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Merge "Improve wording in section Modular Layer 2 configuration options"

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Jenkins 2014-10-31 08:12:23 +00:00 committed by Gerrit Code Review
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doc/config-reference/networking/section_networking-plugins-ml2.xml
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@ -10,33 +10,28 @@
components separately. This section describes these
configuration options.</para>
<note>
<title>MTU bug with VXLAN tunnelling</title>
<para>Due to a bug in Linux Bridge software maximum
transmission unit (MTU) handling, using VXLAN tunnels does
not work by default.</para>
<title>Configure MTU for VXLAN tunnelling</title>
<para>Specific MTU configuration is necessary for VXLAN to function
as expected:</para>
<itemizedlist>
<listitem>
<para>A simple workaround is to increase the MTU value
of the physical interface and physical switch
fabric by at least 50 bytes. For example, increase
the MTU value to 1550. This value enables an
automatic 50-byte MTU difference between the
physical interface (1500) and the VXLAN interface
(automatically 1500-50 = 1450). An MTU value of
1450 causes issues when virtual machine taps are
configured at an MTU value of 1500.</para>
<para>One option is to increase the MTU value of the physical
interface and physical switch fabric by at least 50 bytes.
For example, increase the MTU value to 1550. This value
enables an automatic 50-byte MTU difference between the
physical interface (1500) and the VXLAN interface
(automatically 1500-50 = 1450). An MTU value of 1450 causes
issues when virtual machine taps are configured at an MTU
value of 1500.</para>
</listitem>
<listitem>
<para>Another workaround is to decrease the virtual
Ethernet devices' MTU. Set the
<option>network_device_mtu</option> option to
1450 in the <filename>neutron.conf</filename>
file, and set all guest virtual machines' MTU to
the same value by using a DHCP option. For
information about how to use this option, see
<link
xlink:href="http://docs.openstack.org/admin-guide-cloud/content/ch_networking.html#openvswitch_plugin"
>Configure OVS plug-in</link>.</para>
<para>Another option is to decrease the virtual ethernet
devices' MTU. Set the <option>network_device_mtu</option>
option to 1450 in the <filename>neutron.conf</filename> file,
and set all guest virtual machines' MTU to the same value by
using a DHCP option. For information about how to use this
option, see <link xlink:href="http://docs.openstack.org/admin-guide-cloud/content/ch_networking.html#openvswitch_plugin">
Configure OVS plug-in</link>.</para>
</listitem>
</itemizedlist>
</note>