1OVS-VLAN-TEST(8) Open vSwitch OVS-VLAN-TEST(8)
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6 ovs-vlan-test - Check Linux drivers for problems with vlan traffic
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9 ovs-vlan-test [-s | –server] control_ip vlan_ip
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12 The ovs-vlan-test utility has some limitations, for example, it does
13 not use TCP in its tests. Also it does not take into account MTU to de‐
14 tect potential edge cases. To overcome those limitations a new tool was
15 developed - ovs-test. ovs-test is currently supported only on Debian
16 so, if possible, try to use that on instead of ovs-vlan-test.
17 The ovs-vlan-test program may be used to check for problems sending
19 802.1Q traffic which may occur when running Open vSwitch. These prob‐
20 lems can occur when Open vSwitch is used to send 802.1Q traffic through
21 physical interfaces running certain drivers of certain Linux kernel
22 versions. To run a test, configure Open vSwitch to tag traffic origi‐
23 nating from vlan_ip and forward it out the target interface. Then run
24 the ovs-vlan-test in client mode connecting to an ovs-vlan-test server.
25 ovs-vlan-test will display “OK” if it did not detect problems.
26 Some examples of the types of problems that may be encountered are:
28 • When NICs use VLAN stripping on receive they must pass a pointer to a
30 vlan_group when reporting the stripped tag to the networking core. If
31 no vlan_group is in use then some drivers just drop the extracted
32 tag. Drivers are supposed to only enable stripping if a vlan_group
33 is registered but not all of them do that.
34 • On receive, some drivers handle priority tagged packets specially and
36 don’t pass the tag onto the network stack at all, so Open vSwitch
37 never has a chance to see it.
38 • Some drivers size their receive buffers based on whether a vlan_group
40 is enabled, meaning that a maximum size packet with a VLAN tag will
41 not fit if no vlan_group is configured.
42 • On transmit, some drivers expect that VLAN acceleration will be used
44 if it is available, which can only be done if a vlan_group is config‐
45 ured. In these cases, the driver may fail to parse the packet and
46 correctly setup checksum offloading or TSO.
47 Client Mode
49 An ovs-vlan-test client may be run on a host to check for VLAN
50 connectivity problems. The client must be able to establish HTTP
51 connections with an ovs-vlan-test server located at the speci‐
52 fied control_ip address. UDP traffic sourced at vlan_ip should
53 be tagged and directed out the interface whose connectivity is
54 being tested.
55 Server Mode
57 To conduct tests, an ovs-vlan-test server must be running on a
58 host known not to have VLAN connectivity problems. The server
59 must have a control_ip on a non-VLAN network which clients can
60 establish connectivity with. It must also have a vlan_ip address
61 on a VLAN network which clients will use to test their VLAN con‐
62 nectivity. Multiple clients may test against a single
63 ovs-vlan-test server concurrently.
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66 -s, --server
67 Run in server mode.
68 -h, --help
70 Prints a brief help message to the console.
71 -V, --version
73 Prints version information to the console.
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76 Display the Linux kernel version and driver of eth1:
77 uname -r
79 ethtool -i eth1
80 Set up a bridge which forwards traffic originating from 1.2.3.4 out
82 eth1 with VLAN tag 10:
83 ovs-vsctl -- add-br vlan-br \
85 -- add-port vlan-br eth1 \
86 -- add-port vlan-br vlan-br-tag tag=10 \
87 -- set Interface vlan-br-tag type=internal
88 ip addr add 1.2.3.4/8 dev vlan-br-tag
89 ip link set vlan-br-tag up
90 Run an ovs-vlan-test server listening for client control traffic on
92 172.16.0.142 port 8080 and VLAN traffic on the default port of 1.2.3.3:
93 ovs-vlan-test -s 172.16.0.142:8080 1.2.3.3
95 Run an ovs-vlan-test client with a control server located at
97 172.16.0.142 port 8080 and a local VLAN IP of 1.2.3.4:
98 ovs-vlan-test 172.16.0.142:8080 1.2.3.4
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102 ovs-vswitchd(8), ovs-ofctl(8), ovs-vsctl(8), ovs-test, ethtool(8), un‐
103 ame(1)
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106 The Open vSwitch Development Community
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109 2021, The Open vSwitch Development Community
1102.15 Feb 21, 2021 OVS-VLAN-TEST(8)