ovs-sim(1)                   Open vSwitch Manual                  ovs-sim(1)

NAME         top

       ovs-sim - Open vSwitch simulator environment

SYNOPSIS         top

       ovs-sim [option]... [script]...

DESCRIPTION         top

       ovs-sim provides a convenient environment for running one or more
       Open vSwitch instances and related software in a sandboxed simulation

       To use ovs-sim, first build Open vSwitch, then invoke it directly
       from the build directory, e.g.:

       git clone
       cd ovs

       When invoked in the most ordinary way as shown above, ovs-sim does
       the following:

                Creates a directory sandbox as a subdirectory of the current
                directory (first destroying such a directory if it already
                exists) and cds into that directory.

                Installs all of the Open vSwitch manpages into a man
                subdirectory of sandbox and adjusts the MANPATH environment
                variable so that man and other manpage viewers can find

                Creates a simulated Open vSwitch named main and sets it up
                as the default target for OVS commands, as if the following
                ovs-sim commands had been run:

                          sim_add main
                          as main

                See Commands, below, for an explanation.

                Runs any scripts specified on the command line (see Options
                below). The scripts can use arbitrary Bash syntax, plus the
                additional commands described under Commands, below.

                If no scripts were specified, or if -i or --interactive was
                specified, invokes an interactive Bash subshell. The user
                can use arbitrary Bash commands, plus the additional
                commands described under Commands, below.

       ovs-sim and the sandbox environment that it creates does not require
       superuser or other special privileges. Generally, it should not be
       run with such privileges.

OPTIONS         top

       ovs-sim accepts the following options and arguments:

              script Runs script, which should be a Bash script, within a
                     subshell after initializing. If multiple script
                     arguments are given, then they are run in the order
                     given. If any script exits with a nonzero exit code,
                     then ovs-sim exits immediately with the same exit code.

                   By default, if any script is specified, ovs-sim exits as
                   soon as the scripts finish executing. With this option,
                   or if no scripts are specified, ovs-sim instead starts an
                   interactive Bash session.

COMMANDS         top

       Scripts and interactive usage may use the following commands
       implemented by ovs-sim. They are implemented as Bash shell functions
       exported to subshells.

   Basic Commands
       These are the basic commands for working with sandboxed Open vSwitch

              sim_add sandbox
                     Starts a new simulated Open vSwitch instance named
                     sandbox. Files related to the instance, such as logs,
                     databases, sockets, and pidfiles, are created in a
                     subdirectory also named sandbox. Afterward, the as
                     command (see below) can be used to run Open vSwitch
                     utilities in the context of the new sandbox.

                     The new sandbox starts out without any bridges. Use
                     ovs-vsctl in the context of the new sandbox to create a
                     bridge, e.g.:

                     sim_add hv0           # Create sandbox hv0.
                     as hv0                # Set hv0 as default sandbox.
                     ovs-vsctl add-br br0  # Add bridge br0 inside hv0.

                     The Open vSwitch instances that sim_add create enable
                     ``dummy’’ devices. This means that bridges and
                     interfaces can be created with type dummy to indicate
                     that they should be totally simulated, without any
                     reference to system entities. In fact, ovs-sim also
                     configures Open vSwitch so that the default system type
                     of bridges and interfaces are replaced by dummy
                     devices. Other types of devices, however, retain their
                     usual functions, which means that, e.g., vxlan tunnels
                     still act as tunnels (refer to the documentation).

              as sandbox
                     Sets sandbox as the default simulation target for Open
                     vSwitch commands (e.g. ovs-vsctl, ovs-ofctl,

                     This command updates the beginning of the shell prompt
                     to indicate the new default target.

              as sandbox command arg...
                     Runs the given command with sandbox as the simulation
                     target, e.g. as hv0 ovs-vsctl add-br br0 runs ovs-vsctl
                     add-br br0 within sandbox hv0. The default target is

