1 Replacing a Linux Bridge with Open vSwitch
2 ==========================================
4 This file documents how Open vSwitch may be used as a drop-in
5 replacement for a Linux kernel bridge in an environment that includes
6 elements that are tightly tied to the Linux bridge tools
7 (e.g. "brctl") and architecture. We recommend directly using the
8 management tools provided with Open vSwitch rather than these
9 compatibility hooks for environments that are not tightly tied to the
10 Linux bridging tools; they are more efficient and better reflect the
11 actual operation and status.
14 Installation Procedure
15 ----------------------
17 The procedure below explains how to use the Open vSwitch bridge
18 compatibility support. This procedure is written from the perspective
19 of a system administrator manually loading and starting Open vSwitch
20 in bridge compatibility mode, but of course in practice one would want
21 to update system scripts to follow these steps.
23 1. Build and install the Open vSwitch kernel modules and userspace
24 programs as described in INSTALL.Linux.
26 It is important to run "make install", because some Open vSwitch
27 programs expect to find files in locations selected at installation
30 2. Load both the openvswitch and brcompat kernel modules (which were
31 built in step 1), e.g.:
33 % insmod datapath/linux-2.6/openvswitch_mod.ko
34 % insmod datapath/linux-2.6/brcompat_mod.ko
36 These kernel modules cannot be loaded if the Linux bridge module is
37 already loaded. Thus, you may need to remove any existing bridges
38 and unload the bridge module with "rmmod bridge" before you can do
39 this. In addition, if you edit your system configuration files to
40 load these modules at boot time, it should happen before any bridge
41 configuration (e.g. before any calls to "brctl" or "ifup" of any
42 bridge interfaces), to ensure that the Open vSwitch kernel modules
43 are loaded before the Linux kernel bridge module.
45 3. Create an initial version of the configuration file, for example
46 /etc/ovs-vswitchd.conf. This file may be empty initially or may
47 contain add any valid configuration directives described in
48 ovs-vswitchd.conf(5). However, it must exist when you start
51 To create an empty configuration file:
53 % touch /etc/ovs-vswitchd.conf
55 4. Start ovs-vswitchd and ovs-brcompatd, e.g.:
57 % ovs-vswitchd -P -D -vANY:console:EMER /etc/ovs-vswitchd.conf
58 % ovs-brcompatd -P -D -vANY:console:EMER /etc/ovs-vswitchd.conf
60 5. Now you should be able to manage the Open vSwitch using brctl and
61 related tools. For example, you can create an Open vSwitch bridge,
62 add interfaces to it, then print information about bridges with the
66 % brctl addif br0 eth0
67 % brctl addif br0 eth1
70 Each of these commands actually uses or modifies the Open vSwitch
71 configuration file, then notifies the ovs-vswitchd daemon of the
72 change. For example, after executing the commands above starting
73 from an empty configuration file, "cat /etc/ovs-vswitchd.conf"
74 should show that the configuration file now contains the following: