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<refentry id="systemd.netdev" conditional='ENABLE_NETWORKD'>
<refentryinfo>
<title>systemd.network</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Tom</firstname>
<surname>Gundersen</surname>
<email>teg@jklm.no</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>systemd.netdev</refentrytitle>
<manvolnum>5</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd.netdev</refname>
<refpurpose>Virtual Network Device configuration</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename><replaceable>netdev</replaceable>.netdev</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>Network setup is performed by
<citerefentry><refentrytitle>systemd-networkd</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
</para>
<para>The main Virtual Network Device file must have the extension <filename>.netdev</filename>;
other extensions are ignored. Virtual network devices are created as soon as networkd is
started. If a netdev with the specified name already exists, networkd will use that as-is rather
than create its own. Note that the settings of the pre-existing netdev will not be changed by
networkd.</para>
<para>The <filename>.netdev</filename> files are read from the files located in the system
network directory <filename>/usr/lib/systemd/network</filename>, the volatile runtime network
directory <filename>/run/systemd/network</filename> and the local administration network
directory <filename>/etc/systemd/network</filename>. All configuration files are collectively
sorted and processed in lexical order, regardless of the directories in which they live.
However, files with identical filenames replace each other. Files in <filename>/etc</filename>
have the highest priority, files in <filename>/run</filename> take precedence over files with
the same name in <filename>/usr/lib</filename>. This can be used to override a system-supplied
configuration file with a local file if needed. As a special case, an empty file (file size 0)
or symlink with the same name pointing to <filename>/dev/null</filename> disables the
configuration file entirely (it is "masked").</para>
<para>Along with the netdev file <filename>foo.netdev</filename>, a "drop-in" directory
<filename>foo.netdev.d/</filename> may exist. All files with the suffix <literal>.conf</literal>
from this directory will be parsed after the file itself is parsed. This is useful to alter or
add configuration settings, without having to modify the main configuration file. Each drop-in
file must have appropriate section headers.</para>
<para>In addition to <filename>/etc/systemd/network</filename>, drop-in <literal>.d</literal>
directories can be placed in <filename>/usr/lib/systemd/network</filename> or
<filename>/run/systemd/network</filename> directories. Drop-in files in
<filename>/etc</filename> take precedence over those in <filename>/run</filename> which in turn
take precedence over those in <filename>/usr/lib</filename>. Drop-in files under any of these
directories take precedence over the main netdev file wherever located. (Of course, since
<filename>/run</filename> is temporary and <filename>/usr/lib</filename> is for vendors, it is
unlikely drop-ins should be used in either of those places.)</para>
</refsect1>
<refsect1>
<title>Supported netdev kinds</title>
<para>The following kinds of virtual network devices may be
configured in <filename>.netdev</filename> files:</para>
<table>
<title>Supported kinds of virtual network devices</title>
<tgroup cols='2'>
<colspec colname='kind' />
<colspec colname='explanation' />
<thead><row>
<entry>Kind</entry>
<entry>Description</entry>
</row></thead>
<tbody>
<row><entry><varname>bond</varname></entry>
<entry>A bond device is an aggregation of all its slave devices. See <ulink url="https://www.kernel.org/doc/Documentation/networking/bonding.txt">Linux Ethernet Bonding Driver HOWTO</ulink> for details.Local configuration</entry></row>
<row><entry><varname>bridge</varname></entry>
<entry>A bridge device is a software switch, and each of its slave devices and the bridge itself are ports of the switch.</entry></row>
<row><entry><varname>dummy</varname></entry>
<entry>A dummy device drops all packets sent to it.</entry></row>
<row><entry><varname>gre</varname></entry>
<entry>A Level 3 GRE tunnel over IPv4. See <ulink url="https://tools.ietf.org/html/rfc2784">RFC 2784</ulink> for details.</entry></row>
<row><entry><varname>gretap</varname></entry>
<entry>A Level 2 GRE tunnel over IPv4.</entry></row>
<row><entry><varname>ip6gre</varname></entry>
<entry>A Level 3 GRE tunnel over IPv6.</entry></row>
<row><entry><varname>ip6tnl</varname></entry>
<entry>An IPv4 or IPv6 tunnel over IPv6</entry></row>
<row><entry><varname>ip6gretap</varname></entry>
<entry>A Level 2 GRE tunnel over IPv6.</entry></row>
<row><entry><varname>ipip</varname></entry>
<entry>An IPv4 over IPv4 tunnel.</entry></row>
<row><entry><varname>ipvlan</varname></entry>
<entry>An ipvlan device is a stacked device which receives packets from its underlying device based on IP address filtering.</entry></row>
<row><entry><varname>macvlan</varname></entry>
<entry>A macvlan device is a stacked device which receives packets from its underlying device based on MAC address filtering.</entry></row>
<row><entry><varname>macvtap</varname></entry>
