​​Product Overview and Core Functionality​​

The ​​Cisco QSFP-4SFP10G-CU1M=​​ is a ​​high-density passive copper breakout cable​​ designed to interconnect 40G QSFP+ ports with four 10G SFP+ interfaces. This 1-meter Direct Attach Cable (DAC) enables cost-effective migration from 10G to 40G infrastructures without replacing existing switches, ideal for ​​top-of-rack (ToR) aggregation​​ and ​​storage area network (SAN)​​ expansions. Its ​​4x10G breakout capability​​ simplifies cabling while maintaining backward compatibility with legacy 10G devices.

​​Technical Specifications and Signal Integrity​​

​​Electrical and Mechanical Properties​​

• ​​Connector Configuration​​: ​​QSFP+ (40G) to 4×SFP+ (10G)​​, 1-meter passive twinaxial copper.
• ​​Data Rate​​: Supports ​​10GBASE-CR​​ and ​​40GBASE-CR4​​ per ​​IEEE 802.3bj​​, with ​​auto-negotiation​​ disablement recommended for stable links.
• ​​Cable Construction​​: ​​30 AWG​​ conductors with foil+braid shielding, ensuring ≤0.5 dB insertion loss at 10 GHz.

​​Environmental Tolerance​​

• ​​Operating Temperature​​: ​​0°C to 70°C​​, derating not required for data center deployments.
• ​​Bend Radius​​: ​​25 mm minimum​​ to prevent impedance mismatches.
• ​​EMI Resilience​​: Tested for ​​EN 55032 Class B​​ emissions compliance in dense racks.

​​Target Use Cases and Economic Benefits​​

​​Data Center Server Aggregation​​

Connects ​​Cisco Nexus 5672UP​​ (40G uplinks) to legacy ​​UCS C220 M4 servers​​ (10G NICs), delaying costly switch upgrades by 3–5 years.

​​Hyperconverged Infrastructure (HCI)​​

• ​​vSAN Traffic Segmentation​​: Isolate ​​VMware vSAN​​ traffic on dedicated 10G lanes while maintaining 40G spine connectivity.
• ​​Cost Savings​​: Reduces per-port costs by ​​60%​​ compared to four discrete 10G DAC cables.

​​High-Frequency Trading (HFT)​​

Achieves ​​sub-500 ns latency​​ for market data feeds between ​​Cisco Nexus 3172PQ​​ switches and FPGA-based trading engines.

​​Compatibility and Platform Support​​

​​Validated Cisco Devices​​

• ​​Switches​​: Nexus 5600/6000/9000 Series, Catalyst 3850/9300 with ​​network-advantage licenses​​.
• ​​Routers​​: ASR 1000 Series with ​​ESP-100/ESP-200​​ line cards in 40G mode.

​​Third-Party Interoperability​​

• ​​Brocade ICX 7750​​: Verified for ​​MLAG configurations​​ without packet storms.
• ​​NetApp FAS8200​​: Supports ​​SAN MTU jumbo frames (9216 bytes)​​ via ​​10G iSCSI​​.

​​Installation Best Practices​​

​​Physical Deployment Guidelines​​

1. ​​Cable Routing​​: Avoid parallel runs with power cables; maintain ≥50 mm separation.
2. ​​Strain Relief​​: Secure breakout legs with hook-and-loop straps near connectors.
3. ​​Port Mapping​​: Label SFP+ ends (e.g., “QSFP1/1-4”) to simplify troubleshooting.

​​Software Configuration​​

• ​​Interface Modes​​: Set QSFP+ port to ​​“breakout” mode​​ via Cisco NX-OS:

  interface Ethernet1/1  
    channel-group 1 mode active  

• ​​Flow Control​​: Enable ​​priority flow control (PFC)​​ on storage-facing 10G ports.

​​Troubleshooting Common Performance Issues​​

​​CRC Errors on 10G Links​​

• ​​Root Cause​​: Ground loops in mixed AC/DC power environments.
• ​​Solution​​: Install ​​isolating transformers​​ or use ​​SFP+ optical modules​​ for electrical isolation.

​​QSFP+ Port Not Recognizing Breakout​​

• ​​Diagnosis​​: Verify switch SKU supports breakout (e.g., Nexus 56128P requires ​​N56-B960-K9​​ license).
• ​​Resolution​​: Upgrade NX-OS to ​​7.1(0)N1(1)​​ or later.

​​Procurement and Vendor Considerations​​

For guaranteed compatibility and warranty coverage, “QSFP-4SFP10G-CU1M=” is available through ITMall.sale, offering ​​Cisco’s Limited Lifetime Warranty​​ and bulk order discounts (≥50 units).

​​Engineer’s Perspective: Strategic vs. Tactical Deployments​​

While the QSFP-4SFP10G-CU1M= excels in tactical cost-saving scenarios, its passive design imposes distance limitations (≤3m) and lacks diagnostic features like ​​Digital Optical Monitoring (DOM)​​. For enterprises planning 25G/100G migrations within 18 months, investing in ​​active optical cables (AOCs)​​ or ​​fiber breakout​​ might yield better ROI. However, in environments where 10G endpoints dominate (e.g., legacy medical imaging systems), this cable remains indispensable for bridging generational tech divides without forklift upgrades. The key is aligning its use with clear sunset timelines for 10G assets—otherwise, temporary fixes risk becoming permanent technical debt.