Question about transceiver for ConnectX-4 Lx EN (MCX4121A-XCAT)

I’m trying to solve a connectivity problem in the most economical way. I’ll provide some details first, but my question is listed near the bottom of this post in bold font if you want to skip ahead.

I have three Mellanox ConnectX-4 Lx EN (P/N MCX4121A-XCAT) which is 10G NIC with dual SFP28 ports. I don’t have enough equipment to justify getting a good 10G switch, so I’m connecting directly between servers using Mellanox MC3309130-003 cable (passive copper cable with connectors compatible with SFP28 ports).

Everything’s working fine with one exception. I need to connect only a single port of one of my ConnectX-4 Lx EN NICs to a switch so that my virtual machines can access the rest of my network and the internet. I have a HPE 2920-48G (J9728A) 48-port gigabit switch that has an optional 10G module installed (J9732A). This module has dual port 10GBase-T with RJ-45 connectors.

So the problem is that I need to connect from SFP28 port on my ConnectX-4 NIC to 10GBase-T RJ-45 port on my HPE switch. I want to connect between them using a CAT6a network cable. That CAT6a cable will fit the RJ-45 port on the switch, but it won’t fit on the SFP28 port on the NIC.


Is it possible (and safe) to plug a transceiver directly into one of my SFP28 ports on my ConnectX-4 NIC?

Unfortunately, I’ve not found any “officially supported” product for this scenario. However, I found a 10G transceiver on that converts from SFP+ form factor to RJ-45. SFP+ has the same form factor as SFP28 but only supports speeds up to 10G (whereas SFP28 supports 25G). tech support claims it’s compatible with my ConnectX-4 NIC because only 10G speed is needed in my case, so I’m willing to give it a shot.

FS for Mellanox MFM1T02A-T Compatible, 10GBASE-T SFP+ Copper RJ-45 30m Transceiver Module (Standard) #89584

Has anyone done something this before using ConnectX-4 Lx EN NIC? If yes, would you mind telling me which transceiver worked successfully? As mentioned above, I’m trying to connect using copper network cable (not optical) with RJ-45 connectors.

Hello Ashok,

Thank you for posting your inquiry on the NVIDIA Networking Community.

Based on the information provided, we noticed that you also opened an official NVIDIA Networking Support ticket which is being handled by one of our engineers.

He will continue to support you through the official ticket.

Thank you and regards,

~NVIDIA Networking Technical Support