<entry>A macvtap device is a stacked device which receives packets from its underlying device based on MAC address filtering.</entry></row>
<row><entry><varname>sit</varname></entry>
<entry>An IPv6 over IPv4 tunnel.</entry></row>
<row><entry><varname>tap</varname></entry>
<entry>A persistent Level 2 tunnel between a network device and a device node.</entry></row>
<row><entry><varname>tun</varname></entry>
<entry>A persistent Level 3 tunnel between a network device and a device node.</entry></row>
<row><entry><varname>veth</varname></entry>
<entry>An Ethernet tunnel between a pair of network devices.</entry></row>
<row><entry><varname>vlan</varname></entry>
<entry>A VLAN is a stacked device which receives packets from its underlying device based on VLAN tagging. See <ulink url="http://www.ieee802.org/1/pages/802.1Q.html">IEEE 802.1Q</ulink> for details.</entry></row>
<row><entry><varname>vti</varname></entry>
<entry>An IPv4 over IPSec tunnel.</entry></row>
<row><entry><varname>vti6</varname></entry>
<entry>An IPv6 over IPSec tunnel.</entry></row>
<row><entry><varname>vxlan</varname></entry>
<entry>A virtual extensible LAN (vxlan), for connecting Cloud computing deployments.</entry></row>
<row><entry><varname>geneve</varname></entry>
<entry>A GEneric NEtwork Virtualization Encapsulation (GENEVE) netdev driver.</entry></row>
<row><entry><varname>vrf</varname></entry>
<entry>A Virtual Routing and Forwarding (<ulink url="https://www.kernel.org/doc/Documentation/networking/vrf.txt">VRF</ulink>) interface to create separate routing and forwarding domains.</entry></row>
<row><entry><varname>vcan</varname></entry>
<entry>The virtual CAN driver (vcan). Similar to the network loopback devices, vcan offers a virtual local CAN interface.</entry></row>
</tbody>
</tgroup>
</table>
</refsect1>
<refsect1>
<title>[Match] Section Options</title>
<para>A virtual network device is only created if the
<literal>[Match]</literal> section matches the current
environment, or if the section is empty. The following keys are
accepted:</para>
<variablelist class='network-directives'>
<varlistentry>
<term><varname>Host=</varname></term>
<listitem>
<para>Matches against the hostname or machine ID of the
host. See <literal>ConditionHost=</literal> in
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for details.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>Virtualization=</varname></term>
<listitem>
<para>Checks whether the system is executed in a virtualized
environment and optionally test whether it is a specific
implementation. See
<literal>ConditionVirtualization=</literal> in
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for details.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>KernelCommandLine=</varname></term>
<listitem>
<para>Checks whether a specific kernel command line option
is set (or if prefixed with the exclamation mark unset). See
<literal>ConditionKernelCommandLine=</literal> in
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for details.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>Architecture=</varname></term>
<listitem>
<para>Checks whether the system is running on a specific
architecture. See <literal>ConditionArchitecture=</literal> in
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for details.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>[NetDev] Section Options</title>
<para>The <literal>[NetDev]</literal> section accepts the
following keys:</para>
<variablelist class='network-directives'>
<varlistentry>
<term><varname>Description=</varname></term>
<listitem>
<para>A free-form description of the netdev.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>Name=</varname></term>
<listitem>
<para>The interface name used when creating the netdev.
This option is compulsory.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>Kind=</varname></term>
<listitem>
<para>The netdev kind. This option is compulsory. See the
<literal>Supported netdev kinds</literal> section for the
valid keys.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>MTUBytes=</varname></term>
<listitem>
<para>The maximum transmission unit in bytes to set for
the device. The usual suffixes K, M, G, are supported and
are understood to the base of 1024. This key is not
currently supported for <literal>tun</literal> or
<literal>tap</literal> devices.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>MACAddress=</varname></term>
<listitem>
<para>The MAC address to use for the device. If none is
given, one is generated based on the interface name and
the
<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
This key is not currently supported for
<literal>tun</literal> or <literal>tap</literal> devices.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>[Bridge] Section Options</title>
<para>The <literal>[Bridge]</literal> section only applies for
netdevs of kind <literal>bridge</literal>, and accepts the
following keys:</para>
<variablelist class='network-directives'>
<varlistentry>
<term><varname>HelloTimeSec=</varname></term>
<listitem>
<para>HelloTimeSec specifies the number of seconds between two hello packets
sent out by the root bridge and the designated bridges. Hello packets are
used to communicate information about the topology throughout the entire
bridged local area network.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>MaxAgeSec=</varname></term>
<listitem>
<para>MaxAgeSec specifies the number of seconds of maximum message age.
