Cisco QDD-400-CU1M
400G Passive Cable, 1m, Original Cisco
Product Highlights
As data centers scale to 400G and beyond, the cabling between switches, routers, and servers inside the rack must keep pace — without inflating power budgets or adding optical complexity. The Cisco QDD-400-CU1M is a genuine Cisco 400G passive copper direct attach cable (DAC) that delivers 400 Gbps of bandwidth over a 1-meter twinax copper assembly using the QSFP-DD form factor.
Designed for short-reach, point-to-point 400 Gigabit Ethernet links, this cable eliminates the need for separate transceiver modules and fiber patch cords. It connects two QSFP-DD ports directly, providing a low-latency, low-power, and cost-effective interconnect for top-of-rack and adjacent-rack deployments. The cable implements eight independent 50 Gbps PAM4 electrical lanes compliant with IEEE 802.3cd 400GBASE-CR8 and the 400GAUI-8 host interface standard.
With a maximum power consumption of just 1.5 W per end and full compliance with the QSFP-DD MSA CMIS Rev4.1, the QDD-400-CU1M is purpose-built for high-density data center environments where every watt and every rack unit counts. It is hot-swappable and suitable for data centers, enterprise core and distribution layers, high-performance computing networks, and service provider applications.
Features & Benefits
400G Passive Copper Direct Attach
The QDD-400-CU1M provides a QSFP-DD-to-QSFP-DD copper direct-attach solution that eliminates the cost and complexity of separate optics and fiber patch cords. As a passive cable, it draws minimal power (≤1.5 W per end) and introduces near-zero latency — ideal for latency-sensitive workloads such as high-frequency trading, HPC clusters, and storage fabrics.
QSFP-DD Double-Density Form Factor
Built on the QSFP-DD (Quad Small Form-Factor Pluggable Double Density) standard, this cable doubles the electrical lane count from four to eight compared to QSFP28, enabling 400G in the same port footprint. The hot-swappable design allows field replacement without powering down the host device, minimizing maintenance windows.
Standards-Based Interoperability
The cable is compliant with IEEE 802.3cd 400GBASE-CR8, the QSFP-DD MSA CMIS Rev4.1, and OIF CEI-56G-VSR-PAM4 electrical specifications. This broad standards compliance ensures reliable interoperability across Cisco platforms with QSFP-DD 400G ports and simplifies qualification in multi-vendor environments.
Cost-Effective Intra-Rack Connectivity
Passive copper DACs are significantly less expensive than optical transceiver-plus-fiber combinations for short-reach links. The QDD-400-CU1M is purpose-built for within-rack and adjacent-rack connections up to 1 meter, offering a cost-effective way to establish 400-Gigabit links between QSFP-DD ports on Cisco switches and routers.
Deployment Scenarios
Data Center Top-of-Rack Interconnects
Connect 400G-capable leaf switches to servers, storage nodes, or adjacent spine switches within the same rack or cabinet. The 1-meter passive copper cable delivers maximum throughput with minimal latency and zero optical power overhead — perfect for dense leaf-spine fabrics.
High-Performance Computing (HPC) Clusters
Link compute nodes and GPU servers at 400 Gbps for AI/ML training workloads and parallel computing jobs. The passive copper design ensures deterministic, ultra-low-latency data transfer critical to tightly coupled HPC applications.
Enterprise Core and Distribution Layers
Establish high-bandwidth 400G uplinks between core and distribution switches in campus or enterprise data center environments. The genuine Cisco cable ensures plug-and-play compatibility and simplified procurement for organizations standardized on Cisco infrastructure.
Service Provider Infrastructure
Deploy cost-effective 400G links between routers and switches in service provider points of presence (PoPs) or central offices where short-reach copper connectivity reduces both capital and operational expenditure.
General
Performance
Physical
Power
Environmental
Compliance
Compatibility Notes
The Cisco QDD-400-CU1M is supported on Cisco platforms equipped with QSFP-DD 400G ports, including the Cisco Nexus 9316D-GX and Cisco N3432D-S. Always consult the Cisco Transceiver Module Group (TMG) Compatibility Matrix for the latest platform and software compatibility information before ordering.
Downloads & Resources
Frequently Asked Questions
| Part Number | Product | Key Difference |
|---|---|---|
| QDD-400-CU2M | Cisco 400G QSFP-DD Passive Copper Cable, 2m | Same passive DAC technology but with 2-meter reach for slightly longer intra-rack or adjacent-rack runs. |
| QDD-400-CU2.5M | Cisco 400G QSFP-DD Passive Copper Cable, 2.5m | Extended 2.5-meter reach for cross-rack connections where 1m is insufficient. |
| QDD-400-CU0.5M | Cisco 400G QSFP-DD Passive Copper Cable, 0.5m | Shorter 0.5-meter cable for ultra-short same-shelf connections with tighter cable management. |
| QDD-400-AOC3M | Cisco 400G QSFP-DD Active Optical Cable, 3m | Active optical cable for longer reaches beyond passive copper limits; thinner and lighter for improved airflow. |