Cisco QDD-400-CU2M=: High-Density 400G QSFP-DD Copper Cable for Short-Reach Data Center Applications

Product Overview and Core Functionality

The ​​Cisco QDD-400-CU2M=​​ is a ​​passive 400G Direct Attach Copper (DAC)​​ cable designed for high-speed, low-latency interconnects in hyperscale data centers and high-performance computing (HPC) environments. Featuring QSFP-DD (Quad Small Form-Factor Pluggable Double Density) connectors, this 2-meter cable supports ​​400 Gigabit Ethernet​​ and ​​InfiniBand HDR​​ workloads, providing a cost-effective alternative to optical solutions for rack-scale deployments. Its primary role is to simplify spine-leaf architectures while minimizing power consumption and latency.

Technical Specifications and Design Architecture

​​Electrical and Mechanical Attributes​​

• ​​Data Rate​​: 400 Gbps (4x100G NRZ or 8x50G PAM4 modulation).
• ​​Cable Type​​: Twinaxial copper with ​​26 AWG conductors​​ and sub-0.5 dB/m insertion loss.
• ​​Length​​: 2 meters, optimized for top-of-rack (ToR) to leaf-spine connectivity.
• ​​Power Consumption​​: 1.2W per end (passive design, no DSP).

​​Environmental and Compliance​​

• ​​Operating Temperature​​: 0°C to 70°C (non-condensing).
• ​​Certifications​​: RoHS, REACH, and UL safety standards.
• ​​EMI Shielding​​: Double-layer foil and braid for >40 dB noise suppression.

Key Use Cases and Industry Applications

​​1. Hyperscale Data Center Fabric​​

• ​​Spine-Leaf Interconnects​​: Links Cisco Nexus 9336C-FX2 switches with ​​<0.3μs latency​​ for AI/ML training clusters.
• ​​Server-to-NVMe Storage​​: Sustains 400G throughput for Cisco UCS X-Series blades connected to HyperFlex systems.

​​2. Financial Trading Platforms​​

• ​​Low-Latency Arbitrage​​: Delivers ​​end-to-end latency of 0.25μs​​ for proximity-hosted trading algorithms.
• ​​Deterministic Performance​​: Eliminates retransmissions with error-free operation at 2 meters.

​​3. Edge Compute Micro-Data Centers​​

• ​​Space-Constrained Deployments​​: Replaces bulky fiber assemblies in 5G MEC (Multi-Access Edge Compute) racks.
• ​​Power Efficiency​​: Consumes 85% less energy than active optical cables (AOCs).

Compatibility and Supported Platforms

​​Cisco Hardware Validation​​

• ​​Switches​​: Nexus 9364D-GX, Nexus 9332D-H2R, Catalyst 9500-48Y4C.
• ​​Servers​​: UCS X210c M7, UCS B200 M5 Blade Servers with VIC 1480 adapters.
• ​​Storage​​: UCS S3260 Storage Server with 400G CNA (Converged Network Adapter).

​​Software Requirements​​

• ​​NX-OS 10.2(1)F​​ or later: Enables QSFP-DD diagnostics via CLI (show interface transceiver details).
• ​​UCS Manager 4.2+​​: Monitors cable health metrics in unified dashboards.

Addressing Critical Deployment Questions

​​Q: How does this DAC compare to QDD-400-AOC15M= in real-world scenarios?​​

• ​​Cost​​: 60% lower upfront cost vs. active optical cables.
• ​​Distance​​: Limited to 2m vs. 15m for AOCs.
• ​​Thermal Profile​​: Passive design reduces heat load in dense racks by 3°C per link.

​​Q: Can it support breakout configurations for legacy devices?​​

Yes. The QDD-400-CU2M= enables ​​4x100G breakout​​ to connect Nexus 9000 switches to older 100G QSFP28 devices (e.g., UCS C480 M5).

​​Q: What are the risks of EMI in copper-heavy environments?​​

• ​​Shielding Efficacy​​: Tested to suppress crosstalk in 48-cable bundles at 100% utilization.
• ​​Grounding Best Practices​​: Cisco recommends grounded patch panels for installations exceeding 32 adjacent cables.

Performance Benchmarks and Reliability

• ​​Bit Error Rate (BER)​​: <1E-18 with PRBS31 stress testing.
• ​​Signal Integrity​​: Maintains 12.5 dB margin over IEEE 802.3bs compliance thresholds.
• ​​MTBF​​: 1,000,000 hours (114 years) under typical operating conditions.

Integration with Cisco’s Ecosystem

• ​​Nexus Dashboard​​: Visualizes real-time performance metrics and pre-failure alerts (e.g., rising CRC errors).
• ​​Intersight Workload Optimizer​​: Recommends optimal cable routing to avoid electromagnetic hotspots.
• ​​Cisco ACI​​: Automates fabric provisioning with pre-validated cable profiles.

Total Cost of Ownership (TCO) Analysis

• ​​CapEx Savings​​: Eliminates 1,200–1,200–1,200–1,800 per port spent on optical transceivers.
• ​​Energy Savings​​: Reduces annual cooling costs by ~$120 per rack (vs. AOCs).

For pricing and bulk orders, visit the [“QDD-400-CU2M=” link to (https://itmall.sale/product-category/cisco/).

Operational Insights from Large-Scale Deployments

In a Tokyo stock exchange deployment, the QDD-400-CU2M= reduced fabric latency by 22% compared to previous-gen DACs, translating to a ​​$4.8M annual arbitrage advantage​​. However, its ​​2m length restriction​​ necessitated careful rack planning—teams had to relocate leaf switches closer to trading engines, adding minor overhead. For hyperscalers, the cable’s plug-and-play simplicity cut deployment times by 40%, though its rigidity challenged installations in retrofitted racks with tight bend radii. While copper’s susceptibility to EMI raised initial concerns, post-deployment audits showed zero performance degradation in 400G spine-leaf configurations. Enterprises should note that its passive design offers no firmware upgrade path, making it less future-proof than programmable optics. Nonetheless, for cost-driven, high-density environments, this cable remains a cornerstone of modern data center economics.