Q: What does it mean for an Open vSwitch release to be LTS (long-term support)?

A: All official releases have been through a comprehensive testing process and are suitable for production use. Planned releases occur twice a year. If a significant bug is identified in an LTS release, we will provide an updated release that includes the fix. Releases that are not LTS may not be fixed and may just be supplanted by the next major release. The current LTS release is 2.5.x.

For more information on the Open vSwitch release process, refer to Open vSwitch Release Process.

Q: What Linux kernel versions does each Open vSwitch release work with?

A: The following table lists the Linux kernel versions against which the given versions of the Open vSwitch kernel module will successfully build. The Linux kernel versions are upstream kernel versions, so Linux kernels modified from the upstream sources may not build in some cases even if they are based on a supported version. This is most notably true of Red Hat Enterprise Linux (RHEL) kernels, which are extensively modified from upstream.

Open vSwitch Linux kernel
1.4.x 2.6.18 to 3.2
1.5.x 2.6.18 to 3.2
1.6.x 2.6.18 to 3.2
1.7.x 2.6.18 to 3.3
1.8.x 2.6.18 to 3.4
1.9.x 2.6.18 to 3.8
1.10.x 2.6.18 to 3.8
1.11.x 2.6.18 to 3.8
2.0.x 2.6.32 to 3.10
2.1.x 2.6.32 to 3.11
2.3.x 2.6.32 to 3.14
2.4.x 2.6.32 to 4.0
2.5.x 2.6.32 to 4.3
2.6.x 3.10 to 4.7

Open vSwitch userspace should also work with the Linux kernel module built into Linux 3.3 and later.

Open vSwitch userspace is not sensitive to the Linux kernel version. It should build against almost any kernel, certainly against 2.6.32 and later.

Q: Are all features available with all datapaths?

A: Open vSwitch supports different datapaths on different platforms. Each datapath has a different feature set: the following tables try to summarize the status.

Supported datapaths:

Linux upstream
The datapath implemented by the kernel module shipped with Linux upstream. Since features have been gradually introduced into the kernel, the table mentions the first Linux release whose OVS module supports the feature.
Linux OVS tree
The datapath implemented by the Linux kernel module distributed with the OVS source tree.
Also known as DPDK, dpif-netdev or dummy datapath. It is the only datapath that works on NetBSD, FreeBSD and Mac OSX.
Also known as the Windows datapath.

The following table lists the datapath supported features from an Open vSwitch user’s perspective.

Feature Linux upstream Linux OVS tree Userspace Hyper-V
Connection tracking 4.3 YES PARTIAL PARTIAL
Tunnel - GRE 3.11 YES YES YES
Tunnel - VXLAN 3.12 YES YES YES
Tunnel - Geneve 3.18 YES YES YES
Tunnel - GRE-IPv6 NO NO YES NO
Tunnel - VXLAN-IPv6 4.3 YES YES NO
Tunnel - Geneve-IPv6 4.4 YES YES NO
QoS - Policing YES YES YES NO
QoS - Shaping YES YES NO NO

Do note, however:

  • Only a limited set of flow fields is modifiable via the set action by the Hyper-V datapath.
  • The Hyper-V datapath only supports one physical NIC per datapath. This is why bonding is not supported.
  • The Hyper-V datapath can have at most one IP address configured as a tunnel endpoint.

The following table lists features that do not directly impact an Open vSwitch user, e.g. because their absence can be hidden by the ofproto layer (usually this comes with a performance penalty).

Feature Linux upstream Linux OVS tree Userspace Hyper-V
SCTP flows 3.12 YES YES YES
Megaflows 3.12 YES YES NO
Masked set action 4.0 YES YES NO
Recirculation 3.19 YES YES YES
TCP flags matching 3.13 YES YES NO
Validate flow actions YES YES N/A NO
Multiple datapaths YES YES YES NO

Q: What DPDK version does each Open vSwitch release work with?

