man/systemd.network.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="systemd.network" conditional='ENABLE_NETWORKD'>
   7
   8   <refentryinfo>
   9     <title>systemd.network</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>systemd.network</refentrytitle>
  15     <manvolnum>5</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>systemd.network</refname>
  20     <refpurpose>Network configuration</refpurpose>
  21   </refnamediv>
  22
  23   <refsynopsisdiv>
  24     <para><filename><replaceable>network</replaceable>.network</filename></para>
  25   </refsynopsisdiv>
  26
  27   <refsect1>
  28     <title>Description</title>
  29
  30     <para>Network setup is performed by
  31     <citerefentry><refentrytitle>systemd-networkd</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
  32     </para>
  33
  34     <para>The main network file must have the extension <filename>.network</filename>; other
  35     extensions are ignored. Networks are applied to links whenever the links appear.</para>
  36
  37     <para>The <filename>.network</filename> files are read from the files located in the system network
  38     directories <filename>/usr/lib/systemd/network</filename> and
  39     <filename>/usr/local/lib/systemd/network</filename>, the volatile runtime network directory
  40     <filename>/run/systemd/network</filename> and the local administration network directory
  41     <filename>/etc/systemd/network</filename>. All configuration files are collectively sorted and processed
  42     in lexical order, regardless of the directories in which they live. However, files with identical
  43     filenames replace each other. Files in <filename>/etc</filename> have the highest priority, files in
  44     <filename>/run</filename> take precedence over files with the same name under
  45     <filename>/usr</filename>. This can be used to override a system-supplied configuration file with a local
  46     file if needed. As a special case, an empty file (file size 0) or symlink with the same name pointing to
  47     <filename>/dev/null</filename> disables the configuration file entirely (it is "masked").</para>
  48
  49     <para>Along with the network file <filename>foo.network</filename>, a "drop-in" directory
  50     <filename>foo.network.d/</filename> may exist. All files with the suffix
  51     <literal>.conf</literal> from this directory will be parsed after the file itself is
  52     parsed. This is useful to alter or add configuration settings, without having to modify the main
  53     configuration file. Each drop-in file must have appropriate section headers.</para>
  54
  55     <para>In addition to <filename>/etc/systemd/network</filename>, drop-in <literal>.d</literal>
  56     directories can be placed in <filename>/usr/lib/systemd/network</filename> or
  57     <filename>/run/systemd/network</filename> directories. Drop-in files in
  58     <filename>/etc</filename> take precedence over those in <filename>/run</filename> which in turn
  59     take precedence over those in <filename>/usr/lib</filename>. Drop-in files under any of these
  60     directories take precedence over the main netdev file wherever located.</para>
  61
  62     <para>Note that an interface without any static IPv6 addresses configured, and neither DHCPv6
  63     nor IPv6LL enabled, shall be considered to have no IPv6 support. IPv6 will be automatically
  64     disabled for that interface by writing "1" to
  65     <filename>/proc/sys/net/ipv6/conf/<replaceable>ifname</replaceable>/disable_ipv6</filename>.
  66     </para>
  67   </refsect1>
  68
  69   <refsect1>
  70     <title>[Match] Section Options</title>
  71
  72       <para>The network file contains a <literal>[Match]</literal>
  73       section, which determines if a given network file may be applied
  74       to a given device; and a <literal>[Network]</literal> section
  75       specifying how the device should be configured. The first (in
  76       lexical order) of the network files that matches a given device
  77       is applied, all later files are ignored, even if they match as
  78       well.</para>
  79
  80       <para>A network file is said to match a device if each of the
  81       entries in the <literal>[Match]</literal> section matches, or if
  82       the section is empty. The following keys are accepted:</para>
  83
  84       <variablelist class='network-directives'>
  85         <varlistentry>
  86           <term><varname>MACAddress=</varname></term>
  87           <listitem>
  88             <para>A whitespace-separated list of hardware addresses. Use full colon-, hyphen- or dot-delimited hexadecimal. See the example below.
  89             This option may appear more than one, in which case the lists are merged. If the empty string is assigned to this option, the list
  90             of hardware addresses defined prior to this is reset.</para>
  91
  92             <para>Example:
  93             <programlisting>MACAddress=01:23:45:67:89:ab 00-11-22-33-44-55 AABB.CCDD.EEFF</programlisting></para>
  94           </listitem>
  95         </varlistentry>
  96         <varlistentry>
  97           <term><varname>Path=</varname></term>
  98           <listitem>
  99             <para>A whitespace-separated list of shell-style globs
 100             matching the persistent path, as exposed by the udev
 101             property <literal>ID_PATH</literal>. If the list is
 102             prefixed with a "!", the test is inverted; i.e. it is
 103             true when <literal>ID_PATH</literal> does not match any
 104             item in the list.</para>
 105           </listitem>
 106         </varlistentry>
 107         <varlistentry>
 108           <term><varname>Driver=</varname></term>
 109           <listitem>
 110             <para>A whitespace-separated list of shell-style globs
 111             matching the driver currently bound to the device, as
 112             exposed by the udev property <literal>DRIVER</literal>
 113             of its parent device, or if that is not set the driver
 114             as exposed by <literal>ethtool -i</literal> of the
 115             device itself. If the list is prefixed with a "!", the
 116             test is inverted.</para>
 117           </listitem>
 118         </varlistentry>
 119         <varlistentry>
 120           <term><varname>Type=</varname></term>
 121           <listitem>
 122             <para>A whitespace-separated list of shell-style globs
 123             matching the device type, as exposed by the udev property
 124             <literal>DEVTYPE</literal>. If the list is prefixed with
 125             a "!", the test is inverted.</para>
 126           </listitem>
 127         </varlistentry>
 128         <varlistentry>
 129           <term><varname>Name=</varname></term>
 130           <listitem>
 131             <para>A whitespace-separated list of shell-style globs
 132             matching the device name, as exposed by the udev property
 133             <literal>INTERFACE</literal>. If the list is prefixed
 134             with a "!", the test is inverted.</para>
 135           </listitem>
 136         </varlistentry>
 137         <varlistentry>
 138           <term><varname>Host=</varname></term>
 139           <listitem>
 140             <para>Matches against the hostname or machine ID of the
 141             host. See <literal>ConditionHost=</literal> in
 142             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 143             for details.
