OVS-TEST(8)                      Open vSwitch                      OVS-TEST(8)

       ovs-test  -  Check Linux drivers for performance, vlan and L3 tunneling

       ovs-test -s port

       ovs-test -c server1 server2 [-b targetbandwidth] [-i testinterval] [-d]
              [-l vlantag] [-t tunnelmodes]

       The ovs-test program may be used to check for problems  sending  802.1Q
       or GRE traffic that Open vSwitch may uncover. These problems, for exam‐
       ple, can occur when Open vSwitch is used to send 802.1Q traffic through
       physical  interfaces  running  certain  drivers of certain Linux kernel
       versions.  To run a test, configure IP addresses on server1 and server2
       for interfaces you intended to test. These interfaces could also be al‐
       ready configured OVS bridges that have a physical interface attached to
       them. Then, on one of the nodes, run ovs-test in server mode and on the
       other node run it in client mode. The client will connect  to  ovs-test
       server  and  schedule  tests  between both of them. The ovs-test client
       will perform UDP and TCP tests.

       UDP tests can report packet loss and  achieved  bandwidth  for  various
       datagram sizes. By default target bandwidth for UDP tests is 1Mbit/s.

       TCP  tests  report  only  achieved  bandwidth, because kernel TCP stack
       takes care of flow control and packet loss. TCP tests are essential  to
       detect potential TSO related issues.

       To  determine  whether  Open  vSwitch is encountering any problems, the
       user must compare packet loss and achieved bandwidth in a  setup  where
       traffic  is  being  directly sent and in one where it is not. If in the
       802.1Q or L3 tunneled tests both ovs-test processes are unable to  com‐
       municate  or  the  achieved  bandwidth is much lower compared to direct
       setup, then, most likely, Open vSwitch has encountered  a  pre-existing
       kernel or driver bug.

       Some examples of the types of problems that may be encountered are:

       • When NICs use VLAN stripping on receive they must pass a pointer to a
         vlan_group when reporting the stripped tag to the networking core. If
         no  vlan_group  is  in  use then some drivers just drop the extracted
         tag.  Drivers are supposed to only enable stripping if  a  vlan_group
         is registered but not all of them do that.

       • On receive, some drivers handle priority tagged packets specially and
         don’t pass the tag onto the network stack at  all,  so  Open  vSwitch
         never has a chance to see it.

       • Some drivers size their receive buffers based on whether a vlan_group
         is enabled, meaning that a maximum size packet with a VLAN  tag  will
         not fit if no vlan_group is configured.

       • On  transmit, some drivers expect that VLAN acceleration will be used
         if it is available, which can only be done if a vlan_group is config‐
         ured.  In  these  cases,  the driver may fail to parse the packet and
         correctly setup checksum offloading or TSO.

       Client Mode
              An ovs-test client will connect to two ovs-test servers and will
              ask  them to exchange test traffic. It is also possible to spawn
              an ovs-test server automatically from the client.

       Server Mode
              To conduct tests, two ovs-test servers must be  running  on  two
              different  hosts  where  the client can connect. The actual test
              traffic is exchanged only between both ovs-test servers.  It  is
              recommended  that  both  servers  have their IP addresses in the
              same subnet, otherwise one would have to make sure that  routing
              is set up correctly.

       -s <port>, --server <port>
              Run  in server mode and wait for the client to establish XML RPC
              Control Connection on this TCP port. It is recommended  to  have
              ethtool(8) installed on the server so that it could retrieve in‐
              formation about the NIC driver.

       -c <server1> <server2>, --client <server1> <server2>
              Run in client  mode  and  schedule  tests  between  server1  and
              server2,  where  each server must be given in the following for‐


              The OuterIP must be already assigned to the  physical  interface
              which is going to be tested. This is the IP address where client
              will  try  to  establish  XML  RPC  connection.  If  OuterIP  is
      then client will automatically spawn a local instance
              of ovs-test server.  OuterPort is TCP port where server is  lis‐
              tening  for  incoming  XML/RPC  control  connections to schedule
              tests (by default it is 15531). The ovs-test will  automatically
              assign  InnerIP[/Mask] to the interfaces that will be created on
              the  fly  for  testing  purposes.  It  is  important  that   In‐
              nerIP[/Mask]  does  not  interfere  with already existing IP ad‐
              dresses on both ovs-test servers and client. InnerPort  is  port
              which  will  be  used  by server to listen for test traffic that
              will be encapsulated (by default it is 15532).

       -b <targetbandwidth>, --bandwidth <targetbandwidth>
              Target bandwidth for UDP  tests.  The  targetbandwidth  must  be
              given  in  bits per second. It is possible to use postfix M or K
              to alter the target bandwidth magnitude.

       -i <testinterval>, --interval <testinterval>
              How long each test should run. By default 5 seconds.

       -h, --help
              Prints a brief help message to the console.

       -V, --version
              Prints version information to the console.

       The following test modes are supported by ovs-test. It is  possible  to
       combine multiple of them in a single ovs-test invocation.

       -d, --direct
              Perform direct tests between both OuterIP addresses. These tests
              could be used as a reference to compare 802.1Q or  L3  tunneling
              test results.

       -l <vlantag>, --vlan-tag <vlantag>
              Perform 802.1Q tests between both servers. These tests will cre‐
              ate a temporary OVS bridge, if  necessary,  and  attach  a  VLAN
              tagged port to it for testing purposes.

       -t <tunnelmodes>, --tunnel-modes <tunnelmodes>
              Perform  L3 tunneling tests. The given argument is a comma sepa‐
              rated string that specifies all the L3 tunnel modes that  should
              be  tested  (e.g.  gre). The L3 tunnels are terminated on inter‐
              face that has the OuterIP address assigned.

       On host start ovs-test in server mode:

          ovs-test -s 15531

       On host start ovs-test in client mode and do direct,  VLAN  and
       GRE tests between both nodes:

          ovs-test -c,, -d -l 123 -t

       ovs-vswitchd(8), ovs-ofctl(8), ovs-vsctl(8), ovs-vlan-test, ethtool(8),

       The Open vSwitch Development Community

       2016-2021, The Open vSwitch Development Community

3.3                              Feb 17, 2024                      OVS-TEST(8)