DAC cable CBO Marconi QSFP28 to 4×SFP28, direct attach copper, 3 m

Passive direct-attach copper (DAC) cable CBO Marconi QSFP28 to 4×SFP28, 3 m, provides a fixed, low-latency copper link for short-reach high-speed connections in data centres and network racks. The cable features a single QSFP28 plug that breaks out to four SFP28 connectors, enabling a single 100Gbps QSFP28 port to connect to up to four 25Gbps SFP28 ports or compatible interfaces. The 3-metre length is suited to top-of-rack and mid-plane connections where a cost-effective, energy-efficient copper solution is preferable to optical transceivers and fibre optic cabling.

Advantages

The DAC design eliminates the need for separate transceivers and fibre patch cords, reducing component count and simplifying installation and inventory management. As a passive copper assembly it consumes no additional power for signal conversion, offering lower latency and reduced operational cost compared with active transceivers. The QSFP28-to-4×SFP28 breakout format supports flexible port consolidation and easy migration from 25GbE endpoints to 100GbE aggregation ports while maintaining predictable electrical performance over the specified 3 m span.

Suitable for

• Top-of-rack switch to server connections using 25GbE or compatible SFP28 interfaces
• Switch-to-switch mid-plane links within the same cabinet or adjacent racks
• Short-reach aggregation links in data centre spine-and-leaf architectures
• Environments where fixed-length, low-latency copper links reduce total cost of ownership

Key specifications

• Connector type: QSFP28 (one end) to 4×SFP28 (breakout)
• Cable type: Passive direct-attach copper (DAC)
• Length: 3 metres
• Supported data rates: 25GbE per SFP28 channel; aggregated support for 100GbE via QSFP28
• Use case range: Short-reach, within-rack and adjacent-rack connections
• Latency: Low, passive electrical connection (no signal conversion required)

How to use

Insert the QSFP28 plug into the QSFP28 port on the aggregation device and connect each SFP28 plug into the corresponding SFP28 ports on the target devices. Ensure both ends are fully seated and that port settings (speed, lane mapping, and MTU) on connected switches and servers are configured to match the chosen interface rates (for example, 25GbE per SFP28 lane or 100GbE on the QSFP28). Verify link status through device management interfaces and check for any vendor-specific compatibility notes if equipment from different manufacturers is used.

Recommendations

Use this passive DAC for short, within-rack and adjacent-rack connections where low latency and cost efficiency are priorities. Avoid bending the cable sharply; follow standard minimum bend radius guidance and keep the assembly away from sources of mechanical strain or excessive heat. For longer runs or where optical isolation is required, consider optical transceivers and fibre cabling instead.