Cumulus Linux is an operating system for network switches, built on the Debian distribution, which NVIDIA ships on its Spectrum Ethernet switches. It was born at Cumulus Networks, a Mountain View company that championed the idea of managing a switch like an ordinary Linux server, and which NVIDIA acquired in May 2020, at a time when the system already ran on more than a hundred hardware platforms according to the buyer’s announcement. Unlike most entries in our software library, this is a proprietary product governed by an NVIDIA licence agreement and sold together with the hardware. The documentation describes version 5.18 as based on Debian bookworm.
What Cumulus Linux is for
The founding idea is straightforward: since switching chips are bought off the shelf, nothing forces anyone to drive them with a closed system. Cumulus Linux installs a full Debian on the switch, and a service called switchd programs the ASIC so that the decisions taken by the Linux kernel, routes, ARP tables and VLANs, are applied at hardware speed. The administrator therefore gets apt, systemd and the familiar network interfaces, can install their own tools, and still enjoys a data plane capable of hundreds of gigabits.
Routing is handled by FRRouting, the free suite we present elsewhere in this library. It brings BGP, OSPF and EVPN, and NVIDIA adds contributions of its own such as unnumbered interfaces or the Prescriptive Topology Manager. Since version 5.0 the official command interface is called NVUE: it describes the whole configuration as an object model reachable from the command line and through a REST API, which makes it easy to generate configurations automatically with Ansible or during zero-touch provisioning.
The difference from VyOS, FRRouting and Arista EOS, its neighbours in the same category, comes down to hardware support. VyOS is a software router installed on a server or a virtual machine that processes packets in the CPU. FRRouting is only a routing daemon with no data plane. Arista EOS is also a proprietary system tied to its maker’s switches. Cumulus Linux stands between the two worlds: the freedom of a generic Linux, but only on NVIDIA Spectrum switches, which today range from the SN2000 series to the 800 Gbit/s SN6600 mentioned in the 5.18 release notes.
Typical deployments are leaf-spine fabrics in data centres, EVPN-VXLAN networks that stretch layer 2 segments over a routed underlay, and more recently Ethernet fabrics for compute and AI clusters. The 5.18 release notes mention high-frequency telemetry or adaptive routing, features that only make sense on a physical switch.
Who is it for?
Cumulus Linux is aimed at data centre and hosting network teams that run NVIDIA Spectrum switches and want to manage them with the same automation tools as their servers. It also interests students and engineers designing EVPN architectures, provided they go through simulation. NVIDIA Air, the virtual environment hosted by the vendor, lets anyone build a small virtual data centre with two racks and a leaf-spine fabric free of charge, according to the documentation.
The limits are mostly commercial and hardware-related. The software is not sold on its own: every switch must be bought with Cumulus Linux and a support contract of one, three or five years, and the perpetual licence covers one switch at a time. It does not run on a server or on an arbitrary box, and the Cumulus VX virtual machine image, long offered for download, is no longer published, as the documentation states. For a free software router VyOS is the natural path; for a plain routing daemon FRRouting is enough.
Download Cumulus Linux safely
There is no public download page. The official image, a self-extracting .bin file named for instance cumulus-linux-5.18.0-mlx-amd64.bin, is fetched from the NVIDIA Enterprise Support portal at enterprise-support.nvidia.com after signing in with an account attached to an active contract. It is then installed through ONIE, the boot environment of open switches, from an HTTP server, a USB stick or directly from an earlier release with the onie-install command. The installation guide warns that the operation wipes the existing configuration.
To simply try the system, the official route is NVIDIA Air, reached from the trial button on the product page, which leads to an NVIDIA sign-in page. Any Cumulus Linux image offered on a forum, a file-sharing site or an unofficial repository is at best outdated and at worst tampered with, and installing it would in any case breach the licence agreement, which forbids redistribution of the software.
Frequently asked questions
Is Cumulus Linux free?
No. It is proprietary software whose perpetual licence is sold per switch, together with NVIDIA Spectrum hardware and a mandatory support contract. Since version 4.4 no licence key has to be entered on the switch any more, but a purchase is still required for every device.
Can I test Cumulus Linux without buying a switch?
Yes, through NVIDIA Air, the simulation platform hosted by NVIDIA, which the documentation describes as a free personal virtual network available after creating an account. The former Cumulus VX image for the KVM hypervisor is no longer distributed.
Is Cumulus Linux an ordinary Linux?
Largely. Version 5.18 is based on Debian bookworm, with apt, systemd and the usual commands. The components that program the switching chip and the NVUE interface are proprietary, however, and the licence agreement forbids reverse engineering them.