 144             </para>
 145           </listitem>
 146         </varlistentry>
 147         <varlistentry>
 148           <term><varname>Virtualization=</varname></term>
 149           <listitem>
 150             <para>Checks whether the system is executed in a virtualized
 151             environment and optionally test whether it is a specific
 152             implementation. See <literal>ConditionVirtualization=</literal> in
 153             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 154             for details.
 155             </para>
 156           </listitem>
 157         </varlistentry>
 158         <varlistentry>
 159           <term><varname>KernelCommandLine=</varname></term>
 160           <listitem>
 161             <para>Checks whether a specific kernel command line option is
 162             set (or if prefixed with the exclamation mark unset). See
 163             <literal>ConditionKernelCommandLine=</literal> in
 164             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 165             for details.
 166             </para>
 167           </listitem>
 168         </varlistentry>
 169         <varlistentry>
 170           <term><varname>KernelVersion=</varname></term>
 171           <listitem>
 172             <para>Checks whether the kernel version (as reported by <command>uname -r</command>) matches a certain
 173             expression (or if prefixed with the exclamation mark does not match it). See
 174             <literal>ConditionKernelVersion=</literal> in
 175             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 176             details.
 177             </para>
 178           </listitem>
 179         </varlistentry>
 180         <varlistentry>
 181           <term><varname>Architecture=</varname></term>
 182           <listitem>
 183             <para>Checks whether the system is running on a specific
 184             architecture. See <literal>ConditionArchitecture=</literal> in
 185             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 186             for details.
 187             </para>
 188           </listitem>
 189         </varlistentry>
 190       </variablelist>
 191
 192   </refsect1>
 193
 194   <refsect1>
 195     <title>[Link] Section Options</title>
 196
 197     <para> The <literal>[Link]</literal> section accepts the following keys:</para>
 198
 199     <variablelist class='network-directives'>
 200       <varlistentry>
 201         <term><varname>MACAddress=</varname></term>
 202         <listitem>
 203           <para>The hardware address to set for the device.</para>
 204         </listitem>
 205       </varlistentry>
 206       <varlistentry>
 207         <term><varname>MTUBytes=</varname></term>
 208         <listitem>
 209           <para>The maximum transmission unit in bytes to set for the
 210           device. The usual suffixes K, M, G, are supported and are
 211           understood to the base of 1024.</para>
 212           <para>Note that if IPv6 is enabled on the interface, and the MTU is chosen
 213           below 1280 (the minimum MTU for IPv6) it will automatically be increased to this value.</para>
 214         </listitem>
 215       </varlistentry>
 216       <varlistentry>
 217         <term><varname>ARP=</varname></term>
 218         <listitem>
 219           <para>Takes a boolean. If set to true, the ARP (low-level Address Resolution Protocol)
 220           for this interface is enabled. When unset, the kernel's default will be used.</para>
 221           <para> For example, disabling ARP is useful when creating multiple MACVLAN or VLAN virtual
 222           interfaces atop a single lower-level physical interface, which will then only serve as a
 223           link/"bridge" device aggregating traffic to the same physical link and not participate in
 224           the network otherwise.</para>
 225         </listitem>
 226       </varlistentry>
 227       <varlistentry>
 228         <term><varname>Multicast=</varname></term>
 229         <listitem>
 230           <para>Takes a boolean. If set to true, the multicast flag on the device is enabled.</para>
 231         </listitem>
 232       </varlistentry>
 233       <varlistentry>
 234         <term><varname>AllMulticast=</varname></term>
 235         <listitem>
 236           <para>Takes a boolean. If set to true, the driver retrieves all multicast packets from the network.
 237           This happens when multicast routing is enabled.</para>
 238         </listitem>
 239       </varlistentry>
 240       <varlistentry>
 241         <term><varname>Unmanaged=</varname></term>
 242         <listitem>
 243           <para>Takes a boolean. When <literal>yes</literal>, no attempts are
 244           made to bring up or configure matching links, equivalent to
 245           when there are no matching network files. Defaults to
 246           <literal>no</literal>.</para>
 247           <para>This is useful for preventing later matching network
 248           files from interfering with certain interfaces that are fully
 249           controlled by other applications.</para>
 250         </listitem>
 251       </varlistentry>
 252       <varlistentry>
 253         <term><varname>RequiredForOnline=</varname></term>
 254         <listitem>
 255           <para>Takes a boolean or operational state. Please see
 256           <citerefentry><refentrytitle>networkctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 257           for possible operational states. When <literal>yes</literal>, the network is deemed required when
 258           determining whether the system is online when running
 259           <command>systemd-networkd-wait-online</command>. When <literal>no</literal>, the network is ignored
 260           when checking for online state. When an operational state is set, <literal>yes</literal> is implied,
 261           and this controls the operational state required for the network interface to be considered online.
