Introduction
The 100G Passive Direct Attach Cable (DAC) is a key component for building efficient and cost-effective network interconnections.
To help you achieve stable and reliable 100G connectivity between different brands and models of equipment, we’ve prepared this concise selection guide.
It walks you through four core factors — protocol, transmission distance, cable connection type, and device compatibility — and concludes with our product recommendations to help you accurately identify the cable you need.
Step 1: Select the Protocol Type
Different devices support different network communication protocols. Please confirm before purchasing.
- Ethernet / RoCE: Suitable for standard Ethernet environments or RDMA over Converged Ethernet (RoCE) applications, commonly used in most network equipment.
- InfiniBand: Designed for High-Performance Computing (HPC) or low-latency networks, typically used in specialized cluster systems.
Step 2: Determine Transmission Distance
Available lengths:
- 1m
- 1.5m
- 2m
- 2.5m
- 3m
- 5m
(Other lengths under 5m can be customized. Selection tip: measure the actual distance between device ports and choose a cable slightly longer for flexibility.
For in-rack connections, 1–3m is recommended; for inter-rack connections, 5m is suitable.
If the required length exceeds 5m, we recommend using an Active Optical Cable (AOC) or optical modules with patch cords instead.)
Step 3: Choose the Cable Type — Direct or Breakout
- Straight (Direct Attach): One port directly connects to another port, ideal for point-to-point connections.
- Breakout: One high-speed port splits into multiple lower-speed ports, suitable for connecting multiple devices or bandwidth breakout applications.
- 100G → 2×50G
- 100G → 4×25G
Step 4: Confirm Compatibility of Device A
4.1 Identify the device type for one end of the DAC:
- Router
- Switch
- Server
- Storage
- Network Card (NIC / HCA)
4.2 Confirm the device brand:
- Huawei (HW)
- NVIDIA / Mellanox
- Cisco
- Juniper
- Dell, Intel, Broadcom, etc.
4.3 Provide the device model
4.4 Select the connector form factor:
- QSFP28
- SFP56-DD
- DSFP56, etc.
4.5 Select data rate:
- 100GbE
Step 5: Confirm Compatibility of Device B
5.1 Identify the device type for the other end of the DAC:
- Router
- Switch
- Server
- Storage
- Network Card (NIC / HCA)
5.2 Confirm the device brand:
- Huawei (HW)
- NVIDIA / Mellanox
- Cisco
- Juniper
- Dell, Intel, Broadcom, etc.
5.3 Provide the device model
5.4 Select the connector form factor:
- QSFP28
- SFP56-DD
- DSFP56
- SFP28
- SFP56, etc.
5.5 Select data rate:
- 100GbE
- 50GbE
- 25GbE
Once the above information is provided, our professional sales team will promptly recommend the correct DAC cable and ensure fast delivery.
What 100G Passive DAC Cables Does Vchung Offer?
(Product details to be inserted here.)
Pro Tip — Troubleshooting
If a compatible DAC does not function properly, check whether there’s another DAC cable nearby that works normally.
Perform a quick swap test to determine whether the issue lies with the DAC.
This is the standard diagnostic procedure also used by network equipment manufacturers.
- If replacing the DAC restores the link, the issue likely comes from the cable assembly — please contact our support team.
- If the link still fails to establish, the DAC can be ruled out, and further investigation into other potential causes is needed.
End
Vchung specializes in optical interconnect solutions for data centers and enterprise networks, offering a full range of products including:
1.25G / 10G / 25G / 40G / 100G / 200G / 400G / 800G optical transceivers,
high-speed InfiniBand optical modules,
Active Optical Cables (AOC),
high-speed Direct Attach Cables (DAC),
high-density MPO pre-terminated patch cords,
high-density fiber patch panels,
module boxes, and adapter panels —
covering the entire suite of structured cabling products for modern data centers.