ovs-vlan-test(1)              Open vSwitch Manual             ovs-vlan-test(1)

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

       ovs-vlan-test [-s | --server] control_ip vlan_ip

       Common options:
              [-h | --help] [-V | --version]

       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  prob‐
       lems 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 origi‐
       nating 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 network‐
              ing 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

       ·      On  receive,  some  drivers  handle priority tagged packets spe‐
              cially 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.

   Client Mode
       An ovs-vlan-test client may be run on a host to check for VLAN  connec‐
       tivity 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.

   Server Mode
       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 connectiv‐
       ity  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.

              Run in server mode.

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

              Prints version information to the console.

       Display the Linux kernel version and driver of eth1.

              uname -r

              ethtool -i eth1

       Set  up  a  bridge  which forwards traffic originating from 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

              ifconfig vlan-br-tag up

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

              ovs-vlan-test -s

       Run   an   ovs-vlan-test  client  with  a  control  server  located  at port 8080 and a local VLAN ip of


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

Open vSwitch                        2.5.90                    ovs-vlan-test(1)