 262           Defaults to <literal>yes</literal>.</para>
 263
 264           <para>The network will be brought up normally in all cases, but in
 265           the event that there is no address being assigned by DHCP or the
 266           cable is not plugged in, the link will simply remain offline and be
 267           skipped automatically by <command>systemd-networkd-wait-online</command>
 268           if <literal>RequiredForOnline=no</literal>.</para>
 269         </listitem>
 270       </varlistentry>
 271     </variablelist>
 272   </refsect1>
 273
 274   <refsect1>
 275     <title>[Network] Section Options</title>
 276
 277       <para>The <literal>[Network]</literal> section accepts the following keys:</para>
 278
 279       <variablelist class='network-directives'>
 280         <varlistentry>
 281           <term><varname>Description=</varname></term>
 282           <listitem>
 283             <para>A description of the device. This is only used for
 284             presentation purposes.</para>
 285           </listitem>
 286         </varlistentry>
 287         <varlistentry>
 288           <term><varname>DHCP=</varname></term>
 289           <listitem>
 290             <para>Enables DHCPv4 and/or DHCPv6 client support. Accepts
 291             <literal>yes</literal>, <literal>no</literal>,
 292             <literal>ipv4</literal>, or <literal>ipv6</literal>. Defaults
 293             to <literal>no</literal>.</para>
 294
 295             <para>Note that DHCPv6 will by default be triggered by Router
 296             Advertisement, if that is enabled, regardless of this parameter.
 297             By enabling DHCPv6 support explicitly, the DHCPv6 client will
 298             be started regardless of the presence of routers on the link,
 299             or what flags the routers pass. See
 300             <literal>IPv6AcceptRA=</literal>.</para>
 301
 302             <para>Furthermore, note that by default the domain name
 303             specified through DHCP is not used for name resolution.
 304             See option <option>UseDomains=</option> below.</para>
 305
 306             <para>See the <literal>[DHCP]</literal> section below for further configuration options for the DHCP client
 307             support.</para>
 308           </listitem>
 309         </varlistentry>
 310         <varlistentry>
 311           <term><varname>DHCPServer=</varname></term>
 312           <listitem>
 313             <para>Takes a boolean. If set to <literal>yes</literal>, DHCPv4 server will be started. Defaults
 314             to <literal>no</literal>. Further settings for the DHCP
 315             server may be set in the <literal>[DHCPServer]</literal>
 316             section described below.</para>
 317           </listitem>
 318         </varlistentry>
 319         <varlistentry>
 320           <term><varname>LinkLocalAddressing=</varname></term>
 321           <listitem>
 322             <para>Enables link-local address autoconfiguration. Accepts <literal>yes</literal>,
 323             <literal>no</literal>, <literal>ipv4</literal>, or <literal>ipv6</literal>. If
 324             <varname>Bridge=</varname> is set, defaults to <literal>no</literal>, and if not,
 325             defaults to <literal>ipv6</literal>.</para>
 326           </listitem>
 327         </varlistentry>
 328         <varlistentry>
 329           <term><varname>IPv4LLRoute=</varname></term>
 330           <listitem>
 331             <para>Takes a boolean. If set to true, sets up the route needed for
 332             non-IPv4LL hosts to communicate with IPv4LL-only hosts. Defaults
 333             to false.
 334             </para>
 335           </listitem>
 336         </varlistentry>
 337         <varlistentry>
 338           <term><varname>IPv6Token=</varname></term>
 339           <listitem>
 340             <para>An IPv6 address with the top 64 bits unset. When set, indicates the
 341             64-bit interface part of SLAAC IPv6 addresses for this link. Note that
 342             the token is only ever used for SLAAC, and not for DHCPv6 addresses, even
 343             in the case DHCP is requested by router advertisement. By default, the
 344             token is autogenerated.</para>
 345           </listitem>
 346         </varlistentry>
 347         <varlistentry>
 348           <term><varname>LLMNR=</varname></term>
 349           <listitem>
 350             <para>Takes a boolean or <literal>resolve</literal>. When true,
 351             enables <ulink
 352             url="https://tools.ietf.org/html/rfc4795">Link-Local
 353             Multicast Name Resolution</ulink> on the link. When set to
 354             <literal>resolve</literal>, only resolution is enabled,
 355             but not host registration and announcement. Defaults to
 356             true. This setting is read by
 357             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 358           </listitem>
 359         </varlistentry>
 360         <varlistentry>
 361           <term><varname>MulticastDNS=</varname></term>
 362           <listitem>
 363             <para>Takes a boolean or <literal>resolve</literal>. When true,
 364             enables <ulink
 365             url="https://tools.ietf.org/html/rfc6762">Multicast
 366             DNS</ulink> support on the link. When set to
 367             <literal>resolve</literal>, only resolution is enabled,
 368             but not host or service registration and
 369             announcement. Defaults to false. This setting is read by
 370             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 371           </listitem>
 372         </varlistentry>
 373         <varlistentry>
 374           <term><varname>DNSOverTLS=</varname></term>
 375           <listitem>
 376             <para>Takes false or
 377             <literal>opportunistic</literal>. When set to <literal>opportunistic</literal>, enables
 378             <ulink
 379             url="https://tools.ietf.org/html/rfc7858">DNS-over-TLS</ulink>
 380             support on the link. This option defines a
 381             per-interface setting for
 382             <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>'s
 383             global <varname>DNSOverTLS=</varname> option. Defaults to
 384             false. This setting is read by
 385             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 386           </listitem>
 387         </varlistentry>
 388         <varlistentry>
 389           <term><varname>DNSSEC=</varname></term>
 390           <listitem>
 391             <para>Takes a boolean. or
 392             <literal>allow-downgrade</literal>. When true, enables
 393             <ulink
 394             url="https://tools.ietf.org/html/rfc4033">DNSSEC</ulink>
 395             DNS validation support on the link. When set to
 396             <literal>allow-downgrade</literal>, compatibility with
 397             non-DNSSEC capable networks is increased, by automatically
 398             turning off DNSSEC in this case. This option defines a
 399             per-interface setting for
 400             <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>'s
 401             global <varname>DNSSEC=</varname> option. Defaults to
 402             false. This setting is read by
 403             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 404           </listitem>
 405         </varlistentry>
 406         <varlistentry>
 407           <term><varname>DNSSECNegativeTrustAnchors=</varname></term>
 408           <listitem><para>A space-separated list of DNSSEC negative
 409           trust anchor domains. If specified and DNSSEC is enabled,
 410           look-ups done via the interface's DNS server will be subject
 411           to the list of negative trust anchors, and not require
 412           authentication for the specified domains, or anything below
 413           it. Use this to disable DNSSEC authentication for specific
 414           private domains, that cannot be proven valid using the
 415           Internet DNS hierarchy. Defaults to the empty list. This
 416           setting is read by
 417           <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 418           </listitem>
 419         </varlistentry>
 420         <varlistentry>
 421           <term><varname>LLDP=</varname></term>
 422           <listitem>
 423             <para>Controls support for Ethernet LLDP packet reception. LLDP is a link-layer protocol commonly
 424             implemented on professional routers and bridges which announces which physical port a system is connected
 425             to, as well as other related data. Accepts a boolean or the special value
 426             <literal>routers-only</literal>. When true, incoming LLDP packets are accepted and a database of all LLDP
 427             neighbors maintained. If <literal>routers-only</literal> is set only LLDP data of various types of routers
 428             is collected and LLDP data about other types of devices ignored (such as stations, telephones and
 429             others). If false, LLDP reception is disabled. Defaults to <literal>routers-only</literal>. Use
 430             <citerefentry><refentrytitle>networkctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> to query the
 431             collected neighbor data. LLDP is only available on Ethernet links. See <varname>EmitLLDP=</varname> below
 432             for enabling LLDP packet emission from the local system.
