How to Reveal a Missing Mellanox 25G NIC in UEFI on Dell PowerEdge C6420

Background

A Dell PowerEdge C6420 high‑density 2U server equipped with dual‑socket CPUs and OCP‑compliant 25 Gbps Mellanox ConnectX‑4 LX‑EN NICs failed to show the network adapter in the BIOS Device Settings screen when the operating system was upgraded using UEFI mode, preventing PXE boot configuration.

Solution (Linux example)

Download the Mellanox Firmware Tools (MFT) package from the Mellanox management tools page: http://www.mellanox.com/page/management_tools.

Select the Linux RPM distribution package (e.g., mft-4.11.0-103-x86_64-rpm.tgz) and copy it to a Linux host.

Extract the archive: tar zxvf mft-4.11.0-103-x86_64-rpm.tgz Install the RPM (adjust the command for the specific distribution, e.g., rpm -ivh mft-*.rpm for RPM‑based systems).

Start the MFT daemon: mst start Verify the daemon is running and obtain the device identifier: mst status The device appears as mt4117_pciconf0 (or mt4117_pciconf0.1 for a second port).

Enable the NIC for UEFI by setting the required configuration flags. Execute the following commands, adjusting the device path if a second NIC is present:

mlxconfig -d /dev/mst/mt4117_pciconf0 set UEFI_HII_EN=1

mlxconfig -d /dev/mst/mt4117_pciconf0.1 set UEFI_HII_EN=1

mlxconfig -d /dev/mst/mt4117_pciconf0 set EXP_ROM_UEFI_x86_ENABLE=1

mlxconfig -d /dev/mst/mt4117_pciconf0.1 set EXP_ROM_UEFI_x86_ENABLE=1

Reboot the server, enter the BIOS/UEFI setup, and verify that the Mellanox NIC now appears in the Device Settings menu.

Proceed with PXE boot configuration as required.

Applicable Conditions

Mellanox ConnectX‑4 LX‑EN dual‑port 25 Gbps SFP+ adapters (part number 9R8DF).

Supported Dell PowerEdge models: C6420, R540, R740xd2, R7415, R6415.