   Interconnection Network Commands
       When multiple sandboxed Open vSwitch instances exist, one will
       inevitably want to connect them together. These commands allow for
       that. Conceptually, an interconnection network is a switch that
       ovs-sim makes it easy to plug into other switches in other sandboxed
       Open vSwitch instances. Interconnection networks are implemented as
       bridges in the main switch that ovs-sim creates by default, so to use
       interconnection networks please avoid working with main directly.

              net_add network
                     Creates a new interconnection network named network.

              net_attach network bridge
                     Adds a new port to bridge in the default sandbox (as
                     set with as) and plugs it into the network
                     interconnection network. network must already have been
                     created by a previous invocation of net_add. The
                     default sandbox must not be main.

   OVN Commands
       These commands interact with OVN, the Open Virtual Network.

                     Creates and initializes the central OVN databases (both
                     ovn-sb(5) and ovn-nb) and starts an instance of
                     ovsdb-server for each one. Also starts an instance of

              ovn_attach network bridge ip [masklen]
                     First, this command attaches bridge to interconnection
                     network network, just like net_attach network bridge.
                     Second, it configures (simulated) IP address ip (with
                     network mask length masklen, which defaults to 24) on
                     bridge. Finally, it configures the Open vSwitch
                     database to work with OVN and starts ovn-controller.

EXAMPLES         top

       The following creates a pair of Open vSwitch instances hv0 and hv1,
       adds a port named vif0 or vif1, respectively, to each one, and then
       connects the two through an interconnection network n1:

       net_add n1
       for i in 0 1; do
           sim_add hv$i
           as hv$i ovs-vsctl add-br br0 -- add-port br0 vif$i
           as hv$i net_attach n1 br0

       Here’s an extended version that also starts OVN:

       ovn-nbctl ls-add lsw0
       net_add n1
       for i in 0 1; do
           sim_add hv$i
           as hv$i
           ovs-vsctl add-br br-phys
           ovn_attach n1 br-phys 192.168.0.`expr $i + 1`
           ovs-vsctl add-port br-int vif$i -- set Interface vif$i external-ids:iface-id=lp$i
           ovn-nbctl lsp-add lsw0 lp$i
           ovn-nbctl lsp-set-addresses lp$i f0:00:00:00:00:0$i

       Here’s a primitive OVN ``scale test’’ (adjust the scale by changing n
       in the first line :

       n=200; export n
       net_add n1
       ovn-nbctl ls-add br0
       for i in `seq $n`; do
           (sim_add hv$i
           as hv$i
           ovs-vsctl add-br br-phys
           y=$(expr $i / 256)
           x=$(expr $i % 256)
           ovn_attach n1 br-phys 192.168.$y.$x
           ovs-vsctl add-port br-int vif$i -- set Interface vif$i external-ids:iface-id=lp$i) &
           case $i in
               *50|*00) echo $i; wait ;;
       for i in `seq $n`; do
           yy=$(printf %02x $(expr $i / 256))
           xx=$(printf $02x $(expr $i % 256))
           ovn-nbctl lsp-add br0 lp$i
           ovn-nbctl lsp-set-addresses lp$i f0:00:00:00:$yy:$xx

       When the scale test has finished initializing, you can watch the
       logical ports come up with a command like this:

       watch ’for i in `seq $n`; do if test `ovn-nbctl lsp-get-up lp$i` != up; then echo $i; fi; done’

COLOPHON         top

       This page is part of the Open vSwitch (a distributed virtual
       multilayer switch) project.  Information about the project can be
       found at ⟨⟩.  If you have a bug report for
       this manual page, send it to  This page was
       obtained from the project's upstream Git repository
       ⟨⟩ on 2017-11-25.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2017-11-23.)  If you discover any rendering problems in
       this HTML version of the page, or you believe there is a better or
       more up-to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not part
       of the original manual page), send a mail to

Open vSwitch 2.8.90                ovs-sim                        ovs-sim(1)