 433             </para>
 434           </listitem>
 435         </varlistentry>
 436         <varlistentry>
 437           <term><varname>EmitLLDP=</varname></term>
 438           <listitem>
 439             <para>Controls support for Ethernet LLDP packet emission. Accepts a boolean parameter or the special values
 440             <literal>nearest-bridge</literal>, <literal>non-tpmr-bridge</literal> and
 441             <literal>customer-bridge</literal>.  Defaults to false, which turns off LLDP packet emission. If not false,
 442             a short LLDP packet with information about the local system is sent out in regular intervals on the
 443             link. The LLDP packet will contain information about the local host name, the local machine ID (as stored
 444             in <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>) and the
 445             local interface name, as well as the pretty hostname of the system (as set in
 446             <citerefentry><refentrytitle>machine-info</refentrytitle><manvolnum>5</manvolnum></citerefentry>). LLDP
 447             emission is only available on Ethernet links. Note that this setting passes data suitable for
 448             identification of host to the network and should thus not be enabled on untrusted networks, where such
 449             identification data should not be made available. Use this option to permit other systems to identify on
 450             which interfaces they are connected to this system. The three special values control propagation of the
 451             LLDP packets. The <literal>nearest-bridge</literal> setting permits propagation only to the nearest
 452             connected bridge, <literal>non-tpmr-bridge</literal> permits propagation across Two-Port MAC Relays, but
 453             not any other bridges, and <literal>customer-bridge</literal> permits propagation until a customer bridge
 454             is reached. For details about these concepts, see <ulink
 455             url="https://standards.ieee.org/findstds/standard/802.1AB-2016.html">IEEE 802.1AB-2016</ulink>. Note that
 456             configuring this setting to true is equivalent to <literal>nearest-bridge</literal>, the recommended and
 457             most restricted level of propagation. See <varname>LLDP=</varname> above for an option to enable LLDP
 458             reception.</para>
 459           </listitem>
 460         </varlistentry>
 461         <varlistentry>
 462           <term><varname>BindCarrier=</varname></term>
 463           <listitem>
 464             <para>A link name or a list of link names. When set, controls the behavior of the current
 465             link. When all links in the list are in an operational down state, the current link is brought
 466             down. When at least one link has carrier, the current interface is brought up.
 467             </para>
 468           </listitem>
 469         </varlistentry>
 470         <varlistentry>
 471           <term><varname>Address=</varname></term>
 472           <listitem>
 473             <para>A static IPv4 or IPv6 address and its prefix length,
 474             separated by a <literal>/</literal> character. Specify
 475             this key more than once to configure several addresses.
 476             The format of the address must be as described in
 477             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 478             This is a short-hand for an [Address] section only
 479             containing an Address key (see below). This option may be
 480             specified more than once.
 481             </para>
 482
 483             <para>If the specified address is <literal>0.0.0.0</literal> (for IPv4) or <literal>::</literal>
 484             (for IPv6), a new address range of the requested size is automatically allocated from a
 485             system-wide pool of unused ranges. Note that the prefix length must be equal or larger than 8 for
 486             IPv4, and 64 for IPv6. The allocated range is checked against all current network interfaces and
 487             all known network configuration files to avoid address range conflicts. The default system-wide
 488             pool consists of 192.168.0.0/16, 172.16.0.0/12 and 10.0.0.0/8 for IPv4, and fd00::/8 for IPv6.