If the last seen (received) hello packet is more than this number of
seconds old, the bridge in question will start the takeover procedure
in attempt to become the Root Bridge itself.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ForwardDelaySec=</varname></term>
<listitem>
<para>ForwardDelaySec specifies the number of seconds spent in each
of the Listening and Learning states before the Forwarding state is entered.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>AgeingTimeSec=</varname></term>
<listitem>
<para>This specifies the number of seconds a MAC Address will be kept in
the forwarding database after having a packet received from this MAC Address.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>Priority=</varname></term>
<listitem>
<para>The priority of the bridge. An integer between 0 and 65535. A lower value
means higher priority. The bridge having the lowest priority will be elected as root bridge.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>DefaultPVID=</varname></term>
<listitem>
<para>This specifies the default port VLAN ID of a newly attached bridge port.
Set this to an integer in the range 1–4094 or <literal>none</literal> to disable the PVID.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>MulticastQuerier=</varname></term>
<listitem>
<para>A boolean. This setting controls the IFLA_BR_MCAST_QUERIER option in the kernel.
If enabled, the kernel will send general ICMP queries from a zero source address.
This feature should allow faster convergence on startup, but it causes some
multicast-aware switches to misbehave and disrupt forwarding of multicast packets.
When unset, the kernel's default setting applies.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>MulticastSnooping=</varname></term>
<listitem>
<para>A boolean. This setting controls the IFLA_BR_MCAST_SNOOPING option in the kernel.
If enabled, IGMP snooping monitors the Internet Group Management Protocol (IGMP) traffic
between hosts and multicast routers. When unset, the kernel's default setting applies.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>VLANFiltering=</varname></term>
<listitem>
<para>A boolean. This setting controls the IFLA_BR_VLAN_FILTERING option in the kernel.
If enabled, the bridge will be started in VLAN-filtering mode. When unset, the kernel's
default setting applies.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>STP=</varname></term>
<listitem>
<para>A boolean. This enables the bridge's Spanning Tree Protocol (STP). When unset,
the kernel's default setting applies.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>[VLAN] Section Options</title>
<para>The <literal>[VLAN]</literal> section only applies for
netdevs of kind <literal>vlan</literal>, and accepts the
following key:</para>
<variablelist class='network-directives'>
<varlistentry>
<term><varname>Id=</varname></term>
<listitem>
<para>The VLAN ID to use. An integer in the range 0–4094.
This option is compulsory.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>GVRP=</varname></term>
<listitem>
<para>The Generic VLAN Registration Protocol (GVRP) is a protocol that
allows automatic learning of VLANs on a network. A boolean. When unset,
the kernel's default setting applies.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>MVRP=</varname></term>
<listitem>
<para>Multiple VLAN Registration Protocol (MVRP) formerly known as GARP VLAN
Registration Protocol (GVRP) is a standards-based Layer 2 network protocol,
for automatic configuration of VLAN information on switches. It was defined
in the 802.1ak amendment to 802.1Q-2005. A boolean. When unset, the kernel's
default setting applies.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>LooseBinding=</varname></term>
<listitem>
<para>The VLAN loose binding mode, in which only the operational state is passed
from the parent to the associated VLANs, but the VLAN device state is not changed.
A boolean. When unset, the kernel's default setting applies.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ReorderHeader=</varname></term>
<listitem>
<para>The VLAN reorder header is set VLAN interfaces behave like physical interfaces.
