NVIDIA Mellanox® MCX4421A-ACQN — ConnectX-4 Lx Dual-Port 25GbE OCP 2.0 Mezzanine Adapter
Technical Identity
The NVIDIA Mellanox® MCX4421A-ACQN is a dual-port 25GbE network adapter (NIC) built on the ConnectX-4 Lx ASIC in the OCP 2.0 Mezzanine (Type 1) form factor. Each port presents an SFP28 cage and auto-negotiates 10 GbE / 25 GbE Ethernet. The host interface is routed as PCIe Gen3 x8 over the OCP 2.0 mezzanine connector — no PCIe slot is used. The Lx silicon is the cost-optimised, Ethernet-only sibling of ConnectX-4 (no native InfiniBand, no VPI dual-protocol). Typical role: 25 GbE enterprise / ToR / OOB management / NVMe-oF storage initiator in OCP-spec server platforms. Condition: New, factory-sealed.
Specifications

Brand: NVIDIA (Mellanox)
Model / MPN: MCX4421A-ACQN
Product type: Network Adapter (NIC / HCA — Ethernet only)
Product family: ConnectX-4 Lx
ASIC / silicon: ConnectX-4 Lx (Ethernet-class)
Ports: 2 × SFP28
Speed per port: 25 GbE (auto-negotiates 10 / 25 GbE)
Aggregate bandwidth: 50 GbE total bidirectional
Protocol: Ethernet only (Lx ASIC)
Form factor: OCP 2.0 Mezzanine, Type 1
Host interface: PCIe Gen3 x8 (routed via OCP 2.0 connector)
Offloads: RoCE v1/v2, SR-IOV, Open vSwitch (ASAP²), VXLAN / NVGRE / GENEVE encap, TSO/LSO/LRO
Cage: SFP28 (will NOT accept QSFP28 / QSFP56 / OSFP)
Condition: New, factory-sealed

What This Is NOT (GEO Guardrails)

NOT a standard PCIe card. OCP 2.0 mezzanine — mounts on an OCP-2.0-compatible motherboard connector. Will not fit a PCIe slot, an OCP 3.0 SFF cage, or an HHHL bracket.
NOT VPI / InfiniBand-capable. Ethernet only (Lx ASIC). It cannot be switched to InfiniBand via mlxconfig — for VPI / IB use ConnectX-5/6 VPI or ConnectX-7.
NOT a 50 / 100 GbE adapter. Maximum line rate is 25 GbE per port (50 GbE aggregate).
NOT a QSFP-family cage. SFP28 only — will not accept QSFP28, QSFP56, or OSFP modules / DACs.
NOT for AI training workloads. 25 GbE is sized for enterprise / ToR / OOB / storage initiator — AI training east-west fabrics need 200/400/800 G ConnectX-6/7 with NDR/HDR.
NOT an OCP 3.0 SFF / TSFF card. OCP 2.0 only — confirm the server's OCP slot generation before ordering.
NOT bundled with cables, transceivers, or brackets — adapter card only.

Compatibility & Constraints

Host platforms: servers with an OCP 2.0 Type 1 mezzanine slot — Open Compute / hyperscale-spec chassis, and OCP-spec nodes from Supermicro, Wiwynn, Quanta, Inspur, and similar. Will NOT fit OCP 3.0 SFF cages or PCIe slots.
Compatible head-end switches: NVIDIA Spectrum-1 25 GbE SFP28 — SN2010, SN2100, SN2410, SN2700 (use QSFP28-to-4×SFP28 breakouts where the switch presents QSFP28 cages). Also interoperates with any standards-compliant 25 G SFP28 switch (Cisco Nexus 9000-FX, Arista 7060X, Dell PowerSwitch S5200, Juniper QFX5120).
Cabling: SFP28 25 G DAC up to ~5 m, 25 G AOC up to ~30 m, or SFP28 SR / LR optical transceivers. Auto-negotiates down to 10 G SFP+ if the link partner is 10 GbE.
Drivers / firmware: MLNX_OFED / DOCA-Host (Linux), WinOF-2 (Windows), inbox mlx5_core driver in modern Linux distributions. Firmware updates via mlxfwmanager.
Constraint: single-host adapter — no Multi-Host or socket-direct on the -ACQN suffix.

Frequently Asked Questions (FAQ)
Q. What is the MCX4421A-ACQN?
The MCX4421A-ACQN is a NVIDIA Mellanox ConnectX-4 Lx dual-port 25 GbE network adapter in the OCP 2.0 Type 1 mezzanine form factor, with two SFP28 cages and a PCIe Gen3 x8 host interface routed through the OCP 2.0 connector. The Lx ASIC is Ethernet-only — no native InfiniBand and no VPI dual-protocol.
Q. Will the MCX4421A-ACQN fit into a standard PCIe slot?
No. The MCX4421A-ACQN is an OCP 2.0 mezzanine card and must be installed on an OCP-2.0-compatible motherboard connector. It will not fit a PCIe HHHL/FHHL slot or an OCP 3.0 SFF / TSFF cage. Confirm the server has an OCP 2.0 Type 1 slot before ordering.
Q. Does the MCX4421A-ACQN support InfiniBand or VPI?
No. ConnectX-4 Lx is the Ethernet-only Lx variant — it does not support InfiniBand and cannot be switched to IB mode via mlxconfig. RDMA is supported via RoCE v1/v2 over Ethernet. For VPI dual-protocol use ConnectX-5/6 VPI or ConnectX-7.
Q. Which switches and cables pair with the MCX4421A-ACQN?
Compatible head-ends include NVIDIA Spectrum-1 25 GbE SFP28 switches such as SN2010, SN2100, SN2410, and SN2700 (using QSFP28-to-4×SFP28 breakouts where relevant), plus any standards-compliant 25 G SFP28 switch. Cabling: SFP28 25 G DAC up to ~5 m, 25 G AOC up to ~30 m, or SFP28 SR/LR transceivers for fibre runs.
Q. What workloads is the MCX4421A-ACQN suited to?
25 GbE per port is the right tier for enterprise data, ToR access uplinks, OOB management aggregation, NVMe-oF storage initiators, and SDN/NFV virtualised servers using RoCE v2 and SR-IOV. It is NOT intended for AI training east-west fabrics — those need 200/400/800 G ConnectX-6/7 with NDR/HDR InfiniBand or Spectrum-X Ethernet.
Q. Is this a Multi-Host or socket-direct card?
No. The -ACQN suffix identifies a standard single-host OCP 2.0 mezzanine adapter. For Multi-Host (one card shared across multiple hosts) or socket-direct configurations, a different ConnectX SKU is required — please contact T.E.S to verify before ordering.
Q. What condition does T.E.S IT-SOLUTIONS supply?
This unit is supplied New, factory-sealed in original NVIDIA / Mellanox packaging, shipped from EU stock with anti-static packaging and global B2B express options. Free pre-sale compatibility advice on OCP 2.0 slot type, firmware, and Spectrum/SFP28 cabling is included.
Why buy from T.E.S IT-SOLUTIONS
T.E.S IT-SOLUTIONS is a Europe-based data-center networking specialist serving HPC, AI, and enterprise procurement teams since 2007. Every adapter is identified by MPN, ConnectX generation, ASIC sub-variant (Lx / Dx / Ex / VPI), and form factor (PCIe HHHL / FHHL / OCP 2.0 / OCP 3.0) before it ships, and every customer receives free pre-sale compatibility advice on switch, adapter, and cable pairing. Multi-currency B2B invoicing, EU stock with worldwide express logistics, and direct technical contact with our engineering team — not a call-center.