10G ConnectX-4 Lx NICs can be flashed to 25G with the right firmware. This is useful if you have a 10G NIC and want to upgrade to 25G without buying a new NIC. This article will guide you through the process of flashing a 10G Mellanox ConnectX-4 Lx NIC to 25G.

Warning: Do not try this on MCX4121C. It will brick the NIC.

1. Download firmware from Firmware for ConnectX®-4 Lx EN. Choose MCX4121A-ACUT. I will assume the firmware file is named fw-ConnectX4Lx-rel-14_32_1010-MCX4121A-ACU_Ax-UEFI-14.25.17-FlexBoot-3.6.502.bin.

   If you are wondering what’s the difference between models, here’s a table for ConnectX-4 Lx cards (original document). You should choose 25G models to flash to.

   Max Network Speed	Interface Type	Supported Ethernet Speeds (GbE)	Host Interface	Additional Features	OPN
   1x 10GbE	SFP28	10, 1	PCIe 3.0 x8		MCX4111A-XCAT
   2x 10GbE	SFP28	10, 1	PCIe 3.0 x8		MCX4121A-XCAT
   2x 10GbE	SFP28	10, 1	PCIe 3.0 x8	Host Management, UEFI Enabled	MCX4121A-XCHT
   1x 25GbE	SFP28	25, 10, 1	PCIe 3.0 x8		MCX4111A-ACAT
   1x 25GbE	SFP28	25, 10, 1	PCIe 3.0 x8	UEFI Enabled	MCX4111A-ACUT
   2x 25GbE	SFP28	25, 10, 1	PCIe 3.0 x8		MCX4121A-ACAT
   2x 25GbE	SFP28	25, 10, 1	PCIe 3.0 x8	UEFI Enabled	MCX4121A-ACUT
   1x 40GbE	QSFP28	40, 25, 10, 1	PCIe 3.0 x8		MCX4131A-BCAT
   1x 50GbE	QSFP28	50, 40, 25, 10, 1	PCIe 3.0 x8		MCX4131A-GCAT

2. Download and install NVIDIA Firmware Tools (MFT).

3. mst start

4. mst ststus You will see you MST device, e.g. /dev/mst/mt4117_pciconf0. I will use this device path in this article. If your path differs from this, please change it accordingly.

5. Save GUID, MAC: flint -d /dev/mst/mt4117_pciconf0 query full > flint_query.txt

6. Save hardware info: flint -d /dev/mst/mt4117_pciconf0 hw query > flint_hwinfo.txt

7. Save current firmware: flint -d /dev/mst/mt4117_pciconf0 ri orig_firmware.bin

8. Save current firmware config: flint -d /dev/mst/mt4117_pciconf0 dc orig_firmware.ini

9. Save current PXE ROM (if exists): flint -d /dev/mst/mt4117_pciconf0 rrom orig_rom.bin

10. Save current PCI VPD: mlxburn -d /dev/mst/mt4117_pciconf0 -vpd > orig_vpd.txt

11. flint -i fw-ConnectX4Lx-rel-14_32_1010-MCX4121A-ACU_Ax-UEFI-14.25.17-FlexBoot-3.6.502.bin verify

12. flint -i fw-ConnectX4Lx-rel-14_32_1010-MCX4121A-ACU_Ax-UEFI-14.25.17-FlexBoot-3.6.502.bin -d /dev/mst/mt4117_pciconf0 -allow_psid_change burn

Reboot you machine. You should see your NIC is now have 25G speed.

Bonus:

• To change MAC address: flint -d /dev/mst/mt4117_pciconf0 -mac 02c90abcdef0 sg
• To change GUID: flint -d /dev/mst/mt4117_pciconf0 -guid 0002c9000abcdef0 sg