A boolean. When unset, the kernel's default setting applies.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>[MACVLAN] Section Options</title>
<para>The <literal>[MACVLAN]</literal> section only applies for
netdevs of kind <literal>macvlan</literal>, and accepts the
following key:</para>
<variablelist class='network-directives'>
<varlistentry>
<term><varname>Mode=</varname></term>
<listitem>
<para>The MACVLAN mode to use. The supported options are
<literal>private</literal>,
<literal>vepa</literal>,
<literal>bridge</literal>, and
<literal>passthru</literal>.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>[MACVTAP] Section Options</title>
<para>The <literal>[MACVTAP]</literal> section applies for
netdevs of kind <literal>macvtap</literal> and accepts the
same key as <literal>[MACVLAN]</literal>.</para>
</refsect1>
<refsect1>
<title>[IPVLAN] Section Options</title>
<para>The <literal>[IPVLAN]</literal> section only applies for
netdevs of kind <literal>ipvlan</literal>, and accepts the
following key:</para>
<variablelist class='network-directives'>
<varlistentry>
<term><varname>Mode=</varname></term>
<listitem>
<para>The IPVLAN mode to use. The supported options are
<literal>L2</literal> and <literal>L3</literal>.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>[VXLAN] Section Options</title>
<para>The <literal>[VXLAN]</literal> section only applies for
netdevs of kind <literal>vxlan</literal>, and accepts the
following keys:</para>
<variablelist class='network-directives'>
<varlistentry>
<term><varname>Id=</varname></term>
<listitem>
<para>The VXLAN ID to use.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>Remote=</varname></term>
<listitem>
<para>Configures destination IP address.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>Local=</varname></term>
<listitem>
<para>Configures local IP address.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>TOS=</varname></term>
<listitem>
<para>The Type Of Service byte value for a vxlan interface.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>TTL=</varname></term>
<listitem>
<para>A fixed Time To Live N on Virtual eXtensible Local
Area Network packets. N is a number in the range 1–255. 0
is a special value meaning that packets inherit the TTL
value.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>MacLearning=</varname></term>
<listitem>
<para>A boolean. When true, enables dynamic MAC learning
to discover remote MAC addresses.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>FDBAgeingSec=</varname></term>
<listitem>
<para>The lifetime of Forwarding Database entry learnt by
the kernel, in seconds.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>MaximumFDBEntries=</varname></term>
<listitem>
<para>Configures maximum number of FDB entries.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ReduceARPProxy=</varname></term>
<listitem>
<para>A boolean. When true, bridge-connected VXLAN tunnel
endpoint answers ARP requests from the local bridge on behalf
of remote Distributed Overlay Virtual Ethernet
<ulink url="https://en.wikipedia.org/wiki/Distributed_Overlay_Virtual_Ethernet">
(DVOE)</ulink> clients. Defaults to false.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>L2MissNotification=</varname></term>
<listitem>
<para>A boolean. When true, enables netlink LLADDR miss
notifications.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>L3MissNotification=</varname></term>
<listitem>
<para>A boolean. When true, enables netlink IP address miss
notifications.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>RouteShortCircuit=</varname></term>
<listitem>
<para>A boolean. When true, route short circuiting is turned
on.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>UDPChecksum=</varname></term>
<listitem>
<para>A boolean. When true, transmitting UDP checksums when doing VXLAN/IPv4 is turned on.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>UDP6ZeroChecksumTx=</varname></term>
<listitem>
<para>A boolean. When true, sending zero checksums in VXLAN/IPv6 is turned on.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>UDP6ZeroChecksumRx=</varname></term>
<listitem>
<para>A boolean. When true, receiving zero checksums in VXLAN/IPv6 is turned on.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>RemoteChecksumTx=</varname></term>
<listitem>
<para>A boolean. When true, remote transmit checksum offload of VXLAN is turned on.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>RemoteChecksumRx=</varname></term>
<listitem>
<para>A boolean. When true, remote receive checksum offload in VXLAN is turned on.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>GroupPolicyExtension=</varname></term>
<listitem>
<para>A boolean. When true, it enables Group Policy VXLAN extension security label mechanism
across network peers based on VXLAN. For details about the Group Policy VXLAN, see the
<ulink url="https://tools.ietf.org/html/draft-smith-vxlan-group-policy">
VXLAN Group Policy </ulink> document. Defaults to false.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>DestinationPort=</varname></term>
<listitem>
<para>Configures the default destination UDP port on a per-device basis.
If destination port is not specified then Linux kernel default will be used.
Set destination port 4789 to get the IANA assigned value. If not set or if the
destination port is assigned the empty string the default port of 4789 is used.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>PortRange=</varname></term>
<listitem>
<para>Configures VXLAN port range. VXLAN bases source
UDP port based on flow to help the receiver to be able
to load balance based on outer header flow. It
restricts the port range to the normal UDP local
ports, and allows overriding via configuration.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>FlowLabel=</varname></term>
<listitem>
<para>Specifies the flow label to use in outgoing packets.
