This article covers Mellanox ConnectX-4 Lx EN MT27711A0イーサネットコントローラー.

Overview

The LinksTek CX4121A is a dual 25GbE SFP28 fiber port network card built around the Mellanox ConnectX-4 Lx EN MT27711A0 controller. Designed for data centers and high-end workstations, it supports advanced features like RDMA over Converged Ethernet (RoCE) and SR-IOV for virtualized environments. What makes this card stand out is its ability to deliver up to 50Gbps aggregate bandwidth through two 25GbE ports while using a PCIe 3.0 x8 interface. For users building cloud storage, virtualization hosts, or high-speed file servers, this offers an excellent price-to-performance ratio compared to enterprise-grade alternatives.

Connectivity & Compatibility

Interface: PCI Express 3.0 x8 (auto-negotiates down to x4/x2/x1 lanes, backward compatible with PCIe Gen 2.0) Ports: 2x SFP28 fiber ports (simultaneous 25GbE operation) Supported OS: Windows 11/10 64-bit, Windows Server 2012/2012R2/2016/2019/2022/2025, RHEL, CentOS, FreeBSD, VMware, and other Linux kernel-based systems Remote boot: RoCE, PXE, iSCSI Cable compatibility: SFP28 transceivers, SFP28 DAC cables, SFP28 AOC cables with PAM4 Ethernet links Standards: IEEE 802.3by (25Gb/s), IEEE 802.3ae (10Gb/s), IEEE 802.3az (Energy Efficient Ethernet), IEEE 802.3ad/802.1AX (link aggregation), IEEE 802.1Q (VLAN tagging), jumbo frames (9.6KB)

Product Info

Released around 2025, the LinksTek CX4121A is available on Japan for approximately ¥14,233. Warranty typically covers one year from the seller. The package includes the card only — SFP28 modules and cables must be purchased separately. This card sits in the entry-to-mid-range segment for 25GbE networking. While the Mellanox ConnectX-4 Lx chipset is a proven data-center component, the consumer-friendly pricing makes it accessible for prosumers and small businesses. Compared to Intel XXV710 or Broadcom alternatives, it offers enterprise features like RoCE and SR-IOV at a lower cost.

Best Use Cases

Home lab enthusiasts building NAS or file servers: The 25GbE bandwidth eliminates bottlenecks during simultaneous multi-client access. However, you'll need a compatible switch and SFP28 modules, making the total investment higher than 10GbE setups. IT engineers managing virtualized environments: SR-IOV allows direct NIC assignment to virtual machines, boosting network performance in VMware or Hyper-V deployments. * Creative professionals and researchers handling large datasets: Transferring 4K/8K video files or scientific data becomes significantly faster with 25GbE — but ensure your storage subsystem (NVMe SSDs) can keep up.

Things to Consider

This card requires a PCIe 3.0 x8 or larger slot on your motherboard. Installing it in an x4 slot will halve the available bandwidth, preventing full 25GbE performance. Also, SFP28 transceivers or DAC cables are not included — verify compatibility with your switch before purchasing. On Windows, you'll need to install the WinOF-2 driver from Mellanox's official site; the standard Ethernet driver may not recognize the card. Linux users should install OFED (Open Fabrics Enterprise Distribution) for optimal performance, though many distributions include the driver in the kernel. ## FAQ
Q: Can I use 10GbE SFP+ modules with this card? A: Yes, the SFP28 ports are backward compatible with 10GbE SFP+ modules. Speed will be limited to 10Gbps in that case. Q: Is this card suitable for gaming PCs? A: Technically yes, but it's overkill for gaming. Most home internet connections are 1Gbps or slower, so you won't benefit from 25GbE. It's best for local high-speed transfers between NAS and workstations. Q: Does it work with Linux out of the box? A: Generally yes. The Mellanox ConnectX-4 Lx has in-kernel driver support for most major distributions including RHEL, CentOS, Ubuntu, and Debian. For advanced features like RoCE, installing OFED is recommended.

Product Disclosure (Amazon)

  • Manufacturer: LinksTek
  • Seller: Amazon US
  • Fulfilled by: Amazon US
  • ASIN: B0FTXQF98M
  • Note: This article covers a manufacturer-made product based on Amazon listing details.