Frequently Asked Questions
==========================
+General
+-------
+
+Q: What is Open vSwitch?
+
+A: Open vSwitch is a production quality open source software switch
+ designed to be used as a vswitch in virtualized server environments. A
+ vswitch forwards traffic between different VMs on the same physical host
+ and also forwards traffic between VMs and the physical network. Open
+ vSwitch supports standard management interfaces (e.g. sFlow, NetFlow,
+ RSPAN, CLI), and is open to programmatic extension and control using
+ OpenFlow and the OVSDB management protocol.
+
+ Open vSwitch as designed to be compatible with modern switching
+ chipsets. This means that it can be ported to existing high-fanout
+ switches allowing the same flexible control of the physical
+ infrastructure as the virtual infrastructure. It also means that
+ Open vSwitch will be able to take advantage of on-NIC switching
+ chipsets as their functionality matures.
+
+Q: What virtualization platforms can use Open vSwitch?
+
+A: Open vSwitch can currently run on any Linux-based virtualization
+ platform (kernel 2.6.18 and newer), including: KVM, VirtualBox, Xen,
+ Xen Cloud Platform, XenServer. As of Linux 3.3 it is part of the
+ mainline kernel. The bulk of the code is written in platform-
+ independent C and is easily ported to other environments. We welcome
+ inquires about integrating Open vSwitch with other virtualization
+ platforms.
+
+Q: How can I try Open vSwitch?
+
+A: The Open vSwitch source code can be built on a Linux system. You can
+ build and experiment with Open vSwitch on any Linux machine.
+ Packages for various Linux distributions are available on many
+ platforms, including: Debian, Ubuntu, Fedora.
+
+ You may also download and run a virtualization platform that already
+ has Open vSwitch integrated. For example, download a recent ISO for
+ XenServer or Xen Cloud Platform. Be aware that the version
+ integrated with a particular platform may not be the most recent Open
+ vSwitch release.
+
+Q: Does Open vSwitch only work on Linux?
+
+A: No, Open vSwitch has been ported to a number of different operating
+ systems and hardware platforms. Most of the development work occurs
+ on Linux, but the code should be portable to any POSIX system. We've
+ seen Open vSwitch ported to a number of different platforms,
+ including FreeBSD, Windows, and even non-POSIX embedded systems.
+
+ By definition, the Open vSwitch Linux kernel module only works on
+ Linux and will provide the highest performance. However, a userspace
+ datapath is available that should be very portable.
+
+Q: What's involved with porting Open vSwitch to a new platform or
+ switching ASIC?
+
+A: The PORTING document describes how one would go about porting Open
+ vSwitch to a new operating system or hardware platform.
+
+Q: Why would I use Open vSwitch instead of the Linux bridge?
+
+A: Open vSwitch is specially designed to make it easier to manage VM
+ network configuration and monitor state spread across many physical
+ hosts in dynamic virtualized environments. Please see WHY-OVS for a
+ more detailed description of how Open vSwitch relates to the Linux
+ Bridge.
+
+Q: How is Open vSwitch related to distributed virtual switches like the
+ VMware vNetwork distributed switch or the Cisco Nexus 1000V?
+
+A: Distributed vswitch applications (e.g., VMware vNetwork distributed
+ switch, Cisco Nexus 1000V) provide a centralized way to configure and
+ monitor the network state of VMs that are spread across many physical
+ hosts. Open vSwitch is not a distributed vswitch itself, rather it
+ runs on each physical host and supports remote management in a way
+ that makes it easier for developers of virtualization/cloud
+ management platforms to offer distributed vswitch capabilities.
+
+ To aid in distribution, Open vSwitch provides two open protocols that
+ are specially designed for remote management in virtualized network
+ environments: OpenFlow, which exposes flow-based forwarding state,
+ and the OVSDB management protocol, which exposes switch port state.
+ In addition to the switch implementation itself, Open vSwitch
+ includes tools (ovs-controller, ovs-ofctl, ovs-vsctl) that developers
+ can script and extend to provide distributed vswitch capabilities
+ that are closely integrated with their virtualization management
+ platform.
+
+Q: Why doesn't Open vSwitch support distribution?
+
+A: Open vSwitch is intended to be a useful component for building
+ flexible network infrastructure. There are many different approaches
+ to distribution which balance trade-offs between simplicity,
+ scalability, hardware compatibility, convergence times, logical
+ forwarding model, etc. The goal of Open vSwitch is to be able to
+ support all as a primitive building block rather than choose a
+ particular point in the distributed design space.
+
+Q: How can I contribute to the Open vSwitch Community?
+
+A: You can start by joining the mailing lists and helping to answer
+ questions. You can also suggest improvements to documentation. If
+ you have a feature or bug you would like to work on, send a mail to
+ one of the mailing lists:
+
+ http://openvswitch.org/mlists/
+
+
+
+Releases
+--------
+
+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 will
+ occur several times 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
+ 1.4.x.
