ovs-vlan-test - Check Linux drivers for problems with vlan traffic

       The Open vSwitch Development Community

       2016-2024, The Open vSwitch Development Community

3.5                                               Jun 30, 2025                                  OVS-VLAN-TEST(8)

       The  ovs-vlan-test  utility  has some limitations, for example, it does not use TCP in its tests. Also it
       does not take into account MTU to detect potential edge cases. To overcome those limitations a  new  tool
       was developed - ovs-test. ovs-test is currently supported only on Debian so, if possible, try to use that
       on instead of ovs-vlan-test.

       The  ovs-vlan-test  program may be used to check for problems sending 802.1Q traffic which may occur when
       running Open vSwitch. These problems 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
       Open vSwitch to tag traffic originating from vlan_ip and forward it out the target  interface.  Then  run
       the  ovs-vlan-test in client mode connecting to an ovs-vlan-test server.  ovs-vlan-test will display “OK”
       if it did not detect problems.

       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 configured. In these cases, the driver may fail  to  parse  the  packet  and
         correctly setup checksum offloading or TSO.

       ClientMode
              An  ovs-vlan-test  client may be run on a host to check for VLAN connectivity problems. The client
              must be able to establish HTTP connections with an ovs-vlan-test server located at  the  specified
              control_ip address. UDP traffic sourced at vlan_ip should be tagged and directed out the interface
              whose connectivity is being tested.

       ServerMode
              To  conduct  tests,  an  ovs-vlan-test  server  must  be  running on a host known not to have VLAN
              connectivity problems. The server must have a control_ip on a non-VLAN network which  clients  can
              establish  connectivity  with. It must also have a vlan_ip address on a VLAN network which clients
              will use to test their VLAN connectivity. Multiple clients may test against a single ovs-vlan-test
              server concurrently.

       Display the Linux kernel version and driver of eth1:

          uname -r
          ethtool -i eth1

       Set up a bridge which forwards traffic originating from 1.2.3.4 out eth1 with VLAN tag 10:

          ovs-vsctl -- add-br vlan-br \
            -- add-port vlan-br eth1 \
            -- add-port vlan-br vlan-br-tag tag=10 \
            -- set Interface vlan-br-tag type=internal
          ip addr add 1.2.3.4/8 dev vlan-br-tag
          ip link set vlan-br-tag up

       Run an ovs-vlan-test server listening for client control traffic  on  172.16.0.142  port  8080  and  VLAN
       traffic on the default port of 1.2.3.3:

          ovs-vlan-test -s 172.16.0.142:8080 1.2.3.3

       Run  an  ovs-vlan-test client with a control server located at 172.16.0.142 port 8080 and a local VLAN IP
       of 1.2.3.4:

          ovs-vlan-test 172.16.0.142:8080 1.2.3.4

       ovs-vlan-test - Check Linux drivers for problems with vlan traffic

-s,--server
              Run in server mode.

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

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

ovs-vswitchd(8), ovs-ofctl(8), ovs-vsctl(8), ovs-test, ethtool(8), uname(1)

ovs-vlan-test [-s | –server] control_ipvlan_ip