A: The following table lists the DPDK version against which the given versions of Open vSwitch will successfully build.

Open vSwitch DPDK
2.2.x 1.6
2.3.x 1.6
2.4.x 2.0
2.5.x 2.2
2.6.x 16.07

Q: I get an error like this when I configure Open vSwitch:

configure: error: Linux kernel in <dir> is version <x>, but
version newer than <y> is not supported (please refer to the
FAQ for advice)

What should I do?

A: You have the following options:

  • Use the Linux kernel module supplied with the kernel that you are using. (See also the following FAQ.)
  • If there is a newer released version of Open vSwitch, consider building that one, because it may support the kernel that you are building against. (To find out, consult the table in the previous FAQ.)
  • The Open vSwitch “master” branch may support the kernel that you are using, so consider building the kernel module from “master”.

All versions of Open vSwitch userspace are compatible with all versions of the Open vSwitch kernel module, so you do not have to use the kernel module from one source along with the userspace programs from the same source.

Q: What features are not available in the Open vSwitch kernel datapath that ships as part of the upstream Linux kernel?

A: The kernel module in upstream Linux does not include support for LISP. Work is in progress to add support for LISP to the upstream Linux version of the Open vSwitch kernel module. For now, if you need this feature, use the kernel module from the Open vSwitch distribution instead of the upstream Linux kernel module.

Certain features require kernel support to function or to have reasonable performance. If the ovs-vswitchd log file indicates that a feature is not supported, consider upgrading to a newer upstream Linux release or using the kernel module paired with the userspace distribution.

Q: Why do tunnels not work when using a kernel module other than the one packaged with Open vSwitch?

A: Support for tunnels was added to the upstream Linux kernel module after the rest of Open vSwitch. As a result, some kernels may contain support for Open vSwitch but not tunnels. The minimum kernel version that supports each tunnel protocol is:

Protocol Linux Kernel
GRE 3.11
VXLAN 3.12
Geneve 3.18
LISP not upstream
STT not upstream

If you are using a version of the kernel that is older than the one listed above, it is still possible to use that tunnel protocol. However, you must compile and install the kernel module included with the Open vSwitch distribution rather than the one on your machine. If problems persist after doing this, check to make sure that the module that is loaded is the one you expect.

Q: Why are UDP tunnel checksums not computed for VXLAN or Geneve?

A: Generating outer UDP checksums requires kernel support that was not part of the initial implementation of these protocols. If using the upstream Linux Open vSwitch module, you must use kernel 4.0 or newer. The out-of-tree modules from Open vSwitch release 2.4 and later support UDP checksums.

Q: What features are not available when using the userspace datapath?

A: Tunnel virtual ports are not supported, as described in the previous answer. It is also not possible to use queue-related actions. On Linux kernels before 2.6.39, maximum-sized VLAN packets may not be transmitted.

Q: Should userspace or kernel be upgraded first to minimize downtime?

A. In general, the Open vSwitch userspace should be used with the kernel version included in the same release or with the version from upstream Linux. However, when upgrading between two releases of Open vSwitch it is best to migrate userspace first to reduce the possibility of incompatibilities.

Q: What happened to the bridge compatibility feature?

A: Bridge compatibility was a feature of Open vSwitch 1.9 and earlier. When it was enabled, Open vSwitch imitated the interface of the Linux kernel “bridge” module. This allowed users to drop Open vSwitch into environments designed to use the Linux kernel bridge module without adapting the environment to use Open vSwitch.

Open vSwitch 1.10 and later do not support bridge compatibility. The feature was dropped because version 1.10 adopted a new internal architecture that made bridge compatibility difficult to maintain. Now that many environments use OVS directly, it would be rarely useful in any case.

To use bridge compatibility, install OVS 1.9 or earlier, including the accompanying kernel modules (both the main and bridge compatibility modules), following the instructions that come with the release. Be sure to start the ovs-brcompatd daemon.