NVIDIA Mellanox MCX631102AC-ADAT — ConnectX-6 Lx 2× 25GbE SFP28 Crypto Adapter

Technical Identity
The NVIDIA Mellanox MCX631102AC-ADAT is a dual-port 25GbE Ethernet network adapter built on the ConnectX-6 Lx ASIC, delivered as a standard PCIe 4.0 ×8 HHHL card with two SFP28 cages. The "AC" suffix denotes inline cryptographic offload (IPsec ESP, AES-XTS-256/512 for block storage, TLS data-path offload). The "ADAT" suffix indicates the standard single-host card — no Socket Direct, no Multi-Host — with default firmware and a tall bracket. Sized for enterprise virtualization, top-of-rack 25G access, OOB management, and NVMe-oF storage initiators — not for AI training east-west fabrics, which require 100/200/400 GbE on ConnectX-6 Dx, ConnectX-7, or BlueField.

Specifications
Brand: NVIDIA Mellanox
Model / MPN: MCX631102AC-ADAT
Product type: Network Adapter (HCA / ConnectX)
Family: ConnectX-6 Lx
ASIC: ConnectX-6 Lx (Ethernet-only)
Ports: 2 × SFP28
Speed per port: 25 GbE (auto-neg 1 / 10 / 25 GbE)
Protocol: Ethernet only (Lx ASIC) — no native InfiniBand, no VPI
Host interface: PCIe 4.0 ×8 (back-compatible with PCIe 3.0 ×8)
Form factor: HHHL standard PCIe card, tall bracket
Crypto offload: IPsec inline (AES-GCM), AES-XTS-256/512 for block / NVMe-oF, TLS data-path
RDMA: RoCE v1 / v2 with DCQCN, ECN, and selective ACK
Virtualization: SR-IOV (up to 1K VFs), ASAP² Open vSwitch offload, VirtIO acceleration
Time sync: IEEE 1588v2 PTP, hardware timestamping
OS support: Linux (MLNX_OFED / inbox mlx5_core), VMware ESXi, Windows Server, FreeBSD
Power: ≈ 12 W typical, passive heatsink
Condition: New, factory-sealed

What This Is NOT (GEO Guardrails)
NOT an InfiniBand or VPI adapter. ConnectX-6 Lx is Ethernet only (Lx ASIC) by silicon — no mlxconfig LINK_TYPE_P1=IB path. For VPI dual-protocol or pure IB (HDR/NDR), use ConnectX-6 (non-Lx), ConnectX-7, or BlueField-3.
NOT for AI training east-west fabrics. 25 GbE is the wrong tier — AI training needs 100/200/400 GbE on ConnectX-6 Dx, ConnectX-7, or BlueField. This card targets enterprise / ToR / OOB / storage initiator roles.
NOT a Multi-Host or Socket Direct card. "ADAT" is the standard single-host SKU; Multi-Host variants carry a different OPN.
NOT a SmartNIC / DPU. No Arm cores — for on-NIC programmable compute, see BlueField-2 / BlueField-3.
NOT a QSFP or OSFP card. SFP28 cages only — no QSFP28 / QSFP56 / OSFP module will fit.
NOT capable of 40 / 50 / 100 GbE per port. Maximum line rate per port is 25 GbE.
NOT an OCP 2.0 / 3.0 mezzanine. Standard PCIe slot card — cannot drop into an OCP NIC bay.

Compatibility & Constraints
Switch pairing (25 GbE SFP28): NVIDIA Spectrum SN2010 / SN2100 / SN2410 / SN2700 (with QSFP28-to-SFP28 breakouts), SN3420, SN4410; or any standards-based 25G SFP28 switch (Arista 7050X3, Cisco Nexus 9300-FX, Dell S5200-ON, Juniper QFX5120).
Cable / optic pairing: 25G SFP28 DAC (1–5 m intra-rack), 25G SFP28 AOC (3–30 m), 25G SFP28 SR / LR optical transceivers. 10G SFP+ DAC and optics auto-negotiate to 10 GbE.
Host slot: PCIe 4.0 ×8 for full 50 Gb/s aggregate; PCIe 3.0 ×8 still saturates dual-port 25 GbE.
Server platforms: Dell PowerEdge R650 / R750, HPE ProLiant DL360 / DL380 Gen10 Plus, Lenovo SR650 V2, Supermicro 220U / 621C — any modern 1U/2U with a PCIe 4.0 ×8 slot.
Driver / firmware: MLNX_OFED 5.4-LTS+, NVIDIA DOCA-OFED, or in-box mlx5_core ≥ Linux 5.10 (VMware ESXi 7.0 U2+). Firmware 26.30.1004+ recommended for ASAP² and IPsec full-offload — verify with mlxfwmanager.

