Open vSwitch, usually shortened to OVS, is a multilayer software switch built for virtualisation hosts. Its first release dates from July 2009 according to Wikipedia, and it has been a Linux Foundation project since August 2016, with the foundation also holding the trademark. The code is published under the Apache 2.0 license, and its kernel module has shipped inside mainline Linux since version 3.3 in 2012.
Version 4.0.0 was released on 17 August 2026 according to the project’s NEWS file, while the 3.7 branch remains the long-term support line, with 3.7.1 published at the end of March 2026.
What Open vSwitch is for
A hypervisor that hosts virtual machines has to give them a network: connect their virtual network cards to each other and to the outside world. Linux can do this with its built-in bridge, but the bridge was designed for simple jobs and offers neither movable state nor remote programmability. Open vSwitch replaces it with a real switch. It understands 802.1Q VLANs on trunk and access ports, link aggregation with or without LACP, quality of service and policing, port mirroring and NetFlow, sFlow and IPFIX export. It also builds Geneve, GRE, VXLAN, ERSPAN, GTP-U, SRv6 and Bareudp tunnels to stretch a virtual network across a physical one.
What sets it apart is that it is driven from outside. The ovs-vswitchd daemon reads its configuration from a small database served by ovsdb-server, which any program can modify remotely through the OVSDB protocol. Forwarding decisions are expressed as OpenFlow flow tables, written by hand with ovs-ofctl or managed by an SDN controller. When a virtual machine migrates to another host, its filtering rules, QoS settings and counters can follow it. The Linux kernel module handles fast packet processing, and a userspace datapath, accelerated by DPDK or AF_XDP, takes over where the kernel path is not enough.
This is also where it parts ways with Cilium, another project in this category. Cilium relies on eBPF to provide networking and security for Kubernetes pods, at the level of containers and service identities. Open vSwitch works one layer down, at the virtual port and the machine, and it is the building block found under OpenStack, Proxmox VE, oVirt, OpenNebula and XenServer, where it is the default switch. Its sibling project OVN, Open Virtual Network, layers logical L2 and L3 networks, virtual routers and security groups on top.
Who is it for?
Open vSwitch is for administrators of virtualisation platforms and private clouds, teams deploying OpenStack or OVN, SDN researchers and students who want to experiment with OpenFlow on ordinary hardware, and vendors using it as the control stack for their switching silicon. A small lab with a few KVM virtual machines is enough to get started.
The learning curve is steep, though. Bridges, ports, flow tables and the OVSDB database are all handled at the command line, with no graphical interface, and troubleshooting usually means ovs-appctl and reading flow dumps. Windows and Hyper-V support, offered for years, was deprecated in 3.7.0 and removed in 4.0.0 according to the NEWS file, so the 3.7 LTS branch is the last to carry it. For a Kubernetes cluster Cilium is the more direct route, and for a physical network a system such as VyOS or Cumulus Linux answers a different need.
Download Open vSwitch safely
The download page on openvswitch.org offers source tarballs for every release, including openvswitch-4.0.0.tar.gz and the 3.7.1 long-term support release, and links to the openvswitch/ovs repository on GitHub for development code. Building requires at least GCC 4.6 or Clang 3.4, Python 3.7 or newer and, for the kernel module, Linux 3.3 or later, with version 4.0 raising the floor to 4.3 for GRE, VXLAN and Geneve tunnels. Most administrators will simply install the openvswitch package from their distribution, Debian, Ubuntu, Fedora, RHEL or openSUSE, following the instructions in the official documentation at docs.openvswitch.org.
The software is free of charge, with no commercial edition or registration, and the project sells nothing. It no longer distributes a current Windows installer either, so an .msi file offered for a recent version cannot be genuine. More generally, an archive that comes neither from openvswitch.org, nor from the project’s GitHub repository, nor from your distribution’s repositories has no place on a hypervisor.
Frequently asked questions
Is Open vSwitch free?
Yes. It is released under the Apache 2.0 license by a project hosted at the Linux Foundation, with no paid edition. Companies that want support can buy it from third-party vendors, for instance as part of a commercial OpenStack distribution, but nothing requires it.
Does it run on Windows?
Not in recent versions. According to the project’s NEWS file, Windows and Hyper-V support was deprecated in 3.7.0 and removed in 4.0.0. The 3.7 LTS branch is the last to offer it, and it has to be compiled with Visual Studio.
How does it differ from the Linux bridge?
The Linux bridge is a simple, fast layer 2 switch. Open vSwitch adds a remotely queryable configuration database, OpenFlow flow tables, tunnels and network state that follows virtual machines as they migrate, which is what multi-server virtualisation platforms need.
