DELL CX4121C ConnectX-4 Lx 25Gbps Dual Port SFP Daughter Card 20NJD

Dell ConnectX-4 Lx 25Gbps Dual Port Daughter Card

The Dell CX4121C is a dual-port 25Gbps SFP daughter card built on the Mellanox ConnectX-4 Lx controller. It installs into a compatible Dell server slot to add two 25GbE network connections for high-throughput workloads. The part number is 20NJD and the interface is PCI-Express.

Installation notes and common issues

This daughter card mounts directly into a supported Dell server mezzanine or riser slot, not a standard PCIe add-in slot, so verify the server service manual for the correct connector. No SFP transceivers or cables are included; they must be sourced separately to match the link type and distance. Firmware should be updated through the server lifecycle controller after installation.

Compatibility checklist before ordering

Confirm the target Dell server model lists the CX4121C or part number 20NJD in its qualified hardware matrix. Ensure an appropriate mezzanine or riser bay is free and that the chassis airflow meets the server thermal guidelines. Check that the operating system or hypervisor has driver support for the ConnectX-4 Lx controller at the required version.