1 Using Open vSwitch as a Simple OpenFlow Switch
2 ==============================================
4 Open vSwitch uses OpenFlow as its preferred method of remote flow table
5 configuration. This is the simplest method of using it with an OpenFlow
6 controller. All that is required is to follow the instructions in
7 INSTALL.Linux and add the bridge.<name>.controller set of parameters to the
8 ovs-vswitchd(8) configuration file as described in ovs-vswitchd.conf(5).
9 We recommend using OpenFlow in this manner. However, it is also possible to
10 use Open vSwitch as a simple OpenFlow switch like that provided by the
11 OpenFlow reference implementation [1]. The remainder of this file describes
12 how to user it in that manner.
17 OpenFlow is a flow-based switch specification designed to enable
18 researchers to run experiments in live networks. OpenFlow is based on a
19 simple Ethernet flow switch that exposes a standardized interface for
20 adding and removing flow entries.
22 An OpenFlow switch consists of three parts: (1) A "flow table" in
23 which each flow entry is associated with an action telling the switch
24 how to process the flow, (2) a "secure channel" that connects the switch
25 to a remote process (a controller), allowing commands and packets to
26 be sent between the controller and the switch, and (3) an OpenFlow
27 protocol implementation, providing an open and standard way for a
28 controller to talk to the switch.
30 An OpenFlow switch can thus serve as a simple datapath element that
31 forwards packets between ports according to flow actions defined by
32 the controller using OpenFlow commands. Example actions are:
34 - Forward this flow's packets to the given port(s)
35 - Drop this flow's packets
36 - Encapsulate and forward this flow's packets to the controller.
38 The OpenFlow switch is defined in detail in the OpenFlow switch
41 Installation Procedure
42 ----------------------
44 The procedure below explains how to use the Open vSwitch as a simple
47 1. Build and install the Open vSwitch kernel modules and userspace
48 programs as described in INSTALL.Linux.
50 It is important to run "make install", because some Open vSwitch
51 programs expect to find files in locations selected at installation
54 2. Load the openvswitch kernel module (which was built in step 1), e.g.:
56 % insmod datapath/linux-2.6/openvswitch_mod.ko
58 This kernel module cannot be loaded if the Linux bridge module is
59 already loaded. Thus, you may need to remove any existing bridges
60 and unload the bridge module with "rmmod bridge" before you can do
63 3. Create a datapath instance. The command below creates a datapath
64 identified as dp0 (see ovs-dpctl(8) for more detailed usage
67 # ovs-dpctl add-dp dp0
69 Creating datapath dp0 creates a new network device, also named dp0.
70 This network device, called the datapath's "local port", will be
71 bridged to the physical switch ports by ovs-openflowd(8). It is
72 optionally used for in-band control as described in step 5.
74 4. Use ovs-dpctl to attach the datapath to physical interfaces on the
75 machine. Say, for example, you want to create a trivial 2-port
76 switch using interfaces eth1 and eth2, you would issue the following
79 # ovs-dpctl add-if dp0 eth1
80 # ovs-dpctl add-if dp0 eth2
82 You can verify that the interfaces were successfully added by asking
83 ovs-dpctl to print the current status of datapath dp0:
87 5. Arrange so that the switch can reach the controller over the network.
88 This can be done in two ways. The switch may be configured for
89 out-of-band control, which means it uses a network separate from the
90 data traffic that it controls. Alternatively, the switch may be
91 configured to contact the controller over one of the network devices
92 under its control. In-band control is often more convenient than
93 out-of-band, because it is not necessary to maintain two independent
96 - If you are using out-of-band control, at this point make sure
97 that the switch machine can reach the controller over the
100 - If you are using in-band control, then at this point you must
101 configure the dp0 network device created in step 3. This
102 device is not yet bridged to any physical network (because
103 ovs-openflowd does that, and it is not yet running), so the next
104 step depends on whether connectivity is required to configure
105 the device's IP address:
107 * If the switch has a static IP address, you may configure
108 its IP address now, e.g.:
110 # ifconfig dp0 192.168.1.1
112 * If the switch does not have a static IP address, e.g. its
113 IP address is obtained dynamically via DHCP, then proceed
114 to the next step. The DHCP client will not be able to
115 contact the DHCP server until the secure channel has
116 started. The address will be obtained in step 7.
118 - If you are using in-band control with controller discovery, no
119 configuration is required at this point. You may proceed to
122 6. Run ovs-openflowd to start the secure channel connecting the datapath to
123 a remote controller. If the controller is running on host
124 192.168.1.2 port 6633 (the default port), the ovs-openflowd invocation
125 would look like this:
127 # ovs-openflowd dp0 tcp:192.168.1.2
129 - If you are using in-band control with controller discovery, omit
130 the second argument to the ovs-openflowd command.
132 - If you are using out-of-band control, add --out-of-band to the
135 Using the "tcp:<controller_ip>" argument causes the switch to connect
136 in an insecure manner. Please see INSTALL.SSL for a description of
137 how to connect securely using SSL.
139 7. If you are using in-band control with manual configuration, and the
140 switch obtains its IP address dynamically, then you may now obtain
141 the switch's IP address, e.g. by invoking a DHCP client. The
142 secure channel will only be able to connect to the controller after
143 an IP address has been obtained.
145 8. The secure channel should connect to the controller within a few
146 seconds. It may take a little longer if controller discovery is in
147 use, because the switch must then also obtain its own IP address
148 and the controller's location via DHCP.
153 [1] OpenFlow Reference Implementation.
154 <http://www.openflowswitch.org/wp/downloads/>
156 [2] OpenFlow Switch Specification.
157 <http://openflowswitch.org/documents/openflow-spec-latest.pdf>