1 Using Open vSwitch as a Simple OpenFlow Switch
2 ==============================================
4 Open vSwitch uses OpenFlow as its preferred method of remote flow
5 table configuration. This is the simplest method of using it with an
6 OpenFlow controller. The ovs-vsctl "set-controller" command will set
7 the controller for one or more bridges. We recommend using OpenFlow
10 However, it is also possible to use Open vSwitch as a simple OpenFlow
11 switch like that provided by the OpenFlow reference implementation
12 [1]. The remainder of this file describes how to use it in that
18 OpenFlow is a flow-based switch specification designed to enable
19 researchers to run experiments in live networks. OpenFlow is based on a
20 simple Ethernet flow switch that exposes a standardized interface for
21 adding and removing flow entries.
23 An OpenFlow switch consists of three parts: (1) A "flow table" in
24 which each flow entry is associated with an action telling the switch
25 how to process the flow, (2) a "secure channel" that connects the switch
26 to a remote process (a controller), allowing commands and packets to
27 be sent between the controller and the switch, and (3) an OpenFlow
28 protocol implementation, providing an open and standard way for a
29 controller to talk to the switch.
31 An OpenFlow switch can thus serve as a simple datapath element that
32 forwards packets between ports according to flow actions defined by
33 the controller using OpenFlow commands. Example actions are:
35 - Forward this flow's packets to the given port(s)
36 - Drop this flow's packets
37 - Encapsulate and forward this flow's packets to the controller.
39 The OpenFlow switch is defined in detail in the OpenFlow switch
42 Installation Procedure
43 ----------------------
45 The procedure below explains how to use the Open vSwitch as a simple
48 1. Build and install the Open vSwitch kernel modules and userspace
49 programs as described in INSTALL.Linux.
51 It is important to run "make install", because some Open vSwitch
52 programs expect to find files in locations selected at installation
55 2. Load the openvswitch kernel module (which was built in step 1), e.g.:
57 % insmod datapath/linux-2.6/openvswitch_mod.ko
59 This kernel module cannot be loaded if the Linux bridge module is
60 already loaded. Thus, you may need to remove any existing bridges
61 and unload the bridge module with "rmmod bridge" before you can do
64 3. Create a datapath instance. The command below creates a datapath
65 identified as dp0 (see ovs-dpctl(8) for more detailed usage
68 # ovs-dpctl add-dp dp0
70 Creating datapath dp0 creates a new network device, also named dp0.
71 This network device, called the datapath's "local port", will be
72 bridged to the physical switch ports by ovs-openflowd(8). It is
73 optionally used for in-band control as described in step 5.
75 4. Use ovs-dpctl to attach the datapath to physical interfaces on the
76 machine. Say, for example, you want to create a trivial 2-port
77 switch using interfaces eth1 and eth2, you would issue the following
80 # ovs-dpctl add-if dp0 eth1
81 # ovs-dpctl add-if dp0 eth2
83 You can verify that the interfaces were successfully added by asking
84 ovs-dpctl to print the current status of datapath dp0:
88 5. Arrange so that the switch can reach the controller over the network.
89 This can be done in two ways. The switch may be configured for
90 out-of-band control, which means it uses a network separate from the
91 data traffic that it controls. Alternatively, the switch may be
92 configured to contact the controller over one of the network devices
93 under its control. In-band control is often more convenient than
94 out-of-band, because it is not necessary to maintain two independent
97 - If you are using out-of-band control, at this point make sure
98 that the switch machine can reach the controller over the
101 - If you are using in-band control, then at this point you must
102 configure the dp0 network device created in step 3. This
103 device is not yet bridged to any physical network (because
104 ovs-openflowd does that, and it is not yet running), so the next
105 step depends on whether connectivity is required to configure
106 the device's IP address:
108 * If the switch has a static IP address, you may configure
109 its IP address now, e.g.:
111 # ifconfig dp0 192.168.1.1
113 * If the switch does not have a static IP address, e.g. its
114 IP address is obtained dynamically via DHCP, then proceed
115 to the next step. The DHCP client will not be able to
116 contact the DHCP server until the secure channel has
117 started. The address will be obtained in step 7.
119 - If you are using in-band control with controller discovery, no
120 configuration is required at this point. You may proceed to
123 6. Run ovs-openflowd to start the secure channel connecting the datapath to
124 a remote controller. If the controller is running on host
125 192.168.1.2 port 6633 (the default port), the ovs-openflowd invocation
126 would look like this:
128 # ovs-openflowd dp0 tcp:192.168.1.2
130 - If you are using in-band control with controller discovery, omit
131 the second argument to the ovs-openflowd command.
133 - If you are using out-of-band control, add --out-of-band to the
136 Using the "tcp:<controller_ip>" argument causes the switch to connect
137 in an insecure manner. Please see INSTALL.SSL for a description of
138 how to connect securely using SSL.
140 7. If you are using in-band control with manual configuration, and the
141 switch obtains its IP address dynamically, then you may now obtain
142 the switch's IP address, e.g. by invoking a DHCP client. The
143 secure channel will only be able to connect to the controller after
144 an IP address has been obtained.
146 8. The secure channel should connect to the controller within a few
147 seconds. It may take a little longer if controller discovery is in
148 use, because the switch must then also obtain its own IP address
149 and the controller's location via DHCP.
154 [1] OpenFlow Reference Implementation.
155 <http://www.openflowswitch.org/wp/downloads/>
157 [2] OpenFlow Switch Specification.
158 <http://openflowswitch.org/documents/openflow-spec-latest.pdf>