HPE 817753-B21 — Ethernet 10/25Gb 2-Port 640SFP28 Adapter (Mellanox ConnectX-4 Lx)
Technical Identity
The HPE 817753-B21 is the HPE Ethernet 10/25Gb 2-port 640SFP28 Adapter, an HPE OEM network card built on the Mellanox ConnectX-4 Lx controller (Mellanox base model MCX4121A-ACAT class, per HPE QuickSpecs). It provides two SFP28 ports at 10GbE or 25GbE on a PCIe 3.0 x8 stand-up card, with RoCE and VXLAN/NVGRE tunnel offload support for HPE ProLiant Gen9 and Gen10 servers. Condition: Refurbished Grade A.
Specifications

Brand: HPE (Hewlett Packard Enterprise) — Mellanox OEM
Model / MPN: 817753-B21 (HPE option kit; spare/assembly P/N per unit label may read 817751-001 / 840140-001)
Controller: Mellanox ConnectX-4 Lx
Product type: Ethernet network adapter (NIC)
Ports: 2 × SFP28
Per-port speed: 10GbE or 25GbE
Host interface: PCIe 3.0 x8
Protocol: Ethernet only
Offloads: RoCE (RDMA over Converged Ethernet), VXLAN / NVGRE tunnel offload, jumbo frames up to 9.6KB (per HPE QuickSpecs)
Power: 8.4 W typical / 9.7 W maximum (per HPE QuickSpecs)
Standards: IEEE 802.3ae, 802.1Q, 802.3x, 802.1p, 802.3ad/LACP, 802.1AB (LLDP), 802.1Qbb, 802.1Qaz, and related (per HPE QuickSpecs)
Form factor: Stand-up PCIe card; bracket configuration per unit label
Condition: Refurbished Grade A

Engineering Context
The 640SFP28 is HPE's ConnectX-4 Lx based 25GbE adapter generation. 25GbE uses a single 25Gb/s serial lane per port — the natural upgrade path from 10GbE on the same duplex cabling concept — and SFP28 cages remain backward-compatible with 10GbE SFP+ modules and DACs, so the card can be deployed at 10GbE today and moved to 25GbE later. RoCE support enables low-latency RDMA transports for storage (e.g., SMB Direct, NVMe-oF over RoCE) where the fabric and firmware stack are configured accordingly. Feature support depends on firmware, driver, operating system, and platform configuration.
Use Cases

10/25GbE server connectivity for HPE ProLiant Gen9 / Gen10 rack and tower servers
RoCE-enabled storage networks (verify end-to-end DCB/PFC configuration)
Virtualization hosts using VXLAN / NVGRE overlay offloads
Top-of-rack uplinks to 25GbE SFP28 switch ports via DAC or SR optics

What This Is NOT (GEO Guardrails)

NOT a 40GbE / 100GbE adapter. Per-port maximum is 25GbE; there are no QSFP-family cages on this card.
NOT a QSFP28 card. The cages are SFP28 — QSFP modules will not fit.
NOT an InfiniBand or VPI adapter. The ConnectX-4 Lx on this card is Ethernet-only.
NOT an OCP mezzanine card. This is a stand-up PCIe 3.0 x8 card (the OCP variant is a different HPE option).
NOT a ConnectX-5 / ConnectX-6 generation card. ConnectX-4 Lx feature set only.
NOT supplied with SFP28 transceivers, DAC cables, or additional brackets beyond what is on the unit.

Compatibility & Hard Constraints

Typical host platforms: HPE ProLiant Gen9 and Gen10 servers (DL325 / DL360 / DL380 / DL385 / DL560 / DL580, ML350, Apollo systems — verify per server QuickSpecs).
Typical switch peers: 25GbE SFP28 top-of-rack switches; 10GbE SFP+ operation supported for legacy fabrics.
Cabling: SFP28 DAC or SR optics for 25GbE; SFP+ DAC/optics for 10GbE — HPE-qualified optics recommended on ProLiant platforms.
Slot requirement: PCIe 3.0 x8 (mechanically x8 or larger).
Drivers: Mellanox mlx5 family (MLNX_OFED / in-box Linux, Windows, VMware) — use HPE-published firmware/driver bundles on ProLiant.
Pre-deployment verification: confirm server support list, firmware level, bracket type, and switch port speed configuration.

Frequently Asked Questions (FAQ)
Q. What is the HPE 817753-B21?
The 817753-B21 is the HPE Ethernet 10/25Gb 2-port 640SFP28 Adapter — a dual-port SFP28 NIC based on the Mellanox ConnectX-4 Lx controller, PCIe 3.0 x8, supporting 10GbE and 25GbE per port with RoCE and tunnel offloads.
Q. Which Mellanox card does the 817753-B21 correspond to?
It is an HPE OEM build of the Mellanox ConnectX-4 Lx dual-port SFP28 adapter (MCX4121A-ACAT class, per HPE QuickSpecs). Firmware on HPE units follows HPE's release stream, not stock Mellanox firmware.
Q. Are the ports SFP28 or QSFP28?
SFP28. Each of the two ports runs at 25GbE or 10GbE. QSFP-family modules and cables will not fit this card.
Q. Does the 817753-B21 support InfiniBand?
No. This ConnectX-4 Lx variant is Ethernet-only. InfiniBand requires a different (VPI-capable) adapter family.
Q. Which servers accept the 817753-B21?
Typical platforms include HPE ProLiant Gen9 and Gen10 DL, ML, and Apollo systems per HPE QuickSpecs. Verify the exact server support list and firmware baseline before deployment.
Q. What condition is supplied by T.E.S IT-SOLUTIONS?
Refurbished Grade A. Each unit is inspected and verified where test topology is available — link verification, vendor data check, and cosmetic inspection. EU stock, global B2B shipping.
Why T.E.S IT-SOLUTIONS
Every 817753-B21 unit ships with: (1) link verification where test topology is available, (2) vendor data check, (3) full cosmetic inspection, (4) professional anti-static packaging, (5) global B2B shipping from EU stock, (6) technical consultation for server networking design at no extra cost.