Router, Not GPU Merger: How PAIR Actually Works
NVIDIA PAIR's core trick is almost sleight-of-hand: it proxies requests by taking over the default ports that Ollama and LM Studio already listen on [1], so any agent harness pointed at localhost keeps working without a single line of code changed. Behind that proxy sits a scheduler that checks three things before it routes a job - whether a paired node is online and ready, whether a supported inference engine is enabled on it, and whether the exact model being requested is already present there [1].
That scheduler is doing real work: mDNS discovery (a way devices find each other automatically on a local network, without manual IP configuration) locates compatible machines, and mTLS encryption (mutual TLS, where both sides of a connection present certificates to verify each other) secures the pairing before any inference traffic flows [2].
What PAIR pointedly does not do is merge GPUs, pool VRAM, or split a single inference request across multiple machines [1]- a scope NVIDIA flags explicitly in its own documentation. That distinction is the first thing technical users tend to probe: is this different from tools that combine several machines into one virtual accelerator? By NVIDIA's own description, yes - PAIR keeps each node's workload independent and hands whole jobs to whichever machine is free, rather than stitching machines into a single larger GPU the way model-sharding frameworks do.

