Preface: When server partners like Supermicro, Dell, Lenovo, and Gigabyte build 4U or 8U systems using the NVIDIA HGX H100 platform, the underlying architecture decouples internal GPU communication from external cluster communication.
Internal (Node-Level): The HGX baseboard houses the 4 or 8 H100 SXM GPUs and 4 NVSwitch chips. GPU-to-GPU traffic inside the single chassis flows exclusively over NVLink via the NVSwitches at 900 GB/s per GPU. No ConnectX or BlueField chips are involved in this intra-node traffic.
External (Scale-Out Cluster Networking): To connect multiple 4U/8U servers together into an AI cluster (scale-out) and hook them up to storage, the server chassis integrates NVIDIA ConnectX and NVIDIA BlueField network adapters via PCIe Gen 5 slots.
Background: NVIDIA combines Arm cores, ConnectX adapters, and data processing units (DPUs) into a single platform (like the NVIDIA BlueField DPU Platform) to offload infrastructure tasks, accelerate AI data movement, and enforce zero-trust security. This design frees up the main server CPU, boosts network throughput, and isolates management from user workloads.
The VIRTIO_F_MRG_RX_BUFFER feature is negotiated by the VirtIO controller running on the ARM cores, but its execution is fully offloaded to the NVIDIA NIC hardware ASIC.
The architecture splits these networking responsibilities:
1. NVIDIA ConnectX (The “East-West” Compute Fabric)
2. NVIDIA BlueField (The “North-South” Management & Storage Fabric)
This article focuses on the second part (2).
An 8-GPU server typically utilizes 1 or 2 BlueField-3 DPUs (or high-end dual-port ConnectX cards configured for storage).
BlueField DPUs feature onboard ARM processor cores and automated hardware accelerators. They isolate and manage the operating system’s connection to NVMe-over-Fabrics (NVMe-oF) storage, handle security firewalls, and route virtualization layers so the host x86 CPUs do not waste processing cycles on network overhead.
The virtio-net-controller lives entirely inside the NVIDIA BlueField DPU subsystem. It does not run on the host x86 CPU or the ConnectX cards. In HGX H100 4U/8U multi-GPU architectures, the virtio-net-controller is a specialized background service (systemd) running on the BlueField DPU’s internal ARM operating system. It serves a critical purpose: hardware-accelerated network virtualization for multi-tenant AI clouds.
Vulnerability details: CVE-2026-65094 – NVIDIA VIRTIO-Net for Bluefield contains a vulnerability in Virtio-Net where a VM user may cause a Write-What-Where condition by crafted message. A successful exploit of this vulnerability may lead to code execution in Virtio-Net scope.
Official announcement: Please refer to link for details – https://nvidia.custhelp.com/app/answers/detail/a_id/5815