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

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

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

       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 de‐
       tect 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 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-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 speci‐
              fied 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 connectivity with. It must also have a vlan_ip address
              on a VLAN network which clients will use to test their VLAN con‐
              nectivity.   Multiple   clients   may   test  against  a  single
              ovs-vlan-test server concurrently.

       -s, --server
              Run in server mode.

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

       -V, --version
              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
          ip addr add dev vlan-br-tag
          ip link set 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, ethtool(8), un‐

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3.3                              Feb 17, 2024                 OVS-VLAN-TEST(8)