 489             This functionality is useful to manage a large number of dynamically created network interfaces
 490             with the same network configuration and automatic address range assignment.</para>
 491
 492           </listitem>
 493         </varlistentry>
 494         <varlistentry>
 495           <term><varname>Gateway=</varname></term>
 496           <listitem>
 497             <para>The gateway address, which must be in the format
 498             described in
 499             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 500             This is a short-hand for a [Route] section only containing
 501             a Gateway key. This option may be specified more than
 502             once.</para>
 503           </listitem>
 504         </varlistentry>
 505         <varlistentry>
 506           <term><varname>DNS=</varname></term>
 507           <listitem>
 508             <para>A DNS server address, which must be in the format
 509             described in
 510             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 511             This option may be specified more than once. This setting is read by
 512             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 513           </listitem>
 514         </varlistentry>
 515         <varlistentry>
 516           <term><varname>Domains=</varname></term>
 517           <listitem>
 518             <para>A list of domains which should be resolved using the DNS servers on this link. Each item in the list
 519             should be a domain name, optionally prefixed with a tilde (<literal>~</literal>). The domains with the
 520             prefix are called "routing-only domains". The domains without the prefix are called "search domains" and
 521             are first used as search suffixes for extending single-label host names (host names containing no dots) to
 522             become fully qualified domain names (FQDNs). If a single-label host name is resolved on this interface,
 523             each of the specified search domains are appended to it in turn, converting it into a fully qualified
 524             domain name, until one of them may be successfully resolved.</para>
 525
 526             <para>Both "search" and "routing-only" domains are used for routing of DNS queries: look-ups for host names
 527             ending in those domains (hence also single label names, if any "search domains" are listed), are routed to
 528             the DNS servers configured for this interface. The domain routing logic is particularly useful on
 529             multi-homed hosts with DNS servers serving particular private DNS zones on each interface.</para>
 530
 531             <para>The "routing-only" domain <literal>~.</literal> (the tilde indicating definition of a routing domain,
 532             the dot referring to the DNS root domain which is the implied suffix of all valid DNS names) has special
 533             effect. It causes all DNS traffic which does not match another configured domain routing entry to be routed
 534             to DNS servers specified for this interface. This setting is useful to prefer a certain set of DNS servers
 535             if a link on which they are connected is available.</para>
 536
 537             <para>This setting is read by
 538             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
 539             "Search domains" correspond to the <varname>domain</varname> and <varname>search</varname> entries in
 540             <citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 541             Domain name routing has no equivalent in the traditional glibc API, which has no concept of domain
 542             name servers limited to a specific link.</para>
 543           </listitem>
 544         </varlistentry>
 545         <varlistentry>
 546           <term><varname>DNSDefaultRoute=</varname></term>
 547           <listitem>
 548             <para>Takes a boolean argument. If true, this link's configured DNS servers are used for resolving domain
 549             names that do not match any link's configured <varname>Domains=</varname> setting. If false, this link's
 550             configured DNS servers are never used for such domains, and are exclusively used for resolving names that
 551             match at least one of the domains configured on this link. If not specified defaults to an automatic mode:
 552             queries not matching any link's configured domains will be routed to this link if it has no routing-only
 553             domains configured.</para>
 554           </listitem>
 555         </varlistentry>
 556         <varlistentry>
 557           <term><varname>NTP=</varname></term>
 558           <listitem>
 559             <para>An NTP server address. This option may be specified more than once. This setting is read by
 560             <citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 561           </listitem>
 562         </varlistentry>
 563         <varlistentry>
 564           <term><varname>IPForward=</varname></term>
 565           <listitem><para>Configures IP packet forwarding for the
 566           system. If enabled, incoming packets on any network
 567           interface will be forwarded to any other interfaces
 568           according to the routing table. Takes a boolean,
 569           or the values <literal>ipv4</literal> or
 570           <literal>ipv6</literal>, which only enable IP packet
 571           forwarding for the specified address family.  This controls
 572           the <filename>net.ipv4.ip_forward</filename> and
 573           <filename>net.ipv6.conf.all.forwarding</filename> sysctl
 574           options of the network interface (see <ulink
 575           url="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">ip-sysctl.txt</ulink>
 576           for details about sysctl options). Defaults to
 577           <literal>no</literal>.</para>
 578
 579           <para>Note: this setting controls a global kernel option,
 580           and does so one way only: if a network that has this setting
 581           enabled is set up the global setting is turned on.  However,
 582           it is never turned off again, even after all networks with
 583           this setting enabled are shut down again.</para>
 584
 585           <para>To allow IP packet forwarding only between specific
 586           network interfaces use a firewall.</para>
 587           </listitem>
 588         </varlistentry>
 589         <varlistentry>
 590           <term><varname>IPMasquerade=</varname></term>
 591           <listitem><para>Configures IP masquerading for the network
 592           interface. If enabled, packets forwarded from the network
 593           interface will be appear as coming from the local host.
 594           Takes a boolean argument. Implies
 595           <varname>IPForward=ipv4</varname>. Defaults to
 596           <literal>no</literal>.</para></listitem>
 597         </varlistentry>
 598         <varlistentry>
 599           <term><varname>IPv6PrivacyExtensions=</varname></term>
 600           <listitem><para>Configures use of stateless temporary
 601           addresses that change over time (see <ulink
 602           url="https://tools.ietf.org/html/rfc4941">RFC 4941</ulink>,
 603           Privacy Extensions for Stateless Address Autoconfiguration
 604           in IPv6). Takes a boolean or the special values
 605           <literal>prefer-public</literal> and
 606           <literal>kernel</literal>. When true, enables the privacy
 607           extensions and prefers temporary addresses over public
 608           addresses. When <literal>prefer-public</literal>, enables the
 609           privacy extensions, but prefers public addresses over
 610           temporary addresses. When false, the privacy extensions
 611           remain disabled. When <literal>kernel</literal>, the kernel's
 612           default setting will be left in place.  Defaults to
 613           <literal>no</literal>.</para></listitem>
 614         </varlistentry>
 615         <varlistentry>
 616           <term><varname>IPv6AcceptRA=</varname></term>
 617           <listitem><para>Takes a boolean. Controls IPv6 Router Advertisement (RA) reception support for the interface.
 618           If true, RAs are accepted; if false, RAs are ignored, independently of the local forwarding state.
 619           If unset, the kernel's default is used, and RAs are accepted only when local forwarding
 620           is disabled for that interface.  When RAs are accepted, they may trigger the start of the DHCPv6 client if
 621           the relevant flags are set in the RA data, or if no routers are found on the link.</para>
 622
 623           <para>Further settings for the IPv6 RA support may be configured in the
 624           <literal>[IPv6AcceptRA]</literal> section, see below.</para>
 625
 626           <para>Also see <ulink
 627           url="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">ip-sysctl.txt</ulink> in the kernel
 628           documentation regarding <literal>accept_ra</literal>, but note that systemd's setting of
 629           <constant>1</constant> (i.e. true) corresponds to kernel's setting of <constant>2</constant>.</para>
 630
 631           <para>Note that if this option is enabled a userspace implementation of the IPv6 RA protocol is
 632           used, and the kernel's own implementation remains disabled, since `networkd` needs to know all
 633           details supplied in the advertisements, and these are not available from the kernel if the kernel's
 634           own implemenation is used.</para>
 635         </listitem>
 636         </varlistentry>
 637         <varlistentry>
 638           <term><varname>IPv6DuplicateAddressDetection=</varname></term>
 639           <listitem><para>Configures the amount of IPv6 Duplicate
 640           Address Detection (DAD) probes to send. When unset, the kernel's default will be used.
 641         </para></listitem>
 642         </varlistentry>
 643         <varlistentry>
 644           <term><varname>IPv6HopLimit=</varname></term>
 645           <listitem><para>Configures IPv6 Hop Limit. For each router that
 646           forwards the packet, the hop limit is decremented by 1. When the
 647           hop limit field reaches zero, the packet is discarded.
