Cisco NXA-QDD-2Q-CU1M=: QSFP-DD Passive Copper Cable for 400G/800G Data Center Fabric Scalability

​​Product Overview and Design Objectives​​

The ​​Cisco NXA-QDD-2Q-CU1M=​​ is a ​​QSFP-DD (Quad Small Form-Factor Pluggable Double Density)​​ passive direct-attach copper (DAC) cable designed for ​​high-density 400G/800G interconnects​​ in modern data centers. Optimized for ​​Nexus 9000 Series switches​​ like the ​​9336C-FX2​​ and ​​93600CD-GX​​, this 1-meter cable enables cost-effective, low-latency connectivity between leaf-spine tiers or adjacent racks. Key design goals include:

• ​​Density Maximization​​: Supports ​​36x400G ports per 1RU​​ in Nexus 9336C-FX2 chassis via ​​QSFP-DD-to-QSFP-DD​​ configurations.
• ​​Power Efficiency​​: Consumes ​​0.1W per port​​ (vs. 1.5W for active optical cables), reducing annual cooling costs by ​​$120/rack​​.
• ​​Backward Compatibility​​: Works with ​​QSFP28 (100G)​​ and ​​QSFP56 (200G)​​ ports using breakout adapters, preserving legacy infrastructure investments.

The cable complies with ​​IEEE 802.3bs​​ and ​​QSFP-DD MSA​​ standards, ensuring interoperability in multi-vendor environments.

​​Technical Specifications and Performance Validation​​

Cisco’s 2024 Data Center Cabling Guide confirms the following metrics:

• ​​Data Rate​​: ​​2x200G​​ (400G aggregate) via ​​PAM4 modulation​​ and ​​50 Gbaud signaling​​.
• ​​Insertion Loss​​: ​​<16 dB at 26.56 GHz​​, verified through TDR (Time-Domain Reflectometry) testing.
• ​​Crosstalk Isolation​​: ​​>40 dB​​ between adjacent pairs, minimizing BER (Bit Error Rate) to ​​<1E-15​​.
• ​​Durability​​: Rated for ​​10,000 insertion cycles​​ with reinforced connectors and strain relief boots.

In lab tests, the cable sustained ​​400Gbps line rate​​ with ​​<0.5 ns/m latency​​ across 10,000 hours of continuous operation.

​​Key Use Cases and Deployment Scenarios​​

​​1. AI/ML Cluster Interconnects​​

A hyperscaler deployed 5,000 cables in ​​Nexus 93600CD-GX​​ switches to connect ​​NVIDIA DGX A100 systems​​, achieving ​​3.2 Tbps bisectional bandwidth​​ per rack. The passive design eliminated optical transceiver costs, saving ​​$2.1M per 10-rack cluster​​.

​​2. High-Frequency Trading (HFT) Backbones​​

A Tokyo stock exchange used the cables to link ​​Arista 7800R3​​ and Cisco Nexus 9336C-FX2 switches, achieving ​​98 ns end-to-end latency​​ for market data distribution—​​40% lower​​ than active optical solutions.

​​3. Cloud Storage Fabrics​​

A European MSP reduced SAN replication times by 70% using ​​400G SRv6-based storage over IP​​, leveraging the cable’s ​​lossless Ethernet​​ capabilities with ​​Cisco Nexus Dashboard​​ flow analytics.

​​Addressing Critical Deployment Concerns​​

​​Q: How does it compare to active optical cables (AOCs) for 400G?​​

While AOCs support longer distances (up to 100m), the NXA-QDD-2Q-CU1M= offers:

• ​​Cost Savings​​: ​​80% lower​​ upfront cost per port.
• ​​Power Efficiency​​: ​​0.1W vs. 1.5W​​ per port.
• ​​Latency​​: ​​0.5 ns/m vs. 3 ns/m​​ for AOCs.

​​Q: What’s the maximum operational temperature?​​

The cable operates at ​​0°C to 70°C​​ with ​​85% non-condensing humidity​​. For hotter environments, Cisco recommends ​​NXA-QDD-2Q-AOC3M=​​ active optical cables.

​​Q: Can it be used with non-Cisco switches?​​

Yes, but full ​​Forward Error Correction (FEC)​​ requires switches supporting ​​IEEE 802.3bj Clause 91​​. Compatibility with Arista 7060X2 and Juniper QFX5220 has been validated.

​​Installation and Maintenance Best Practices​​

1. ​​Bend Radius Management​​: Maintain ​​≥30 mm​​ bend radius to prevent signal degradation.
2. ​​Connector Care​​: Use ​​Cisco CMP-2Q-CLEANER​​ every 6 months to remove dust from QSFP-DD receptacles.
3. ​​Labeling​​: Apply ​​Cisco CAB-LBL-400G​​ flags to identify breakout configurations (e.g., 8x50G vs. 4x100G).
4. ​​Testing​​: Validate link integrity with ​​Cisco NX-OS CLI commands​​:

   show interface ethernet 1/1 transceiver details  
   show interface ethernet 1/1 counters errors  

For enterprises migrating from QSFP28 DACs, Cisco offers ​​trade-in credits covering 20% of costs​​ under its Cabling Modernization Program.

​​Why Enterprises Choose This Solution​​

• ​​Density​​: Enables ​​144x400G ports​​ in a 4RU Nexus 93600CD-GX chassis—​​3x​​ the density of QSFP-56 solutions.
• ​​Compliance​​: Meets ​​RoHS 3​​, ​​REACH SVHC​​, and ​​TAA​​ standards for global deployments.
• ​​Future-Proofing​​: Supports ​​800G upgrades​​ via firmware-enabled ​​PAM4-to-NRZ retimer​​ modes.

For pricing and bulk orders, visit the Cisco NXA-QDD-2Q-CU1M= product page at ITMall.sale.

​​Lessons from Hyperscale Deployments​​

Analyzing field data from 15+ hyperscalers reveals two operational truths:

1. ​​Cable Management Is Critical​​: A cloud provider reduced unplanned outages by 60% after implementing ​​Cisco’s Vertical Exhaust Rack (VER)​​ design, which eliminated cable stress in overhead trays.
2. ​​Heat Kills Predictably​​: A blockchain firm experienced ​​BER spikes​​ in cables routed near hot aisle containment barriers. Relocating cables ​​≥6 inches​​ from heat sources restored signal integrity.

While optical evangelists tout fiber’s supremacy, the NXA-QDD-2Q-CU1M= proves copper’s relevance in the 400G/800G era. For enterprises prioritizing cost, latency, and sustainability, this cable isn’t just a component—it’s the connective tissue of next-gen AI and cloud architectures. In an industry where every picosecond and watt counts, its value proposition remains unmatched.