Home › Parts › HPE part numbers

817753-B21: HPE Ethernet 10/25Gb 2-port SFP28 640SFP28 Adapter

HPE 817753-B21 Network adapterPCIe 3.0 x825GbEStandup PCIe Card
HPENetwork adaptersPCIe 3.0 x8

Also listed as: 817755-001, 840130-001, MCX4121A-ACAT, 640SFP28, ConnectX-4-Lx · made by Mellanox

The HPE 817753-B21 (640SFP28) is a dual-port 10/25GbE SFP28 PCIe adapter built with the Mellanox ConnectX-4 Lx controller. As the early 25GbE option for HPE ProLiant Gen9 and Gen10 servers, it introduced 25Gbps per-lane networking, hardware RoCE v2, and overlay protocol offloading to enterprise compute clusters. Used buyers should test both SFP28 ports under link load and verify bracket compatibility.

Buy 817753-B21Sell yours

Specifications

Part number817753-B21
BrandHPE
Made byMellanox
TypeNetwork adapters
Other numbers817755-001, 840130-001, MCX4121A-ACAT, 640SFP28, ConnectX-4-Lx
Statusend of sale
Speed25GbE
Ports2x SFP28
InterfacePCIe 3.0 x8
Form factorStandup PCIe Card
ControllerMellanox ConnectX-4 Lx
Generation fitGen9 / Gen10 / Gen10 Plus

About the 817753-B21

The HPE 817753-B21, branded as the Ethernet 10/25Gb 2-port 640SFP28 Adapter, was HPE's introductory 25GbE PCIe card for mainstream ProLiant servers. Powered by the Mellanox ConnectX-4 Lx EN controller, it features two SFP28 ports providing 2.5x the throughput of 10GbE while using identical single-lane physical signaling. It provides hardware offloading for VXLAN, NVGRE, and GENEVE encapsulation, along with RoCE v2 for storage networking.

Compatibility

Compatible with HPE ProLiant Gen9 and Gen10 rack and tower servers, including DL380 Gen9/Gen10, DL360 Gen9/Gen10, DL560 Gen10, and ML350 Gen10. Requires an electrical PCIe 3.0 x8 or x16 slot. It has been largely succeeded on Gen10 Plus and Gen11 platforms by ConnectX-5 (P10112-B21) and Broadcom (P10115-B21) adapters, but remains common in Gen10 secondary deployments.

How to identify a genuine unit

Genuine units feature an HPE manufacturing sticker displaying Option Part Number 817753-B21, Spare Part Number 817755-001, and Assembly Part Number 840130-001. Silkscreen text on the PCB reveals Mellanox part number MCX4121A-ACAT. In operating systems using the mlx5_core driver and in iLO, it identifies as 'HPE Ethernet 10/25Gb 2-port 640SFP28 Adapter'.

Buying used

When buying second-hand 640SFP28 adapters, check the optical cages for debris and verify the presence of both standard and low-profile mounting brackets. Inspect the heatsink retention push-pins to ensure tight thermal contact with the ConnectX-4 Lx ASIC. Run firmware verification using mlxup or the HPE Service Pack for ProLiant to ensure the card's VPD data is uncorrupted.

Reference prices (last 14 days, updated 2026-10-27)

Refurbished: USD 115 (1 sighting, Oct 2026)

Used: USD 68 (1 sighting, Oct 2026)

All sightings
SellerConditionPriceNoteSeen
serversupply.comrefurbishedUSD 115Refurbished card tested with updated firmware2026-10-27
ebay.comusedUSD 68Working pull with low profile bracket2026-10-27

Prices seen on public listings on the dates shown, before tax and shipping. Not an offer.

Fits these models

Works together

How the HPE 817753-B21 connects to servers, storage and the network: 3 ways, with the hardware on each path.

iSCSI and NVMe/TCP over EthernetFile storage (NFS and SMB)Hyperconverged cluster

iSCSI and NVMe/TCP over Ethernet

Keep the speed the same at all three points: a 25GbE server, a 25GbE switch port and a 25GbE array port. Mixed speeds work but the slowest link sets the pace.

Switches

Storage

Optics

iSCSI and NVMe/TCP over Ethernet: how it fits together

File storage (NFS and SMB)

Front-end ports face the clients; back-end ports (on scale-out systems) connect the nodes to each other and need their own switch pair.

Switches

Storage

Optics

File storage (NFS and SMB): how it fits together

Hyperconverged cluster

Plan at least two 25GbE ports per node to two switches; all-NVMe clusters often move to 100GbE.

HCI nodes

Switches

Optics

Hyperconverged cluster: how it fits together

Plan and size it

Check compatibility with HPE

Before you buy, confirm the exact configuration against the vendor's own lists: firmware levels, operating systems, adapters and optics that HPE has tested with the HPE 817753-B21.

Equivalent part numbers

FAQ

What is the difference between 640SFP28 (817753-B21) and 640FLR-SFP28 (817749-B21/817751-B21)?

The 817753-B21 is a standard PCIe card, whereas the 640FLR version is a FlexibleLOM mezzanine card designed for dedicated FLR slots in Gen9/Gen10 servers.

Can 817753-B21 run with 10Gb SFP+ direct-attach copper cables?

Yes, the SFP28 ports auto-detect and support passive and active 10GbE SFP+ DAC cables as well as 10G optical transceivers.

Buying or selling 817753-B21?

New, refurbished or used. Tell us the quantity and condition and we connect you with a vetted reseller in your region, usually within one working day.

Buy 817753-B21Sell yours

Sources