 648           When unset, the kernel's default will be used.
 649         </para></listitem>
 650         </varlistentry>
 651         <varlistentry>
 652           <term><varname>IPv4ProxyARP=</varname></term>
 653           <listitem><para>Takes a boolean. Configures proxy ARP for IPv4. Proxy ARP is the technique in which one host,
 654           usually a router, answers ARP requests intended for another machine. By "faking" its identity,
 655           the router accepts responsibility for routing packets to the "real" destination. (see <ulink
 656           url="https://tools.ietf.org/html/rfc1027">RFC 1027</ulink>.
 657           When unset, the kernel's default will be used.
 658         </para></listitem>
 659         </varlistentry>
 660         <varlistentry>
 661           <term><varname>IPv6ProxyNDP=</varname></term>
 662           <listitem><para>Takes a boolean. Configures proxy NDP for IPv6. Proxy NDP (Neighbor Discovery
 663           Protocol) is a technique for IPv6 to allow routing of addresses to a different
 664           destination when peers expect them to be present on a certain physical link.
 665           In this case a router answers Neighbour Advertisement messages intended for
 666           another machine by offering its own MAC address as destination.
 667           Unlike proxy ARP for IPv4, it is not enabled globally, but will only send Neighbour
 668           Advertisement messages for addresses in the IPv6 neighbor proxy table,
 669           which can also be shown by <command>ip -6 neighbour show proxy</command>.
 670           systemd-networkd will control the per-interface `proxy_ndp` switch for each configured
 671           interface depending on this option.
 672           When unset, the kernel's default will be used.
 673         </para></listitem>
 674         </varlistentry>
 675         <varlistentry>
 676           <term><varname>IPv6ProxyNDPAddress=</varname></term>
 677           <listitem><para>An IPv6 address, for which Neighbour Advertisement messages will be
 678           proxied. This option may be specified more than once. systemd-networkd will add the
 679           <option>IPv6ProxyNDPAddress=</option> entries to the kernel's IPv6 neighbor proxy table.
 680           This option implies <option>IPv6ProxyNDP=yes</option> but has no effect if
 681           <option>IPv6ProxyNDP</option> has been set to false. When unset, the kernel's default will be used.
 682         </para></listitem>
 683         </varlistentry>
 684         <varlistentry>
 685           <term><varname>IPv6PrefixDelegation=</varname></term>
 686           <listitem><para>Whether to enable or disable Router Advertisement sending on a link.
 687           Allowed values are <literal>static</literal> which distributes prefixes as defined in
 688           the <literal>[IPv6PrefixDelegation]</literal> and any <literal>[IPv6Prefix]</literal>
 689           sections, <literal>dhcpv6</literal> which requests prefixes using a DHCPv6 client
 690           configured for another link and any values configured in the
 691           <literal>[IPv6PrefixDelegation]</literal> section while ignoring all static prefix
 692           configuration sections, <literal>yes</literal> which uses both static configuration
 693           and DHCPv6, and <literal>false</literal> which turns off IPv6 prefix delegation
 694           altogether. Defaults to <literal>false</literal>. See the
 695           <literal>[IPv6PrefixDelegation]</literal> and the <literal>[IPv6Prefix]</literal>
 696           sections for more configuration options.
 697           </para></listitem>
 698         </varlistentry>
 699         <varlistentry>
 700           <term><varname>IPv6MTUBytes=</varname></term>
 701           <listitem><para>Configures IPv6 maximum transmission unit (MTU).
 702           An integer greater than or equal to 1280 bytes. When unset, the kernel's default will be used.
 703           </para></listitem>
 704         </varlistentry>
 705         <varlistentry>
 706           <term><varname>Bridge=</varname></term>
 707           <listitem>
 708             <para>The name of the bridge to add the link to. See
 709             <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 710             </para>
 711           </listitem>
 712         </varlistentry>
 713         <varlistentry>
 714           <term><varname>Bond=</varname></term>
 715           <listitem>
 716             <para>The name of the bond to add the link to. See
 717             <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 718             </para>
 719           </listitem>
 720         </varlistentry>
 721         <varlistentry>
 722           <term><varname>VRF=</varname></term>
 723           <listitem>
 724             <para>The name of the VRF to add the link to. See
 725             <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 726             </para>
 727           </listitem>
 728         </varlistentry>
 729         <varlistentry>
 730           <term><varname>VLAN=</varname></term>
 731           <listitem>
 732             <para>The name of a VLAN to create on the link. See
 733             <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 734             This option may be specified more than once.</para>
 735           </listitem>
 736         </varlistentry>
 737         <varlistentry>
 738           <term><varname>IPVLAN=</varname></term>
 739           <listitem>
 740             <para>The name of a IPVLAN to create on the link. See
 741             <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 742             This option may be specified more than once.</para>
 743           </listitem>
 744         </varlistentry>
 745         <varlistentry>
 746           <term><varname>MACVLAN=</varname></term>
 747           <listitem>
 748             <para>The name of a MACVLAN to create on the link. See
 749             <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 750             This option may be specified more than once.</para>
 751           </listitem>
 752         </varlistentry>
 753         <varlistentry>
 754           <term><varname>VXLAN=</varname></term>
 755           <listitem>
 756             <para>The name of a VXLAN to create on the link. See
 757             <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 758             This option may be specified more than once.</para>
 759           </listitem>
 760         </varlistentry>
 761         <varlistentry>
 762           <term><varname>Tunnel=</varname></term>
 763           <listitem>
 764             <para>The name of a Tunnel to create on the link. See
 765             <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 766             This option may be specified more than once.</para>
 767           </listitem>
 768         </varlistentry>
 769       <varlistentry>
 770         <term><varname>ActiveSlave=</varname></term>
 771         <listitem>
 772           <para>Takes a boolean. Specifies the new active slave. The <literal>ActiveSlave=</literal>
 773           option is only valid for following modes:
 774           <literal>active-backup</literal>,
 775           <literal>balance-alb</literal> and
 776           <literal>balance-tlb</literal>. Defaults to false.
