400G, 200G & 100G DAC Compatibility Guide for NVIDIA Platforms

1. Why Do AI Clusters Prefer DAC Cables?

In AI servers, GPU clusters, and High-Performance Computing (HPC) environments, the distance between servers and switches inside a rack is typically only 1–3 meters. Compared with optical transceivers, Direct Attach Copper (DAC) cables provide several significant advantages:

• Ultra-low latency

• Zero power consumption (Passive DAC)

• Lower deployment cost

• Simple cable management

• High reliability

These benefits make DAC cables the preferred short-reach interconnect solution for NVIDIA DGX systems, ConnectX network adapters, and Quantum InfiniBand and Spectrum Ethernet switches.

2. 400G, 200G & 100G DAC Product Portfolio

800G/400G/200G/100G/50G/40G/25G/10G DAC Cable丨C-LIGHT

3. NVIDIA (Mellanox) Platform Compatibility

(1) 100G DAC

100G DAC QSFP28/SFP28 1m-2m-3m-5m Cable丨C-LIGHT

Interface: QSFP28

Compatible platforms:

• ConnectX-4

• ConnectX-5

• ConnectX-6

• NVIDIA Spectrum Ethernet Switches

• Quantum EDR/HDR InfiniBand (selected models)

Typical applications include:

• 100GbE Ethernet

• EDR InfiniBand

• Enterprise storage networking

(2) 200G DAC

200G DAC QSFP56/QSFP-DD/QSFP28 Cable丨C-LIGHT

Interface: QSFP56

Compatible platforms:

• ConnectX-6

• ConnectX-7

• BlueField-2

• BlueField-3

• Quantum HDR InfiniBand

• Spectrum-2

• Spectrum-3

• Spectrum-4

The 200G QSFP56 DAC is the mainstream solution for HDR InfiniBand and 200GbE Ethernet deployments.

(3) 400G DAC

400G DAC QSFP112/OSFP56/QSFP-DD Cable丨C-LIGHT

Three interface options are commonly available.

QSFP-DD 400G DAC

Compatible with:

• Spectrum-3

• Spectrum-4

• ConnectX-6

• ConnectX-7

Designed primarily for 400GbE Ethernet networking.

QSFP112 400G DAC

Compatible with:

• ConnectX-7

• BlueField-3

QSFP112 ports support backward compatibility with QSFP56 (200G) and QSFP28 (100G) modules when operating in supported speed modes.

OSFP 400G DAC

Compatible with:

• Quantum-2 NDR InfiniBand

• Spectrum-4 Ethernet

• NVIDIA DGX H100

• NVIDIA DGX H200

OSFP is primarily designed for AI switches and high-density GPU systems.

(4) 800G DAC

800G DAC QSFP-DD/OSFP112 Cable丨C-LIGHT

OSFP112 800G DAC

Compatible with:

• Quantum-2 NDR InfiniBand

• Spectrum-4 Ethernet

• ConnectX-8

• ConnectX-9

The OSFP112 interface is designed for next-generation AI networking and ultra-high-density GPU deployments.

4. Recommended DAC Products for NVIDIA Platforms

5. DAC Breakout Applications

Common DAC breakout configurations in AI networking include:

For example, NVIDIA supports OSFP-to-4×100G QSFP56 breakout DAC cables, enabling high-density server connectivity within AI clusters.

6. C-LIGHT DAC Solutions

For AI data centers, HPC clusters, and enterprise networking, C-LIGHT offers a complete portfolio of high-speed DAC solutions, including:

Standard DAC Products

• 100G QSFP28 DAC

• 200G QSFP56 DAC

• 400G QSFP-DD DAC

• 400G QSFP112 DAC

• 400G OSFP DAC

• Passive DAC (P-DAC)

• Active Copper Cable (ACC/LACC)

Breakout DAC Solutions

• 400G to 200G DAC

• 400G to 100G DAC

• 200G to 100G DAC

• 100G to 25G DAC

Custom Services

• EEPROM compatibility programming

• NVIDIA (Mellanox) compatibility coding

• Customized cable lengths

• OEM/ODM manufacturing

Every C-LIGHT DAC cable undergoes interoperability testing with mainstream AI networking platforms to ensure stable and reliable deployment.

7. Deployment Recommendations

For optimal performance and compatibility, consider the following best practices:

1. Use Passive DAC for in-rack connections up to 3 meters.

2. For distances beyond 3 meters, choose ACC (Active Copper Cable) or AOC (Active Optical Cable).

3. Verify the physical interface before deployment, as OSFP, QSFP112, QSFP56, and QSFP28 are not mechanically compatible.

4. Select the appropriate cable based on the network protocol—InfiniBand or Ethernet.

5. Confirm firmware and EEPROM compatibility before installation to ensure seamless interoperability.

8. Conclusion

400G, 200G, and 100G DAC cables have become essential interconnect solutions for AI data centers, HPC environments, and cloud computing infrastructure. When selecting a DAC cable, users should consider the interface type, transmission speed, networking protocol (InfiniBand or Ethernet), and compatibility with NVIDIA ConnectX NICs, BlueField DPUs, Spectrum Ethernet switches, and Quantum InfiniBand platforms.

By choosing the appropriate DAC solution, organizations can achieve ultra-low latency, high reliability, excellent cost efficiency, and optimized GPU cluster performance.

9.Frequently Asked Questions (FAQ)