HP 655874-B21 QSFP/SFP+ Adaptor Kit — main product image

HP 655874-B21 QSFP/SFP+ Adaptor Kit

Name: HP 655874-B21 QSFP/SFP+ Adaptor Kit
Brand: HP
SKU: 655874-B21

The HP 655874-B21 adapter kit bridges QSFP and SFP+ interfaces, letting existing 40GbE infrastructure share ports with 10GbE SFP+ modules without additional switching hardware.

$50.00*

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*Price sourced from Amazon.com. Last updated:Jun 04, 2026.Price and availability are subject to change.

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Overview

The HP 655874-B21 QSFP/SFP+ Adaptor Kit solves a specific interoperability problem in HP networking environments: QSFP ports designed for 40GbE operation are physically incompatible with the smaller SFP+ form factor used by 10GbE transceivers. This adapter bridges that gap, allowing an SFP+ module to be inserted into a QSFP-native port on a compatible HP switch or server adapter. The engineering trade-off is explicit — the QSFP port drops from 40GbE to 10GbE operation when this adapter is installed, consuming one of the QSFP interface's four bonded lanes. For network architects managing mixed-speed environments where some endpoints require SFP+ connectivity and others need full 40GbE throughput, this adapter provides the flexibility to use a single switching platform without deploying separate 10GbE switching hardware.

The real-world deployment scenario is typically a data center or server room where HP 40GbE top-of-rack switches serve both high-throughput server-to-server links (using native QSFP/DAC cables) and lower-bandwidth SFP+ device connections via this adapter. HP's OEM part numbering matters here: HP networking firmware on ProCurve/Aruba switches and ProLiant server adapters performs transceiver and adapter validation — using HP-validated components is the reliable path to avoiding "unsupported transceiver" warnings that can affect link stability on some firmware versions. This is a targeted, fit-for-purpose component, not a universal solution — evaluate it specifically against your HP platform model and firmware version before procurement.

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Specifications

Brand

Part Number

655874-B21

Type

QSFP to SFP+ Adaptor Kit

Function

Enables SFP+ transceiver use in QSFP ports

Compatible Platforms

HP ProCurve/Aruba, HP ProLiant (verify model compatibility)

Pros & Cons

👍 Pros

Enables SFP+ modules to occupy QSFP ports — allowing 10GbE devices to coexist on 40GbE-only switching infrastructure without adding separate line cards
HP OEM part number 655874-B21 ensures firmware recognition on HP ProCurve/Aruba and ProLiant platforms that enforce vendor compatibility checks
Eliminates the need for a separate 10GbE SFP+ switch for low-density deployments where only a few SFP+ connections are required
Standard QSFP-to-SFP+ form factor allows standardized installation procedures already familiar to HP network engineers
Single-adapter solution reduces cabling complexity by utilizing existing QSFP port infrastructure for mixed-speed environments

👎 Cons

Reduces a QSFP 40GbE port to 10GbE operation — the remaining three 10GbE lanes of the QSFP interface are sacrificed per adapter installed
HP firmware on some platforms may reject non-HP SFP+ transceivers inserted through this adapter, restricting transceiver sourcing options
Use case is narrow — only relevant for HP-platform deployments needing QSFP-to-SFP+ bridging; not a general-purpose networking component
Product listing contains no technical specifications or installation documentation — HP's official platform compatibility matrix must be consulted independently
Not compatible with QSFP+ (40GbE) to QSFP28 (100GbE) transitions — this adapter operates exclusively within the 10GbE SFP+ tier

Frequently Asked Questions

What does this adapter kit physically do — what connector converts to what?

The HP 655874-B21 is a QSFP-to-SFP+ adapter kit. It allows an SFP+ transceiver (10GbE) to be inserted into a QSFP (40GbE) port on a compatible HP switch or network card. This enables mixed-speed deployments on hardware with only QSFP ports, without requiring a dedicated SFP+ port card.

Which HP platforms and switches is the 655874-B21 validated for?

This part number is an HP OEM component validated for HP ProCurve/Aruba and ProLiant server adapters that have QSFP ports. Compatibility is specific to HP's validated hardware list — third-party switches that accept generic QSFP-to-SFP+ adapters may or may not recognize this HP-specific module. Verify against your specific switch or adapter model number.

Does using this adapter reduce bandwidth on the QSFP port to 10GbE?

Yes. A QSFP port operates at 40GbE by bonding four 10GbE lanes. When an SFP+ adapter is inserted, the port operates at 10GbE — one of those four lanes is used, and the remaining bandwidth is unused. This is a deliberate trade-off when you need SFP+ compatibility over full 40GbE throughput.

Can this adapter be used with non-HP SFP+ transceivers?

HP networking hardware commonly enforces transceiver compatibility checks in firmware — non-HP SFP+ modules inserted via this adapter may generate warnings or be blocked depending on the host platform and firmware version. HP-branded or HPE SmartBuy SFP+ transceivers are the validated pairing.

Is this adapter hot-swappable?

In supported HP platforms, SFP/QSFP adapters are generally hot-swappable in line with the host port's hot-swap capability. Verify the specific host switch or adapter documentation — some platforms require a link-down event or port toggle after insertion for the module to be recognized.