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A GPU cluster has four separate networks. Name them and say what each one carries.

Most architecture diagrams show one network and a cluster has four. Each has a different traffic pattern, a different failure consequence and a different port count, and the one that is under-counted every time is the one you need when everything else is broken.

Updated Sep 2026 · Grounded in real AI infrastructure interview loops and written to a senior-engineer editorial bar, with every number worked and every diagram hand-built.

Most architecture diagrams show one network and a cluster has four. Each has a different traffic pattern, a different failure consequence and a different port count, and the one that is under-counted every time is the one you need when everything else is broken.

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The concepts behind this question

Ranked by how closely each one overlaps this question's topic, so the first card is the thing to read if the answer above moved too fast.

🖧 Hardware & Cluster Build-Out

The Bill of Materials for a Training ClusterA GPU cluster is not a pile of GPUs. A 512-GPU scalable unit built to NVIDIA's DGX SuperPOD B300 reference architecture needs 64 nodes, four separate networks, thousands of transceivers, storage that can absorb a checkpoint burst, a management plane, racks, power distribution and cooling equipment. Writing the list out in order is how a design becomes a purchase order, and the items people forget are the ones that hold up a deployment for weeks.

📐 AI Systems Design

Inference Platform ArchitectureAn LLM inference platform is the layer between a product's API call and a GPU running a serving engine, and every design round starts from its reference shape: a gateway that authenticates and rate-limits, a router that picks a replica with the right model and a warm cache, a per-replica scheduler that batches, engines that run prefill and decode, a KV cache tier, an autoscaler, and the observability that makes it operable. This page draws that shape, sizes each box for a concrete workload, and walks the derivation from user demand to replica count that every design answer has to contain.

📐 AI Systems Design

Multi-Region Serving and FailoverRunning inference in more than one region buys latency for distant users and survival when a region fails, and it costs a second fleet that must be capable of absorbing the first one's traffic. The design turns on three decisions: whether regions are active-active or active-passive, what state has to cross regions and what deliberately does not, and how much headroom each region carries so a failover does not simply move the outage.

📐 AI Systems Design

Control Plane and API Design for GPU PlatformsEvery GPU platform has a control plane, and its API is what the rest of the organization experiences as the platform. Three semantics decide whether it survives contact with a network: idempotent creation so a retried request does not launch a second job on sixty-four GPUs, cancellation modelled as intent because only the node agent can stop a running process, and cursor pagination that does not skip rows when work is created during a listing.

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UP NEXT ON YOUR JOURNEY

Next in this trackDesign the fabric for 10,000 GPUs. Two tiers or three, and what does the choice cost?Next in this trackFor 64 to 72 GPUs, is one GB300 NVL72 rack better than eight HGX B300 nodes?Next in this trackBuy hardware, colocate, or rent from a GPU cloud? Work the decision for a 512-GPU need.

FEDITOR'S NOTE

Scored on naming all four with their distinct traffic patterns, on why they are separate rather than VLANs, and on the port counts that follow.

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