DGX Spark Interconnect Reference: NJAAKK-N911 and LMTQF022-SD-R

What the approved DGX Spark stacking cables are, what they actually deliver, and what to buy at two, three and four or more nodes.

Maintained by Resilient Tec · last verified 14 August 2026 · see also our NVIDIA DGX Spark Interconnect Compatibility Matrix

Short answer

NVIDIA approves exactly two cables for connecting DGX Spark systems directly. They are functionally the same cable from two manufacturers, and either one works:

  • Amphenol NJAAKK-N911 — QSFP to QSFP112, 32AWG, 400 mm, LSZH. The 0.5 m variant is NJAAKK0006.
  • Luxshare LMTQF022-SD-R — QSFP112 400G DAC, 400 mm, 30AWG.

If you have seen both numbers and wondered which you need: you do not need both, and neither is a substitute-of-lesser-quality for the other. They are the two approved sources for one specification.

Identification

Amphenol part number NJAAKK-N911 (400 mm) · NJAAKK0006 (0.5 m)
Luxshare part number LMTQF022-SD-R (400 mm)
Also sold as PNY DGX Spark Stacking Cable · "NVIDIA DGX Spark Connect Cable" · "Spark stacking / cluster cable"
Connector QSFP112, both ends
Cable type Passive direct attach copper (DAC). No transceivers, no power, no firmware.
Rated 400G (4 × 100G lanes)
Delivered on DGX Spark Up to 200 Gb/s per port — see throughput
Conductor gauge 32AWG (Amphenol) · 30AWG (Luxshare)
Jacket LSZH (Amphenol)
Host port ConnectX-7, QSFP, on GB10-based systems
Port mode Ethernet only. The QSFP ports do not run native InfiniBand.

Compatibility

Any GB10-based system exposing the ConnectX-7 QSFP ports takes the same cable. The DGX Spark design is licensed to several OEMs, and the interconnect does not change between them.

System Ports Cable
NVIDIA DGX Spark 2 × QSFP (ConnectX-7) Yes
ASUS Ascent GX10 2 × QSFP (ConnectX-7) Yes
Dell Pro Max with GB10 2 × QSFP (ConnectX-7) Yes
HP ZGX Nano AI Station 2 × QSFP (ConnectX-7) Yes
Standard QSFP-DD switch port QSFP-DD No — QSFP-DD cages are physically deeper; you need an adapter or breakout cable

Throughput: what you actually get

The cable is rated 400G. A DGX Spark port tops out at 200 Gb/s. NVIDIA's own guidance is simply to use cables known to deliver at least 200 Gb/s — a faster cable buys you nothing here.

The more useful detail, which is not obvious from any spec sheet: GB10 connects to the ConnectX-7 over two PCIe Gen5 x4 links rather than one wider link, because the GB10 silicon cannot present a wider-than-x4 interface per device. Each x4 link is roughly 100 Gbps, and the NIC runs in multi-host mode to aggregate them. The operating system sees four network interfaces behind two physical ports.

Plan for it as 2 × 100G, not 2 × 200G. Independent testing with RoCE and parallel streams measured 185–190 Gbps in practice. Bind your interfaces carelessly and the same hardware delivers 80–100 Gbps — not a cable fault, and no cable will fix it.

What to buy, by cluster size

Spark 1 Spark 2 1 × DAC, port 0 to port 0 2 nodes — no switch

Two nodes. One cable, port 0 on each unit. This is the case the approved cable list exists for. Buy one NJAAKK-N911 or LMTQF022-SD-R and you are done.

Spark 1 Spark 2 Spark 3 3 nodes — ring, 3 cables, both ports per unit, still no switch

Three nodes. Three cables in a ring, using both QSFP ports on every unit. Still no switch. This is the configuration most people do not realise is supported, and it is the last one that is.

400G managed switch Spark 1 Spark 2 Spark 3 Spark 4 4+ nodes — QSFP-DD to 2 × QSFP56 breakout, switch ports pinned to 200G

Four or more nodes. A managed switch becomes mandatory, and this cable stops being the answer. Switch ports are QSFP-DD, which is physically deeper than the QSFP112 cage on the Spark, so you need either QSFP-DD to QSFP56 adapter cables or QSFP-DD to dual-QSFP56 breakout cables. Breakouts are the better buy: two of them fill four switch ports and serve up to eight nodes.

The mistake that costs 75% of your bandwidth

After cabling a switch, set each connected port to 200 Gbps manually. Left on auto-negotiate, these links commonly settle at 50 Gbps. The cluster works, nothing errors, and you quietly lose three quarters of your fabric. Check it before you benchmark anything.

Selection summary

Nodes Switch What you need
2 No 1 × NJAAKK-N911 or LMTQF022-SD-R
3 No 3 × NJAAKK-N911 or LMTQF022-SD-R, ring topology
4–8 Yes 400G managed switch + 2 × QSFP-DD to 2 × QSFP56 breakout DAC, ports pinned to 200G
Citing this page. If you sell or support GB10 systems and want to reference this compatibility data on your own product pages, you are welcome to — a link back to this page is all we ask. If you find something here that is wrong or out of date, tell us and we will correct it.

Sources