If you have been researching how to connect two NVIDIA DGX Spark systems, you have probably seen several cable part numbers referenced: the Amphenol NJAAKK-N911, the Luxshare LMTQF022-SD-R, and the Mellanox MCP1650-V00AE30. This article explains what the NJAAKK-N911 is, how the DGX Spark's networking actually works, and how these cables relate to one another.
What Is the NJAAKK-N911?
The NJAAKK-N911 is a passive direct-attach copper (DAC) cable made by Amphenol, terminated in QSFP112 connectors on both ends and rated for up to 400G on hardware that supports it. NVIDIA lists it as one of two approved cables for connecting DGX Spark systems, alongside the Luxshare LMTQF022-SD-R. It is a 0.5 m cable, which is the practical length for two compact desktop units sitting side by side.
How the DGX Spark Connects: One Type of Port
This is the part that is easy to get wrong. The DGX Spark does not have a separate, proprietary "stacking port." According to NVIDIA's DGX Spark documentation, each Spark has two QSFP ports on the back, driven by the onboard ConnectX-7 NIC. Those same two ports are used both for connecting two Spark units directly and for general Ethernet / RoCE networking.
NVIDIA also specifies that each QSFP port provides up to 200 Gb/s, and that the port is capped at that rate. In NVIDIA's own words, using a higher-speed cable is not beneficial because the port itself is the limit. So while the NJAAKK-N911 is a QSFP112 / 400G-rated cable, on a DGX Spark the link runs at 200 Gb/s.
The Two NVIDIA-Approved Cables
For connecting DGX Spark systems, NVIDIA names two cables:
- NJAAKK-N911 (Amphenol) — QSFP112 passive DAC
- LMTQF022-SD-R (Luxshare) — the functionally equivalent QSFP112 passive DAC
Either of these is a safe, spec-matching choice. They are the same physical cable type from two different manufacturers.
Where the MCP1650-V00AE30 Fits
The MCP1650-V00AE30 is a 200G QSFP56 passive DAC. It is not one of the two parts NVIDIA names for the Spark, but because the Spark's ports run at 200 Gb/s, it is a viable, tried-and-tested lower-cost option for stacking two units. Our customers have used it successfully for exactly this purpose with no reported issues, and it is a good pick if you are looking to save money on the interconnect.
Good to Know
- Connect two units directly with a single cable — no switch, transceivers, or adapters required.
- The QSFP / ConnectX-7 ports operate in Ethernet mode (with RoCE), not InfiniBand.
- NVIDIA's clustering guidance covers connecting two or three Sparks directly, and up to four through a switch.
- The same ConnectX-7 networking is used on the OEM GB10 systems (HP ZGX Nano AI Station, Dell Pro Max with GB10, ASUS Ascent GX10), so the same approved cables apply.
Quick Summary
The NJAAKK-N911 is one of NVIDIA's two approved DGX Spark cables (with the Luxshare LMTQF022-SD-R). It is a QSFP112 / 400G-rated cable that runs at the Spark's 200 Gb/s port speed. There is no separate stacking port — the ConnectX-7 QSFP ports handle both stacking and networking. The MCP1650-V00AE30 is a viable lower-cost 200G alternative that works well in practice.
Related Guide
How to Connect Two NVIDIA DGX Spark Systems: The Cable You Need and Why
Shop This Product
NJAAKK-N911 QSFP112 400G-Rated Passive DAC Cable, 0.5m is available from Resilient Tec. For a lower-cost 200G option, see the MCP1650-V00AE30 200G QSFP56 DAC.