The valid range is 0-1048575.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>[GENEVE] Section Options</title>
<para>The <literal>[GENEVE]</literal> section only applies for
netdevs of kind <literal>geneve</literal>, and accepts the
following keys:</para>
<variablelist class='network-directives'>
<varlistentry>
<term><varname>Id=</varname></term>
<listitem>
<para>Specifies the Virtual Network Identifer (VNI) to use. Ranges [0-16777215].</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>Remote=</varname></term>
<listitem>
<para>Specifies the unicast destination IP address to use in outgoing packets.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>TOS=</varname></term>
<listitem>
<para>Specifies the TOS value to use in outgoing packets. Ranges [1-255].</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>TTL=</varname></term>
<listitem>
<para>Specifies the TTL value to use in outgoing packets. Ranges [1-255].</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>UDPChecksum=</varname></term>
<listitem>
<para>A boolean. When true, specifies if UDP checksum is calculated for transmitted packets over IPv4.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>UDP6ZeroChecksumTx=</varname></term>
<listitem>
<para>A boolean. When true, skip UDP checksum calculation for transmitted packets over IPv6.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>UDP6ZeroChecksumRx=</varname></term>
<listitem>
<para>A boolean. When true, allows incoming UDP packets over IPv6 with zero checksum field.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>DestinationPort=</varname></term>
<listitem>
<para>Specifies destination port. Defaults to 6081. If not set or assigned the empty string, the default
port of 6081 is used.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>FlowLabel=</varname></term>
<listitem>
<para>Specifies the flow label to use in outgoing packets.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>[Tunnel] Section Options</title>
<para>The <literal>[Tunnel]</literal> section only applies for
netdevs of kind
<literal>ipip</literal>,
<literal>sit</literal>,
<literal>gre</literal>,
<literal>gretap</literal>,
<literal>ip6gre</literal>,
<literal>ip6gretap</literal>,
<literal>vti</literal>,
<literal>vti6</literal>, and
<literal>ip6tnl</literal> and accepts
the following keys:</para>
<variablelist class='network-directives'>
<varlistentry>
<term><varname>Local=</varname></term>
<listitem>
<para>A static local address for tunneled packets. It must
be an address on another interface of this host.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>Remote=</varname></term>
<listitem>
<para>The remote endpoint of the tunnel.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>TOS=</varname></term>
<listitem>
<para>The Type Of Service byte value for a tunnel interface.
For details about the TOS, see the
<ulink url="http://tools.ietf.org/html/rfc1349"> Type of
Service in the Internet Protocol Suite </ulink> document.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>TTL=</varname></term>
<listitem>
<para>A fixed Time To Live N on tunneled packets. N is a
number in the range 1–255. 0 is a special value meaning that
packets inherit the TTL value. The default value for IPv4
tunnels is: inherit. The default value for IPv6 tunnels is
64.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>DiscoverPathMTU=</varname></term>
<listitem>
<para>A boolean. When true, enables Path MTU Discovery on
the tunnel.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>IPv6FlowLabel=</varname></term>
<listitem>
<para>Configures the 20-bit flow label (see <ulink url="https://tools.ietf.org/html/rfc6437">
RFC 6437</ulink>) field in the IPv6 header (see <ulink url="https://tools.ietf.org/html/rfc2460">
RFC 2460</ulink>), which is used by a node to label packets of a flow.
It is only used for IPv6 tunnels.
A flow label of zero is used to indicate packets that have
not been labeled.
It can be configured to a value in the range 0–0xFFFFF, or be
set to <literal>inherit</literal>, in which case the original flowlabel is used.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>CopyDSCP=</varname></term>
<listitem>
<para>A boolean. When true, the Differentiated Service Code
Point (DSCP) field will be copied to the inner header from
outer header during the decapsulation of an IPv6 tunnel
packet. DSCP is a field in an IP packet that enables different
levels of service to be assigned to network traffic.
Defaults to <literal>no</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>EncapsulationLimit=</varname></term>
<listitem>
<para>The Tunnel Encapsulation Limit option specifies how many additional
levels of encapsulation are permitted to be prepended to the packet.
For example, a Tunnel Encapsulation Limit option containing a limit
value of zero means that a packet carrying that option may not enter
another tunnel before exiting the current tunnel.
(see <ulink url="https://tools.ietf.org/html/rfc2473#section-4.1.1"> RFC 2473</ulink>).
The valid range is 0–255 and <literal>none</literal>. Defaults to 4.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>Key=</varname></term>
<listitem>
<para>The <varname>Key=</varname> parameter specifies the same key to use in
both directions (<varname>InputKey=</varname> and <varname>OutputKey=</varname>).