+
+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 3.3 and later does not include
+ the following features:
+
+ - Bridge compatibility, that is, support for the ovs-brcompatd
+ daemon that (if you enable it) lets "brctl" and other Linux
+ bridge tools transparently work with Open vSwitch instead.
+
+ We do not expect bridge compatibility to ever be available in
+ upstream Linux. If you need bridge compatibility, use the
+ kernel module from the Open vSwitch distribution instead of the
+ upstream Linux kernel module.
+
+ - Tunnel virtual ports, that is, interfaces with type "gre",
+ "ipsec_gre", "capwap". It is possible to create tunnels in
+ Linux and attach them to Open vSwitch as system devices.
+ However, they cannot be dynamically created through the OVSDB
+ protocol or set the tunnel ids as a flow action.
+
+ Work is in progress in adding these features to the upstream
+ Linux version of the Open vSwitch kernel module. For now, if
+ you need these features, use the kernel module from the Open
+ vSwitch distribution instead of the upstream Linux kernel
+ module.
+
+ - Patch virtual ports, that is, interfaces with type "patch".
+ You can use Linux "veth" devices as a substitute.
+
+ We don't have any plans to add patch ports upstream.
+
+Q: What features are not available when using the userspace datapath?
+
+A: Tunnel and patch 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.
+
+
Configuration Problems
----------------------
point, so the same problems will show up with the Linux bridge or
any other way to do bridging.
+Q: Is there any documentation on the database tables and fields?
+
+A: Yes. ovs-vswitchd.conf.db(5) is a comprehensive reference.
+
VLANs
-----
that works around bugs in kernel drivers. To enable VLAN
splinters on interface eth0, use the command:
- ovs-vsctl set interface eth0 other-config:enable-vlan-splinters=true
+ ovs-vsctl set interface eth0 other-config:enable-vlan-splinters=true
For VLAN splinters to be effective, Open vSwitch must know
which VLANs are in use. See the "VLAN splinters" section in
Controllers
-----------
+Q: What versions of OpenFlow does Open vSwitch support?
+
+A: Open vSwitch supports OpenFlow 1.0. It also includes a number of
+ extensions that bring many of the features from later versions of
+ OpenFlow. Work is underway to provide support for later versions and
+ can be tracked here:
+
+ http://openvswitch.org/development/openflow-1-x-plan/
+
Q: I'm getting "error type 45250 code 0". What's that?
A: This is a Open vSwitch extension to OpenFlow error codes. Open
A: See answer under "VLANs", above.
+Q: I ran "ovs-ofctl add-flow br0 nw_dst=192.168.0.1,actions=drop"
+ but I got a funny message like this:
+
+ ofp_util|INFO|normalization changed ofp_match, details:
+ ofp_util|INFO| pre: nw_dst=192.168.0.1
+ ofp_util|INFO|post:
+
+ and when I ran "ovs-ofctl dump-flows br0" I saw that my nw_dst
+ match had disappeared, so that the flow ends up matching every
+ packet.
+
+A: The term "normalization" in the log message means that a flow
+ cannot match on an L3 field without saying what L3 protocol is in
+ use. The "ovs-ofctl" command above didn't specify an L3 protocol,
+ so the L3 field match was dropped.
+
+ In this case, the L3 protocol could be IP or ARP. A correct
+ command for each possibility is, respectively:
+
+ ovs-ofctl add-flow br0 ip,nw_dst=192.168.0.1,actions=drop
+
+ and
+
+ ovs-ofctl add-flow br0 arp,nw_dst=192.168.0.1,actions=drop
+
+ Similarly, a flow cannot match on an L4 field without saying what
+ L4 protocol is in use. For example, the flow match "tp_src=1234"
+ is, by itself, meaningless and will be ignored. Instead, to match
+ TCP source port 1234, write "tcp,tp_src=1234", or to match UDP
+ source port 1234, write "udp,tp_src=1234".
+
+Q: How can I figure out the OpenFlow port number for a given port?
+
+A: The OFPT_FEATURES_REQUEST message requests an OpenFlow switch to
+ respond with an OFPT_FEATURES_REPLY that, among other information,
+ includes a mapping between OpenFlow port names and numbers. From a
+ command prompt, "ovs-ofctl show br0" makes such a request and
+ prints the response for switch br0.
+
+ The Interface table in the Open vSwitch database also maps OpenFlow
+ port names to numbers. To print the OpenFlow port number
+ associated with interface eth0, run:
+
+ ovs-vsctl get Interface eth0 ofport
+
+ You can print the entire mapping with:
+
+ ovs-vsctl -- --columns=name,ofport list Interface
+
+ but the output mixes together interfaces from all bridges in the
+ database, so it may be confusing if more than one bridge exists.
+
+ In the Open vSwitch database, ofport value -1 means that the
+ interface could not be created due to an error. (The Open vSwitch
+ log should indicate the reason.) ofport value [] (the empty set)
+ means that the interface hasn't been created yet. The latter is
+ normally an intermittent condition (unless ovs-vswitchd is not
+ running).
+
Contact
-------
projects / openvswitch / blobdiff