NVIDIA Mellanox MCX4131A-GCAT ConnectX-4 Lx EN Single-Port QSFP28 50GbE Adapter: This is a single-port Ethernet network interface card based on the ConnectX-4 Lx EN ASIC. The QSFP28 port runs at 50GbE (2x25G NRZ) and the host interface is PCIe 3.0 x8. The card ships with a tall (full-height) PCIe bracket. NVIDIA P/N 900-9X429-0015-0T0. This is an Ethernet-only (EN) card — it is not VPI and does not support InfiniBand. This is a refurbished unit, not a new-sealed factory part.
Engineering Context
50GbE on ConnectX-4 Lx is implemented as 2x25G NRZ over the QSFP28 cage — only two of the four lanes carry traffic at this rate. The card supports stateless TCP/UDP/IP offloads, hardware VXLAN/NVGRE/GENEVE encap-decap, RoCE v1/v2 for RDMA over Ethernet, ASAP² accelerated switching for OVS offload, and SR-IOV with up to 256 virtual functions. PCIe 3.0 x8 at 8GT/s provides 64 Gb/s of host bandwidth, sufficient for 50GbE wire-rate traffic. The QSFP28 port is also backward compatible with 25GbE (1x25G), 40GbE (4x10G), and 10GbE.
Deployment & Use Cases
50GbE host connectivity in NVIDIA Spectrum-based fabrics. RoCE-accelerated storage clients for NVMe-oF, iSER, and SMB Direct. Hypervisor uplinks for VMware ESXi, KVM, and Hyper-V where overlay offload is needed. SDN data-plane offload via OVS-DPDK and ASAP². Cost-effective step up from 40GbE for sites that want better $/Gb without moving to 100GbE. AI/ML inference nodes and analytics workers needing >40GbE.
Technical Specifications
OEM: NVIDIA Mellanox
Part Number: MCX4131A-GCAT
NVIDIA P/N: 900-9X429-0015-0T0
Controller: ConnectX-4 Lx EN
Ports: 1x QSFP28
Data Rate: 50GbE (2x25G NRZ)
Backward Rates: 40GbE, 25GbE, 10GbE
Host Interface: PCIe 3.0 x8 (8GT/s)
Bracket: Tall (full-height)
Form Factor: Standard PCIe HHHL
Protocol: Ethernet (EN-only, not VPI)
Offloads: RoCE v1/v2, VXLAN, NVGRE, GENEVE, ASAP², SR-IOV (up to 256 VFs)
Condition: Refurbished — Tested by T.E.S IT-SOLUTIONS
Compatibility & Constraints
Requires a PCIe 3.0 x8 (or wider) slot. Compatible with NVIDIA Spectrum (SN2000) switches and any standards-compliant 50GbE/2x25G switch. The 50GbE rate is 2x25G NRZ — connect with QSFP28 50GbE DACs/AOCs or 50GBASE-SR2/LR2 transceivers; verify peer-side support for 2x25G mode. This SKU is rated to 50GbE — for 100GbE see the MCX4121A or MCX516A series. Does NOT support InfiniBand. Driver support: MLNX_OFED for Linux, WinOF-2 for Windows Server, native NMLX5 driver in VMware ESXi 6.5+. SR-IOV requires VT-d/IOMMU enabled in BIOS.
Why Choose T.E.S IT-SOLUTIONS
T.E.S IT-SOLUTIONS bench-tests every ConnectX-4 Lx adapter for link training at 50GbE, PCIe enumeration, and firmware integrity. T.E.S IT-SOLUTIONS ships globally with 1–3 business day handling and offers expert support on Spectrum fabric integration.