The <varname>Key=</varname> is either a number or an IPv4 address-like dotted quad.
It is used as mark-configured SAD/SPD entry as part of the lookup key (both in data
and control path) in ip xfrm (framework used to implement IPsec protocol).
See <ulink url="http://man7.org/linux/man-pages/man8/ip-xfrm.8.html">
ip-xfrm — transform configuration</ulink> for details. It is only used for VTI/VTI6
tunnels.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>InputKey=</varname></term>
<listitem>
<para>The <varname>InputKey=</varname> parameter specifies the key to use for input.
The format is same as <varname>Key=</varname>. It is only used for VTI/VTI6 tunnels.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>OutputKey=</varname></term>
<listitem>
<para>The <varname>OutputKey=</varname> parameter specifies the key to use for output.
The format is same as <varname>Key=</varname>. It is only used for VTI/VTI6 tunnels.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>Mode=</varname></term>
<listitem>
<para>An <literal>ip6tnl</literal> tunnel can be in one of three
modes
<literal>ip6ip6</literal> for IPv6 over IPv6,
<literal>ipip6</literal> for IPv4 over IPv6 or
<literal>any</literal> for either.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>[Peer] Section Options</title>
<para>The <literal>[Peer]</literal> section only applies for
netdevs of kind <literal>veth</literal> and accepts the
following keys:</para>
<variablelist class='network-directives'>
<varlistentry>
<term><varname>Name=</varname></term>
<listitem>
<para>The interface name used when creating the netdev.
This option is compulsory.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>MACAddress=</varname></term>
<listitem>
<para>The peer MACAddress, if not set, it is generated in
the same way as the MAC address of the main
interface.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>[Tun] Section Options</title>
<para>The <literal>[Tun]</literal> section only applies for
netdevs of kind <literal>tun</literal>, and accepts the following
keys:</para>
<variablelist class='network-directives'>
<varlistentry>
<term><varname>OneQueue=</varname></term>
<listitem><para>Takes a boolean argument. Configures whether
all packets are queued at the device (enabled), or a fixed
number of packets are queued at the device and the rest at the
<literal>qdisc</literal>. Defaults to
<literal>no</literal>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>MultiQueue=</varname></term>
<listitem><para>Takes a boolean argument. Configures whether
to use multiple file descriptors (queues) to parallelize
packets sending and receiving. Defaults to
<literal>no</literal>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>PacketInfo=</varname></term>
<listitem><para>Takes a boolean argument. Configures whether
packets should be prepended with four extra bytes (two flag
bytes and two protocol bytes). If disabled, it indicates that
the packets will be pure IP packets. Defaults to
<literal>no</literal>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>VNetHeader=</varname></term>
<listitem><para>Takes a boolean argument. Configures
IFF_VNET_HDR flag for a tap device. It allows sending
and receiving larger Generic Segmentation Offload (GSO)
packets. This may increase throughput significantly.
Defaults to
<literal>no</literal>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>User=</varname></term>
<listitem><para>User to grant access to the
<filename>/dev/net/tun</filename> device.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>Group=</varname></term>
<listitem><para>Group to grant access to the
<filename>/dev/net/tun</filename> device.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>[Tap] Section Options</title>
<para>The <literal>[Tap]</literal> section only applies for
netdevs of kind <literal>tap</literal>, and accepts the same keys
as the <literal>[Tun]</literal> section.</para>
</refsect1>
<refsect1>
<title>[Bond] Section Options</title>
<para>The <literal>[Bond]</literal> section accepts the following
key:</para>
<variablelist class='network-directives'>
<varlistentry>
<term><varname>Mode=</varname></term>
<listitem>
<para>Specifies one of the bonding policies. The default is
<literal>balance-rr</literal> (round robin). Possible values are
<literal>balance-rr</literal>,
<literal>active-backup</literal>,
<literal>balance-xor</literal>,
<literal>broadcast</literal>,
<literal>802.3ad</literal>,
<literal>balance-tlb</literal>, and
<literal>balance-alb</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>TransmitHashPolicy=</varname></term>
<listitem>
<para>Selects the transmit hash policy to use for slave
selection in balance-xor, 802.3ad, and tlb modes. Possible
values are
<literal>layer2</literal>,
<literal>layer3+4</literal>,
<literal>layer2+3</literal>,
<literal>encap2+3</literal>, and
<literal>encap3+4</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>LACPTransmitRate=</varname></term>
<listitem>
<para>Specifies the rate with which link partner transmits
Link Aggregation Control Protocol Data Unit packets in
802.3ad mode. Possible values are <literal>slow</literal>,
which requests partner to transmit LACPDUs every 30 seconds,
and <literal>fast</literal>, which requests partner to
transmit LACPDUs every second. The default value is
<literal>slow</literal>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>MIIMonitorSec=</varname></term>
<listitem>
<para>Specifies the frequency that Media Independent
Interface link monitoring will occur. A value of zero
disables MII link monitoring. This value is rounded down to
the nearest millisecond. The default value is 0.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>UpDelaySec=</varname></term>
<listitem>
<para>Specifies the delay before a link is enabled after a
link up status has been detected. This value is rounded down
to a multiple of MIIMonitorSec. The default value is
0.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>DownDelaySec=</varname></term>
<listitem>
<para>Specifies the delay before a link is disabled after a
link down status has been detected. This value is rounded
down to a multiple of MIIMonitorSec. The default value is
0.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>LearnPacketIntervalSec=</varname></term>
<listitem>
<para>Specifies the number of seconds between instances where the bonding
driver sends learning packets to each slave peer switch.
