Spectrum-X

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Use Case

NVIDIA Spectrum-X multi-rail AI interconnect for Ethernet fabrics. Combines SR-IOV with multiplane load balancing to scale GPU-to-GPU bandwidth across switch tiers.

Two reference architectures are supported, selected by Network Operator release:

  • RA2.2 (current) — requires --network-operator-release 26.4. Uses SpectrumXRailPoolConfig (v1alpha2 CRD).

  • RA2.1 (previous) — requires --network-operator-release 26.1. Uses SriovNetworkPoolConfig + SriovNetworkNodePolicy + OVSNetwork with NV-IPAM glue.

For deeper Spectrum-X background, see Spectrum-X Configuration.

Multiplane Modes

The --multiplane-mode flag selects how planes are mapped onto NICs. --spectrum-x takes the SPC-X RA version as its value (RA2.1 or RA2.2); --multiplane-mode, --number-of-planes, and --network-operator-release are all required alongside it. --spectrum-x implies ethernet fabric, sriov deployment, and multirail.

HWPLB

Hardware Plane Load Balancing for larger-scale clusters with 2-tier or 3-tier switch topologies:

l8k generate --spectrum-x RA2.2 \
    --network-operator-release 26.4 \
    --multiplane-mode hwplb --number-of-planes 4

SWPLB

Software Plane Load Balancing for smaller-scale Spectrum-X clusters. Generates separate resources per-rail per-plane:

l8k generate --spectrum-x RA2.2 \
    --network-operator-release 26.4 \
    --multiplane-mode swplb --number-of-planes 2

Uniplane

Unified plane mode with no plane separation. Use with --number-of-planes 1:

l8k generate --spectrum-x RA2.2 \
    --network-operator-release 26.4 \
    --multiplane-mode uniplane --number-of-planes 1

None (Single Plane)

No multiplane separation. Use with BlueField-3 SuperNIC or simple topologies. none requires --number-of-planes 1:

l8k generate --spectrum-x RA2.2 \
    --network-operator-release 26.4 \
    --multiplane-mode none --number-of-planes 1

Side-by-side comparison of the four modes:

flowchart TB subgraph HWPLB[HWPLB - hardware load balancing] H_NIC[NIC] H_NIC -->|HW LB| H_P1[Plane 1] H_NIC -->|HW LB| H_P2[Plane 2] H_NIC -->|HW LB| H_P3[Plane 3] end subgraph SWPLB[SWPLB - software load balancing] S_NIC[NIC] --> S_OVS[OVS] S_OVS -->|SW LB| S_P1[Plane 1] S_OVS -->|SW LB| S_P2[Plane 2] S_OVS -->|SW LB| S_P3[Plane 3] end subgraph UNI[Uniplane] U_NIC[NIC] --> U_P[Single plane] end subgraph NONE[None] N_NIC[NIC] --> N_NET[Standard network] end

NIC Type Constraints

NIC Type

Device ID

Supported Modes

ConnectX-8

1023

swplb, hwplb, uniplane

BlueField-3 SuperNIC

a2dc

none only

Pinning to RA2.1

For Network Operator 26.1 deployments, select the Spectrum-X RA2.1 profile by passing RA2.1 as the value of --spectrum-x:

l8k generate --spectrum-x RA2.1 \
    --network-operator-release 26.1 \
    --multiplane-mode swplb --number-of-planes 2

If the release and Spectrum-X version are mismatched (for example, --spectrum-x RA2.1 with --network-operator-release 26.4), Launch Kit errors out with an explicit message.

See Also