Arista Networks CAB-D-8S-400G-0.5M Compatible 400G QSFP-DD 8 x 50G PAM4 to 8 x 50G SFP56 50G PAM4 Passive Copper Breakout Cable, 0.5m (2ft)

Product Highlights

• Compatible alternative to Arista Networks CAB-D-8S-400G-0.5M
• 400G connectivity at 400Gbps
• Interface configuration: QSFP-DD to 8x SFP56
• Fixed length and part number: 0.5m (2ft), CAB-D-8S-400G-0.5M
• Cable construction: Passive Breakout DAC
• Conductor specification: 30AWG
• Maximum power consumption: 0.1W (QSFP-DD End)0.1W (SFP56 Per End)
• Minimum bend radius: 33.5mm

Specifications

Signal and Lane Configuration

The listed modulation format is QSFP-DD-8x 50G-PAM4SFP56-50G-PAM4. Both host interfaces must be configured for the same aggregate rate and lane arrangement. A connector that fits mechanically does not by itself guarantee that the remote port supports this encoding or breakout mode.

Power and Thermal Planning

The rated power consumption is 0.1W (QSFP-DD End)0.1W (SFP56 Per End). Include this load in the host-port power and thermal budget, especially in densely populated switches. Maintain front-panel clearance and do not bundle the cable so tightly that it obstructs airflow around the connectors.

Cable Construction and Routing

This assembly uses 30AWG conductors, PVC (OFNR) jacket, minimum bend radius 33.5mm. These mechanical characteristics affect how the cable should be dressed behind the equipment. Avoid sharp edges, excessive ties and repeated tight bends close to the connector boots.

Network and Protocol Considerations

The intended application is determined by the host interface and protocol support. Listed interface and protocol references include QSFP-DD MSA, SFF-8432, IEEE 802.3bs-400GAUI-8, IEEE802.3cd-50GAUI-1, CMIS 4.0, SFF-8472. Confirm that the host firmware and port configuration support the same operating mode.

Breakout Port Mapping

The QSFP-DD to 8x SFP56 configuration divides the high-speed interface into multiple lower-speed connections. Verify the upstream lane assignment, downstream port speeds and breakout setting on the host before connecting the assembly. Each branch must attach to the correct remote interface.

Passive Copper Operation

A passive DAC has no separate optical conversion stage. Its low-power, low-latency operation is useful for short equipment links, but the assembly must remain within the length and signaling mode accepted by both hosts.

Length Selection and Installation Planning

The 0.5m (2ft) length is suited to closely aligned ports where excessive slack would obstruct airflow or complicate dressing. Measure the actual port-to-port path before choosing CAB-D-8S-400G-0.5M; even a short assembly must retain the specified bend radius and should never be pulled tight behind the equipment.

Position Within the Length Range

CAB-D-8S-400G-0.5M is the shortest of 6 verified length options in this family. It is the preferred choice when the port positions are close and cable slack must be kept to a minimum. The next option is CAB-D-8S-400G-1M at 1m (3ft), adding 0.5m for a less direct routing path; selecting it unnecessarily would leave more cable to dress.

Procurement and Port-Mapping Review

A useful purchase order should identify the host platform, the expected OEM code and the exact cable length as separate pieces of information. This prevents a physically similar assembly from being substituted when the port identification or reach is different. For mixed-length installations, prepare one order line per part number and reconcile each delivered cable with its intended pair of ports. For this assembly, the listed conductor specification is 30AWG; the minimum bend radius is 33.5mm; the stated power consumption is 0.1W (QSFP-DD End)0.1W (SFP56 Per End); the jacket material is PVC (OFNR).

Arista Networks Compatibility and Factory Testing

Our procurement-oriented compatibility check begins with the OEM reference and ends with a live host link. We record the physical length separately from the identification configuration, so the cable supplied for this page remains the stated version rather than a generic length substitute. Where supported by the host, link stability and diagnostic indications are reviewed together with the established link.

Ordering Information

For a clear bill of materials, quote the OEM reference, HT part number, length and quantity on the same line. Add the switch or server model and software release when a pre-order review is required; project labels can repeat those details for receiving and installation teams. This page’s fixed configuration is 0.5m (2ft); another length must be quoted under its corresponding part number.

Quality Assurance and Packaging

Before packing, the assembly is checked for connector condition, identification and link operation. Cables for multi-line orders can be labelled and grouped by part number, making it easier to match each length to the procurement record without opening every protective bag. Standard protective packing is used by default, with project documentation arranged when requested.

Frequently Asked Questions

Shipping and Lead Time

Standard configurations normally ship within one to three working days, while production quantities are confirmed with the order. Worldwide courier services are available, with air or sea freight for consolidated shipments; freight-collect delivery and coordination with a customer’s logistics provider can be arranged.