NVIDIA Mellanox MCX4421A-ACAN ConnectX-4 Lx EN 25GbE Dual-Port OCP Network Adapter: This is an OCP 2.0 mezzanine network interface card (NIC) based on the Mellanox ConnectX-4 Lx EN controller, providing two 25 Gigabit Ethernet (25GbE) SFP28 ports over a PCIe 3.0 x8 host interface. This is the OCP form-factor variant; it is NOT a standard PCIe full-height/low-profile add-in card and will not install in a conventional PCIe slot.
Engineering context. The ConnectX-4 Lx silicon supports hardware offloads for TCP/UDP/IP checksums, TSO, LRO, RSS over IPv4/IPv6, RoCE v1 and v2, NVGRE/VXLAN/GENEVE tunnel offload, and SR-IOV with up to 256 virtual functions. PCI Express Gen3 x8 provides ~63Gb/s of usable host bandwidth — sufficient to run both 25GbE ports at full duplex.
Deployment & use cases. Designed for OCP server platforms in hyperscale and enterprise data centers, virtualization (VMware ESXi, KVM, Hyper-V) with SR-IOV pass-through to guests, NVMe-over-Fabrics initiators using RoCE, OpenStack and Kubernetes nodes, and 25GbE access into Spectrum SN2000-series or other 25GbE leaf switches.
Technical specifications.

Controller: NVIDIA Mellanox ConnectX-4 Lx EN
Ports: 2 × SFP28 25GbE (also supports 10GbE / 1GbE per port)
Host interface: PCI Express 3.0 x8 (8.0GT/s)
Form factor: OCP 2.0 mezzanine (no PCIe edge bracket)
Stateless offloads: TSO, LRO, RSS, checksums (IPv4/IPv6)
Tunnel offloads: VXLAN, NVGRE, GENEVE
RDMA: RoCE v1 and RoCE v2
Virtualization: SR-IOV (up to 256 VFs)
Wire protocols supported: 25GbE, 10GbE, 1GbE
Compliance: RoHS R6

Compatibility & constraints. Requires an OCP 2.0 mezzanine slot. SFP28 cages accept 25GbE SFP28 transceivers/DACs/AOCs and are backward-compatible with 10GbE SFP+ optics; they do NOT accept QSFP/QSFP28 modules or carry 40GbE/100GbE traffic. Driver support is provided by Mellanox MLNX_OFED for Linux and Mellanox WinOF-2 for Windows Server.
Why TES. Each unit is bench-tested by experienced technicians for full link-up at 25GbE on both ports prior to shipment and ships in refurbished condition with minimal cosmetic wear. Order handling time is 1–3 business days. Browse our full networking catalog at T.E.S IT-SOLUTIONS.