The valid range is 1–0x7fffffff; the default value is 1. This option
has an effect only for the balance-tlb and balance-alb modes.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>AdSelect=</varname></term>
<listitem>
<para>Specifies the 802.3ad aggregation selection logic to use. Possible values are
<literal>stable</literal>,
<literal>bandwidth</literal> and
<literal>count</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>FailOverMACPolicy=</varname></term>
<listitem>
<para>Specifies whether the active-backup mode should set all slaves to
the same MAC address at the time of enslavement or, when enabled, to perform special handling of the
bond's MAC address in accordance with the selected policy. The default policy is none.
Possible values are
<literal>none</literal>,
<literal>active</literal> and
<literal>follow</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ARPValidate=</varname></term>
<listitem>
<para>Specifies whether or not ARP probes and replies should be
validated in any mode that supports ARP monitoring, or whether
non-ARP traffic should be filtered (disregarded) for link
monitoring purposes. Possible values are
<literal>none</literal>,
<literal>active</literal>,
<literal>backup</literal> and
<literal>all</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ARPIntervalSec=</varname></term>
<listitem>
<para>Specifies the ARP link monitoring frequency in milliseconds.
A value of 0 disables ARP monitoring. The default value is 0.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ARPIPTargets=</varname></term>
<listitem>
<para>Specifies the IP addresses to use as ARP monitoring peers when
ARPIntervalSec is greater than 0. These are the targets of the ARP request
sent to determine the health of the link to the targets.
Specify these values in IPv4 dotted decimal format. At least one IP
address must be given for ARP monitoring to function. The
maximum number of targets that can be specified is 16. The
default value is no IP addresses.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ARPAllTargets=</varname></term>
<listitem>
<para>Specifies the quantity of ARPIPTargets that must be reachable
in order for the ARP monitor to consider a slave as being up.
This option affects only active-backup mode for slaves with
ARPValidate enabled. Possible values are
<literal>any</literal> and
<literal>all</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>PrimaryReselectPolicy=</varname></term>
<listitem>
<para>Specifies the reselection policy for the primary slave. This
affects how the primary slave is chosen to become the active slave
when failure of the active slave or recovery of the primary slave
occurs. This option is designed to prevent flip-flopping between
the primary slave and other slaves. Possible values are
<literal>always</literal>,
<literal>better</literal> and
<literal>failure</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ResendIGMP=</varname></term>
<listitem>
<para>Specifies the number of IGMP membership reports to be issued after
a failover event. One membership report is issued immediately after
the failover, subsequent packets are sent in each 200ms interval.
The valid range is 0–255. Defaults to 1. A value of 0
prevents the IGMP membership report from being issued in response
to the failover event.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>PacketsPerSlave=</varname></term>
<listitem>
<para>Specify the number of packets to transmit through a slave before
moving to the next one. When set to 0, then a slave is chosen at
random. The valid range is 0–65535. Defaults to 1. This option
only has effect when in balance-rr mode.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>GratuitousARP=</varname></term>
<listitem>
<para>Specify the number of peer notifications (gratuitous ARPs and
unsolicited IPv6 Neighbor Advertisements) to be issued after a
failover event. As soon as the link is up on the new slave,
a peer notification is sent on the bonding device and each
VLAN sub-device. This is repeated at each link monitor interval
(ARPIntervalSec or MIIMonitorSec, whichever is active) if the number is
greater than 1. The valid range is 0–255. The default value is 1.