 777           </para>
 778         </listitem>
 779       </varlistentry>
 780       <varlistentry>
 781         <term><varname>PrimarySlave=</varname></term>
 782         <listitem>
 783           <para>Takes a boolean. Specifies which slave is the primary device. The specified
 784           device will always be the active slave while it is available. Only when the
 785           primary is off-line will alternate devices be used.  This is useful when
 786           one slave is preferred over another, e.g. when one slave has higher throughput
 787           than another. The <literal>PrimarySlave=</literal> option is only valid for
 788           following modes:
 789           <literal>active-backup</literal>,
 790           <literal>balance-alb</literal> and
 791           <literal>balance-tlb</literal>. Defaults to false.
 792           </para>
 793         </listitem>
 794       </varlistentry>
 795       <varlistentry>
 796         <term><varname>ConfigureWithoutCarrier=</varname></term>
 797         <listitem>
 798           <para>Takes a boolean. Allows networkd to configure a specific link even if it has no carrier.
 799           Defaults to false.
 800           </para>
 801         </listitem>
 802       </varlistentry>
 803       <varlistentry>
 804         <term><varname>IgnoreCarrierLoss=</varname></term>
 805         <listitem>
 806           <para>A boolean. Allows networkd to retain both the static and dynamic configuration of the
 807           interface even if its carrier is lost. Defaults to false.
 808           </para>
 809         </listitem>
 810       </varlistentry>
 811
 812       </variablelist>
 813
 814   </refsect1>
 815
 816   <refsect1>
 817     <title>[Address] Section Options</title>
 818
 819       <para>An <literal>[Address]</literal> section accepts the
 820       following keys. Specify several <literal>[Address]</literal>
 821       sections to configure several addresses.</para>
 822
 823       <variablelist class='network-directives'>
 824         <varlistentry>
 825           <term><varname>Address=</varname></term>
 826           <listitem>
 827             <para>As in the <literal>[Network]</literal> section. This key is mandatory. Each
 828             <literal>[Address]</literal> section can contain one <varname>Address=</varname> setting.</para>
 829           </listitem>
 830         </varlistentry>
 831         <varlistentry>
 832           <term><varname>Peer=</varname></term>
 833           <listitem>
 834             <para>The peer address in a point-to-point connection.
 835             Accepts the same format as the <varname>Address=</varname>
 836             key.</para>
 837           </listitem>
 838         </varlistentry>
 839         <varlistentry>
 840           <term><varname>Broadcast=</varname></term>
 841           <listitem>
 842             <para>The broadcast address, which must be in the format
 843             described in
 844             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 845             This key only applies to IPv4 addresses. If it is not
 846             given, it is derived from the <varname>Address=</varname>
 847             key.</para>
 848           </listitem>
 849         </varlistentry>
 850         <varlistentry>
 851           <term><varname>Label=</varname></term>
 852           <listitem>
 853             <para>An address label.</para>
 854           </listitem>
 855         </varlistentry>
 856         <varlistentry>
 857           <term><varname>PreferredLifetime=</varname></term>
 858           <listitem>
 859             <para>Allows the default "preferred lifetime" of the address to be overridden.
 860             Only three settings are accepted: <literal>forever</literal> or <literal>infinity</literal>
 861             which is the default and means that the address never expires, and <literal>0</literal> which means
 862             that the address is considered immediately "expired" and will not be used,
 863             unless explicitly requested. A setting of PreferredLifetime=0 is useful for
 864             addresses which are added to be used only by a specific application,
 865             which is then configured to use them explicitly.</para>
 866           </listitem>
 867         </varlistentry>
 868         <varlistentry>
 869           <term><varname>Scope=</varname></term>
 870           <listitem>
 871             <para>The scope of the address, which can be <literal>global</literal>,
 872             <literal>link</literal> or <literal>host</literal> or an unsigned integer ranges 0 to 255.
 873             Defaults to <literal>global</literal>.</para>
 874           </listitem>
 875         </varlistentry>
 876         <varlistentry>
 877           <term><varname>HomeAddress=</varname></term>
 878           <listitem>
 879             <para>Takes a boolean. Designates this address the "home address" as defined in
 880             <ulink url="https://tools.ietf.org/html/rfc6275">RFC 6275</ulink>.
 881             Supported only on IPv6. Defaults to false.</para>
 882           </listitem>
 883         </varlistentry>
 884         <varlistentry>
 885           <term><varname>DuplicateAddressDetection=</varname></term>
 886           <listitem>
 887             <para>Takes a boolean. Do not perform Duplicate Address Detection
 888             <ulink url="https://tools.ietf.org/html/rfc4862">RFC 4862</ulink> when adding this address.
 889             Supported only on IPv6. Defaults to false.</para>
 890           </listitem>
 891         </varlistentry>
 892         <varlistentry>
 893           <term><varname>ManageTemporaryAddress=</varname></term>
 894           <listitem>
 895             <para>Takes a boolean. If true the kernel manage temporary addresses created
 896             from this one as template on behalf of Privacy Extensions
 897             <ulink url="https://tools.ietf.org/html/rfc3041">RFC 3041</ulink>.  For this to become
 898             active, the use_tempaddr sysctl setting has to be set to a value greater than zero.
