.
Using uncertified cables may damage the I²C interface. Refer to the Replacement Parts Ordering Numbers appendix for harness details.
RJ-45 CONSOLE and I²C Pinout
RS232 harness cable (DB9 to RJ45) is supplied to connect a host PC to the switch’s RJ-45 Console port.
RJ45 to DB9 Harness Pinout