OpenBMC and FBOSS on Network Switch

Author: Dean Kala, Arista Networks; Mike Choy, Meta Collection: 2025-OCP-Global-Summit-Networking

Summary

Arista Networks and Meta have been co-developing network switches since 2017, beginning with the 128x100G Tomahawk 3 switch which first added a BMC to what was traditionally a BMC-less Arista design. This talk documents the evolution from "BMC Classic" architecture — where the BMC directly manages all platform sensors, fans, and power components via SMBus — to "BMC Light" (BMC-Lite), where those responsibilities shift to the main x86 CPU running Meta's FBOSS network operating system, while the BMC retains its critical role as a watchdog and out-of-band recovery mechanism.

The primary drivers for adopting BMC-Lite were speed of NPI (new product introduction) and the need to simultaneously deliver a network operating system across multiple new platforms as Meta's AI cluster infrastructure scaled. BMC-Lite achieves this by making platform management config-driven (JSON configuration files replace boilerplate code), moving complex platform services into user-space daemons on the x86 CPU, and standardizing a "Board Support Package" that Arista delivers with kernel drivers and configuration, enabling Meta's FBOSS software to work on day one. The FBOSS OSS Test Suite — which runs against this BSP — further reduces joint debugging effort.