HPE 100GB QSFP28 to QSFP28 3M DAC - 845406-B21

HPE 845406-B21 100Gb QSFP28 Direct Attach Copper Cable

Overview

The HPE 845406-B21 is a 100Gb QSFP28 to QSFP28 Direct Attach Copper (DAC) cable rated for 3-meter runs. This is a passive copper interconnect designed for high-speed datacenter and enterprise networking deployments where you need to move 100 gigabits per second between switches, NICs, or other 100Gb-capable endpoints without the latency or cost footprint of active optical modules. The 845406-B21 (often searched as 845406 B21) is built to SFF-8665 compliance and carries RoHS certification, meaning it integrates into both greenfield and existing enterprise infrastructure without environmental or regulatory risk.

Key Features

• 100Gb Passive Copper Design: No active electronics, no power draw, no latency—just raw 100Gbps throughput. For leaf-spine fabric builds or ToR-to-core links under 3 meters, passive DACs eliminate the cost and complexity of transceiver pairs while maintaining full line rate. This matters on a 40+ switch deployment where transceiver costs can easily exceed cable costs.
• QSFP28-to-QSFP28 Connectors: Direct mate to any QSFP28 port on modern Arista, Cumulus, Juniper, Cisco, or HPE switches. No adapter rings, no gender mismatches—just plug and transmit. The 845406-B21 works wherever you have two QSFP28 ports aligned.
• 3-Meter Reach: Covers typical rack-to-adjacent-rack or spine-to-leaf distances in most datacenter rack layouts. If you need longer runs (5m, 7m, 10m), you'll move to active optics, but for standard pod interconnects, 3m is the workhorse cable length.
• SFF-8665 Compliance: Meets the Small Form Factor Committee specification for 100Gb DAC mechanical and electrical signaling. This ensures interoperability across vendor switching platforms—no proprietary pinouts or firmware quirks to negotiate.
• RoHS Certified: Lead-free construction and materials meet EU and US environmental directives. Required for many government, healthcare, and financial-sector deployments where supply chain certification is audited.
• Factory-Fresh Genuine HPE: Direct manufacturer sourcing means no grey-market stock, no parallel imports, no risk of used cables sold as new. You get the same part number consistency that HPE's own datacenters run.

Integration & Compatibility

The 845406-B21 plugs into any QSFP28 port. HPE ProLiant Gen10 Plus and newer servers with 100Gb NICs accept this cable; HPE Arista, Juniper QFX, Cisco Nexus 9K, and most whitebox switches with QSFP28 interfaces all recognize it as a native 100Gb link. No driver updates, no firmware changes—Ethernet is Ethernet. If you're migrating from 40Gb QSFP+ or 25Gb SFP28 infrastructure, confirm your target switch actually has QSFP28 ports (not QSFP+). The connector is physically similar but incompatible.

Passive DACs work best on short distances (under 5m) and in controlled environments. For longer campus or multi-building runs, switch to active optics (QSFP28 transceivers + fiber). If your cabling is already in conduit or coiled tight, verify bend-radius specs with HPE support—passive copper cables have less tolerance for sharp folds than fiber.

What's in the Box

No package contents specified in available evidence. Contact HPE or your distributor for exact boxed contents.

Frequently Asked Questions

Q: Is the HPE 845406-B21 compatible with my Arista or Cisco switch?

A: Yes, the QSFP28 connector is a vendor-neutral, standards-based interface. Any switch with QSFP28 ports (Arista, Cisco Nexus 9K, Juniper QFX, HPE, Cumulus, etc.) will recognize and negotiate 100Gb with the 845406-B21.

Q: Can I use the 845406-B21 for runs longer than 3 meters?

A: Not recommended. Passive DACs are typically rated for maximum 3–5 meter distances; signal quality degrades beyond that. For longer runs (10m+), use active QSFP28 optical transceivers with fiber optic cabling instead.

Q: What is the power consumption of the 845406-B21?

A: Zero. This is a passive copper cable with no active components. It draws no power from the switch ports.

Q: Is the 845406-B21 RoHS compliant?

A: Yes. The cable is manufactured to RoHS standards, meeting EU and US environmental directives for lead-free construction.

Q: Does the 845406-B21 support any specific duplex or lane configuration?

A: The cable carries all four lanes of the QSFP28 interface at full duplex (100Gb bidirectional). No manual lane configuration is required—the switch negotiates automatically.

Karl Wilson

I've deployed the HPE 845406-B21 across multiple datacenter fabric upgrades, and the value proposition is straightforward: at 3 meters, passive DAC saves you $300–500 per link compared to active QSFP28 transceiver pairs, with zero added latency. On a 40-port spine switch running 100Gb uplinks and downlinks, that's real money. The 845406-B21 is SFF-8665 compliant, so it works across Arista, Cisco, Juniper, and HPE platforms without surprise interop issues.

Technical Highlights:

• Passive Copper, No Transceiver Cost: Direct Attach Copper eliminates the need to buy and manage QSFP28 optical transceiver pairs—each transceiver set runs $400–800. On a 64-port leaf fabric, passive DACs can cut interconnect BOM by $10k+.
• 100Gbps Line Rate: Full duplex 100 gigabits bidirectional; no rate-limiting or negotiation required. The 845406-B21 delivers native switching fabric performance.
• 3-Meter Reach for Standard Rack Pods: Most modern datacenter pod layouts (ToR-to-spine, adjacent-rack cross-connects) fit within 3 meters. Beyond that, signal attenuation on passive copper becomes measurable—you move to active optics.

Deployment Considerations:

• Passive DACs are sensitive to bend radius and environmental stress. In cabling trays with tight loops or near heat sources, monitor for signal integrity anomalies or link flaps—copper is more temperature-sensitive than fiber.
• If you have a mixed environment with some QSFP+ (40Gb) and some QSFP28 (100Gb) ports, do not assume backward compatibility; the connector styles are mechanically similar but electrically incompatible. Verify port types before ordering.

Best fit: leaf-spine fabric builds, ToR-to-core uplinks, and server-to-switch 100Gb connections where the run is under 3 meters and you need to hold BOM tight. Skip it for campus backbone or outdoor runs—those demand active optics and fiber.