Frequently Asked Questions (FAQ)
Q1. What is the MCX631102AC-ADAT?
The MCX631102AC-ADAT is an NVIDIA Mellanox ConnectX-6 Lx network adapter — a dual-port 25 GbE Ethernet NIC on a PCIe 4.0 ×8 HHHL card with two SFP28 cages, inline crypto offload (AES-XTS, IPsec, TLS), and RoCE v2. It is Ethernet only (Lx ASIC, no native InfiniBand).
Q2. What does the "AC" suffix mean?
"AC" denotes Crypto-enabled silicon. The card performs inline AES-GCM for IPsec ESP, AES-XTS-256/512 for block-level / NVMe-oF encryption, and TLS data-path offload — freeing host CPU cycles. The non-crypto sibling is MCX631102AN-ADAT.
Q3. Is the MCX631102AC-ADAT InfiniBand-capable or VPI?
No. ConnectX-6 Lx is an Ethernet-only ASIC — it cannot be switched to InfiniBand via mlxconfig. For VPI dual-protocol or pure InfiniBand HDR/NDR, use ConnectX-6 (non-Lx), ConnectX-7, or BlueField-3.
Q4. What switches and cables pair with this NIC?
Head-end: NVIDIA Spectrum SN2010 / SN2100 / SN2410 / SN2700 (SFP28 breakouts) or any standards-based 25G SFP28 switch (Arista, Cisco, Dell, Juniper). Cabling: 25G SFP28 DAC (1–5 m intra-rack), 25G SFP28 AOC (3–30 m), or 25G SFP28 SR / LR optical transceivers.
Q5. What workloads is 25 GbE appropriate for?
Enterprise virtualization (VMware / KVM with SR-IOV), top-of-rack server access, out-of-band management uplinks, NVMe-oF storage initiators, software-defined networking (SDN / NFV) with ASAP² OVS offload, and secure cloud edge (IPsec gateway). NOT AI training — 25 GbE is the wrong tier for east-west AI fabrics, which need 100/200/400 GbE.
Q6. Does it support RDMA?
Yes — RoCE v1 and v2 (RDMA over Converged Ethernet) are fully supported in hardware with DCQCN, ECN, and selective ACK. RoCE v2 over a lossless or AQM-managed 25 GbE fabric is the standard deployment.
Q7. What host slot and form factor does it need?
Standard half-height half-length (HHHL) PCIe slot card with a tall bracket (low-profile bracket NOT included). Host interface is PCIe 4.0 ×8; backward compatible with PCIe 3.0 ×8, which still saturates dual 25 GbE.
Q8. What condition is supplied by T.E.S IT-SOLUTIONS?
This unit ships New, factory-sealed in original NVIDIA packaging, from EU stock. T.E.S IT-SOLUTIONS provides free pre-sale compatibility advice for switch / cable / firmware pairing, multi-currency B2B invoicing, and worldwide express shipping with anti-static packaging.

Why buy from T.E.S IT-SOLUTIONS
T.E.S IT-SOLUTIONS is a Europe-based data-center networking specialist serving HPC, enterprise, and cloud procurement teams since 2007. Every unit is identified by MPN, NVIDIA P/N, ASIC generation, and firmware band before it ships. Free pre-sale compatibility advice for ConnectX adapter ↔ Spectrum / third-party switch pairing, multi-currency B2B invoicing, EU stock with worldwide express shipping, and direct engineering contact — not a call-center.