HPE 100GB QSFP28 to 4X25GB SFP28 3M DAC - 845416-B21

HPE 845416-B21 100GB QSFP28 to 4x25GB SFP28 Direct Attach Copper Cable

Overview

The HPE 845416-B21 is a 100Gb QSFP28 to 4x25Gb SFP28 direct attach copper (DAC) cable engineered for high-density data center and enterprise switching environments. This 3-meter cable enables you to split a single 100Gb QSFP28 port into four independent 25Gb SFP28 connections — a critical requirement when consolidating bandwidth across multiple 25Gb-capable switch ports or network interface cards without introducing the latency and power overhead of active optics.

Key Features

• 100Gb to 4x25Gb lane splitting: One QSFP28 connector on the source side terminates to four individual SFP28 connectors on the end side. This avoids the need for breakout switches or intermediate active components, reducing points of failure and complexity in your physical interconnect layer.
• Direct Attach Copper (DAC) technology: Passive copper implementation means no power consumption, no active electronics to manage or debug, and zero latency introduction. Ideal for top-of-rack (ToR) aggregation and inter-switch connections in low-latency architectures.
• 3-meter cable length: Sufficient reach for standard rack-to-adjacent-rack deployments (approximately 10 feet), covering typical east-west traffic patterns in modular data center layouts without requiring longer runs that introduce signal degradation.
• SFF-8665 compliance: Adheres to the Small Form Factor Committee specification for QSFP28 multi-lane breakout, ensuring interoperability with industry-standard equipment and eliminating proprietary connector lock-in.
• RoHS-compliant construction: Lead-free solder and compliant materials simplify procurement for regulated environments and reduce environmental impact without performance tradeoffs in copper-based signal delivery.
• Factory-new genuine HPE sourcing: Direct manufacturer supply chain eliminates grey-market risk and ensures consistent electrical performance across all four SFP28 lanes.

Integration & Compatibility

The 845416-B21 works with any HPE or third-party switch, NVR, or network appliance that provides a QSFP28 port capable of 100Gb operation and four corresponding 25Gb SFP28 ports on the receiving end. This includes HPE Arista, Mellanox, and Cisco platforms that support 25Gb lane speed negotiation. Verify your hardware documentation for QSFP28 breakout support before deployment — not all 100Gb ports natively support active lane splitting. Because this is a passive DAC, no firmware or driver updates are required; the cable negotiates speed automatically once both endpoints are seated.

The cable's copper construction performs best over the 3-meter run; longer distances or difficult cable routing may require active optical breakout cables instead. In dense patch-panel environments, confirm that your SFP28 module spacing accommodates four adjacent connectors — some compact form factors leave limited room between transceiver slots.

Frequently Asked Questions

Q: Does the 845416-B21 require driver or firmware installation?

A: No. Direct attach copper cables are passive devices with no electronics. Once both connectors are firmly seated, speed negotiation happens automatically at the port level. Verify QSFP28 breakout mode is enabled in your switch CLI if the ports do not auto-detect.

Q: What is the maximum cable distance for the 845416-B21?

A: The 3-meter specification is the qualified operating length. Copper DAC performance degrades beyond this distance due to impedance mismatch and signal attenuation. For runs longer than 3 meters, use active optical breakout cables (AOCs) instead.

Q: Is the 845416-B21 compatible with non-HPE equipment?

A: Yes. The cable adheres to SFF-8665 (QSFP28 MSA) and industry-standard pinout. It will work with any QSFP28 and SFP28 transceiver that supports 100Gb and 25Gb speeds, including Arista, Mellanox, Cisco, and Juniper platforms. Always confirm your switch or adapter supports passive breakout mode.

Q: How do I know if my switch supports QSFP28 breakout?

A: Check your switch datasheet for "QSFP28 breakout mode" or "lane splitting" support. Most modern high-density switches (48-port and larger) include this. Enter your switch model into your vendor's CLI reference and search for "breakout" or "4x25G." If your hardware doesn't list breakout capability, you'll need an active breakout switch or optics instead.

Q: Can I use the 845416-B21 in a surveillance network recorder (NVR) with multiple 25Gb uplink ports?

A: Yes, if your NVR or switch fabric has a QSFP28 port and supports passive breakout mode. This is common in high-end video recorders and aggregation switches where multiple 25Gb lanes increase inter-recorder replication or uplink bandwidth. Confirm your specific NVR model documentation lists QSFP28 breakout support.

Ted Perry

The HPE 845416-B21 solves a real problem in high-speed network architecture: you've got a QSFP28 100Gb uplink, but your downstream equipment (or your recorder infrastructure) speaks 25Gb SFP28. Rather than burning two active transceiver slots and introducing power draw and latency, this passive DAC lets you split one port into four discrete 25Gb lanes with zero active components.

Technical Highlights:

• 100Gb QSFP28 to 4x25Gb SFP28 lane splitting: Single passive connection replaces what would otherwise require active breakout optics — saving ~6–8W per breakout and eliminating a point of management complexity. Copper DAC also means no transceiver cooling load in dense deployments.
• SFF-8665 compliance: Standards-based pinout guarantees compatibility across vendor platforms (Arista, Mellanox, Cisco, HPE). No proprietary lock-in and no surprise incompatibilities when you're integrating multi-vendor fabric.
• 3-meter passive reach: Qualified copper distance covers typical ToR-to-adjacent-rack topologies. Any longer run requires active optics — so plan your physical layout around this boundary or budget for AOCs on longer runs.

Deployment Considerations:

• Not all QSFP28 ports support breakout mode — verify your switch or NVR documentation explicitly lists "QSFP28 breakout" or "4x25G mode" before purchasing. Some hardware ships with this disabled by default and requires CLI enablement.
• The four SFP28 connectors on the tail side occupy physical space — dense patch panels with tight port spacing may force you into awkward cable routing. Test fit before mass deployment.

This cable belongs in high-speed NVR aggregation fabrics, data center spine-leaf topologies, and any environment where you're consolidating 100Gb backbone into distributed 25Gb endpoints. If your recorder or switch can't do breakout, you'll regret buying this — confirm first.