Identity & Definition
The Dell 020NJD is a 25GbE enterprise network interface card (NIC) in refurbished condition. This dual-port SFP28 Ethernet adapter is based on Mellanox ConnectX-4 Lx (CX4121C) technology and connects via PCIe 3.0 x8 for high-bandwidth, low-latency server networking. The 020NJD is a Dell OEM part number — the Mellanox equivalent model is MCX4121A-ACAT. It is NOT an InfiniBand adapter, NOT a single-port card, and NOT a QSFP28 form factor device.
Engineering Context
The 020NJD delivers 25Gb/s per port (50Gb/s aggregate) using NRZ signaling over its two SFP28 interfaces. The adapter connects to the host server via a PCIe 3.0 x8 slot providing up to 8 gigatransfers per second of bus bandwidth. ConnectX-4 Lx technology supports hardware offloads including SR-IOV for NIC virtualization, RoCE (RDMA over Converged Ethernet) v2 for low-latency storage and cluster communication, and stateless TCP/UDP/IP offload for reduced CPU overhead. The card ships in low-profile (LP) bracket configuration.
Deployment & Use Cases
The 020NJD is designed for 25GbE server connectivity in Dell PowerEdge environments. Typical deployment scenarios include VMware ESXi and Hyper-V virtualization hosts requiring SR-IOV passthrough to VMs, NVMe-oF and iSCSI storage network connections using RoCE v2, server-to-ToR switch uplinks in 25GbE access-layer fabrics, and high-density cloud compute nodes in Dell PowerEdge R640, R740, R740xd, R940, and C-series chassis. The dual-port design provides network redundancy or link aggregation.
Technical Specifications

Dell Part Number: 020NJD (also referenced as 20NJD)
Mellanox Model: CX4121C (ConnectX-4 Lx)
Adapter Type: 25GbE Ethernet Network Adapter
Port Count: 2 (Dual-Port)
Port Type: SFP28
Data Rate: 25Gb/s per port (50Gb/s aggregate)
Host Interface: PCIe 3.0 x8
Form Factor: Low-Profile (LP) PCIe Add-in Card
Protocols: 25GbE, 10GbE, RoCE v2, SR-IOV
Condition: Refurbished

Compatibility & Hard Constraints
The 020NJD is a Dell OEM adapter and is validated for Dell PowerEdge servers including R640, R740, R740xd, R940, C4140, FC630, FC640, and C6320 platforms. It requires a PCIe 3.0 x8 or wider slot (x16 physical also works). The SFP28 ports accept 25GbE SFP28 transceivers, 25GbE SFP28 DAC cables, or 10GbE SFP+ optics (backward compatible at 10GbE). It is NOT compatible with QSFP28 or QSFP56 cabling. The Mellanox-branded equivalent for non-Dell servers is MCX4121A-ACAT. Dell firmware and drivers may differ from Mellanox reference firmware.
Why Choose T.E.S IT-SOLUTIONS
Every 020NJD adapter sold by T.E.S IT-SOLUTIONS is functionally tested and verified before shipment. Our team provides technical consultation on Dell PowerEdge NIC compatibility, SFP28 transceiver selection, and deployment planning. Orders ship within 1–3 business days with worldwide delivery and protective packaging.