These options affect only the active-backup mode.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>AllSlavesActive=</varname></term>
<listitem>
<para>A boolean. Specifies that duplicate frames (received on inactive ports)
should be dropped when false, or delivered when true. Normally, bonding will drop
duplicate frames (received on inactive ports), which is desirable for
most users. But there are some times it is nice to allow duplicate
frames to be delivered. The default value is false (drop duplicate frames
received on inactive ports).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>MinLinks=</varname></term>
<listitem>
<para>Specifies the minimum number of links that must be active before
asserting carrier. The default value is 0.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ActiveSlave=</varname></term>
<listitem>
<para>A boolean. Specifies the new active slave. The <literal>ActiveSlave=</literal>
option is only valid for following modes:
<literal>active-backup</literal>,
<literal>balance-alb</literal> and
<literal>balance-tlb</literal>. Defaults to false.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>PrimarySlave=</varname></term>
<listitem>
<para>A boolean. Specifies which slave is the primary device. The specified
device will always be the active slave while it is available. Only when the
primary is off-line will alternate devices be used. This is useful when
one slave is preferred over another, e.g. when one slave has higher throughput
than another. The <literal>PrimarySlave=</literal> option is only valid for
following modes:
<literal>active-backup</literal>,
<literal>balance-alb</literal> and
<literal>balance-tlb</literal>. Defaults to false.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>For more detail information see
<ulink url="https://www.kernel.org/doc/Documentation/networking/bonding.txt">
Linux Ethernet Bonding Driver HOWTO</ulink></para>
</refsect1>
<refsect1>
<title>Example</title>
<example>
<title>/etc/systemd/network/25-bridge.netdev</title>
<programlisting>[NetDev]
Name=bridge0
Kind=bridge</programlisting>
</example>
<example>
<title>/etc/systemd/network/25-vlan1.netdev</title>
<programlisting>[Match]
Virtualization=no
[NetDev]
Name=vlan1
Kind=vlan
[VLAN]
Id=1</programlisting>
</example>
<example>
<title>/etc/systemd/network/25-ipip.netdev</title>
<programlisting>[NetDev]
Name=ipip-tun
Kind=ipip
MTUBytes=1480
[Tunnel]
Local=192.168.223.238
Remote=192.169.224.239
TTL=64</programlisting>
</example>
<example>
<title>/etc/systemd/network/25-tap.netdev</title>
<programlisting>[NetDev]
Name=tap-test
Kind=tap
[Tap]
MultiQueue=true
PacketInfo=true</programlisting> </example>
<example>
<title>/etc/systemd/network/25-sit.netdev</title>
<programlisting>[NetDev]
Name=sit-tun
Kind=sit
MTUBytes=1480
[Tunnel]
Local=10.65.223.238
Remote=10.65.223.239</programlisting>
</example>
<example>
<title>/etc/systemd/network/25-gre.netdev</title>
<programlisting>[NetDev]
Name=gre-tun
Kind=gre
MTUBytes=1480
[Tunnel]
Local=10.65.223.238
Remote=10.65.223.239</programlisting>
</example>
<example>
<title>/etc/systemd/network/25-vti.netdev</title>
<programlisting>[NetDev]
Name=vti-tun
Kind=vti
MTUBytes=1480
[Tunnel]
Local=10.65.223.238
Remote=10.65.223.239</programlisting>
</example>
<example>
<title>/etc/systemd/network/25-veth.netdev</title>
<programlisting>[NetDev]
Name=veth-test
Kind=veth
[Peer]
Name=veth-peer</programlisting>
</example>
<example>
<title>/etc/systemd/network/25-bond.netdev</title>
<programlisting>[NetDev]
Name=bond1
Kind=bond
[Bond]
Mode=802.3ad
TransmitHashPolicy=layer3+4
MIIMonitorSec=1s
LACPTransmitRate=fast
</programlisting>
</example>
<example>
<title>/etc/systemd/network/25-dummy.netdev</title>
<programlisting>[NetDev]
Name=dummy-test
Kind=dummy
MACAddress=12:34:56:78:9a:bc</programlisting>
</example>
<example>
<title>/etc/systemd/network/25-vrf.netdev</title>
<para>Create a VRF interface with table 42.</para>
<programlisting>[NetDev]
Name=vrf-test
Kind=vrf
[VRF]
TableId=42</programlisting>
</example>
<example>
<title>/etc/systemd/network/25-macvtap.netdev</title>
<para>Create a MacVTap device.</para>
<programlisting>[NetDev]
Name=macvtap-test
Kind=macvtap
</programlisting>
</example>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-networkd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>