 899             The given address needs to have a prefix length of 64. This flag allows to use privacy
 900             extensions in a manually configured network, just like if stateless auto-configuration
 901             was active. Defaults to false. </para>
 902           </listitem>
 903         </varlistentry>
 904         <varlistentry>
 905           <term><varname>PrefixRoute=</varname></term>
 906           <listitem>
 907             <para>Takes a boolean. When adding or modifying an IPv6 address, the userspace
 908             application needs a way to suppress adding a prefix route. This is for example relevant
 909             together with IFA_F_MANAGERTEMPADDR, where userspace creates autoconf generated addresses,
 910             but depending on on-link, no route for the prefix should be added. Defaults to false.</para>
 911           </listitem>
 912         </varlistentry>
 913         <varlistentry>
 914           <term><varname>AutoJoin=</varname></term>
 915           <listitem>
 916             <para>Takes a boolean. Joining multicast group on ethernet level via
 917             <command>ip maddr</command> command would not work if we have an Ethernet switch that does
 918             IGMP snooping since the switch would not replicate multicast packets on  ports that did not
 919             have IGMP reports for the multicast addresses. Linux vxlan interfaces created via
 920             <command>ip link add vxlan</command> or networkd's netdev kind vxlan have the group option
 921             that enables then to do the required join. By extending ip address command with option
 922             <literal>autojoin</literal> we can get similar functionality for openvswitch (OVS) vxlan
 923             interfaces as well as other tunneling mechanisms that need to receive multicast traffic.
 924             Defaults to <literal>no</literal>.</para>
 925           </listitem>
 926         </varlistentry>
 927       </variablelist>
 928   </refsect1>
 929
 930   <refsect1>
 931     <title>[Neighbor] Section Options</title>
 932       <para>A <literal>[Neighbor]</literal> section accepts the
 933       following keys. The neighbor section adds a permanent, static
 934       entry to the neighbor table (IPv6) or ARP table (IPv4) for
 935       the given hardware address on the links matched for the network.
 936       Specify several <literal>[Neighbor]</literal> sections to configure
 937       several static neighbors.</para>
 938
 939       <variablelist class='network-directives'>
 940         <varlistentry>
 941           <term><varname>Address=</varname></term>
 942           <listitem>
 943             <para>The IP address of the neighbor.</para>
 944           </listitem>
 945         </varlistentry>
 946         <varlistentry>
 947           <term><varname>MACAddress=</varname></term>
 948           <listitem>
 949             <para>The hardware address of the neighbor.</para>
 950           </listitem>
 951         </varlistentry>
 952       </variablelist>
 953   </refsect1>
 954
 955     <refsect1>
 956     <title>[IPv6AddressLabel] Section Options</title>
 957
 958       <para>An <literal>[IPv6AddressLabel]</literal> section accepts the
 959       following keys. Specify several <literal>[IPv6AddressLabel]</literal>
 960       sections to configure several address labels. IPv6 address labels are
 961       used for address selection. See <ulink url="https://tools.ietf.org/html/rfc3484">RFC 3484</ulink>.
 962       Precedence is managed by userspace, and only the label itself is stored in the kernel</para>
 963
 964       <variablelist class='network-directives'>
 965         <varlistentry>
 966           <term><varname>Label=</varname></term>
 967           <listitem>
 968             <para> The label for the prefix (an unsigned integer) ranges 0 to 4294967294.
 969             0xffffffff is reserved. This key is mandatory.</para>
 970           </listitem>
 971         </varlistentry>
 972         <varlistentry>
 973           <term><varname>Prefix=</varname></term>
 974           <listitem>
 975             <para>IPv6 prefix is an address with a prefix length, separated by a slash <literal>/</literal> character.
 976             This key is mandatory. </para>
 977           </listitem>
 978         </varlistentry>
 979       </variablelist>
 980   </refsect1>
 981
 982  <refsect1>
 983     <title>[RoutingPolicyRule] Section Options</title>
 984
 985       <para>An <literal>[RoutingPolicyRule]</literal> section accepts the
 986       following keys. Specify several <literal>[RoutingPolicyRule]</literal>
 987       sections to configure several rules.</para>
 988
 989       <variablelist class='network-directives'>
 990         <varlistentry>
 991           <term><varname>TypeOfService=</varname></term>
 992           <listitem>
 993             <para>Specifies the type of service to match a number between 0 to 255.</para>
 994           </listitem>
 995         </varlistentry>
 996         <varlistentry>
 997           <term><varname>From=</varname></term>
 998           <listitem>
 999             <para>Specifies the source address prefix to match. Possibly followed by a slash and the prefix length.</para>
1000           </listitem>
1001         </varlistentry>
1002         <varlistentry>
1003           <term><varname>To=</varname></term>
1004           <listitem>
1005             <para>Specifies the destination address prefix to match. Possibly followed by a slash and the prefix length.</para>
1006           </listitem>
1007         </varlistentry>
1008         <varlistentry>
1009           <term><varname>FirewallMark=</varname></term>
1010           <listitem>
1011             <para>Specifies the iptables firewall mark value to match (a number between 1 and 4294967295).</para>
1012           </listitem>
1013         </varlistentry>
1014         <varlistentry>
1015           <term><varname>Table=</varname></term>
1016           <listitem>
1017             <para>Specifies the routing table identifier to lookup if the rule
1018             selector matches. The table identifier for a route (a number between 1 and 4294967295).</para>
1019           </listitem>
1020         </varlistentry>
1021         <varlistentry>
1022           <term><varname>Priority=</varname></term>
1023           <listitem>
1024             <para>Specifies the priority of this rule. <varname>Priority=</varname> is an unsigned
1025             integer. Higher number means lower priority, and rules get processed in order of increasing number.</para>
1026           </listitem>
1027         </varlistentry>
1028         <varlistentry>
1029           <term><varname>IncomingInterface=</varname></term>
1030           <listitem>
1031             <para>Specifies incoming device to match. If the interface is loopback, the rule only matches packets originating from this host.</para>
1032           </listitem>
1033         </varlistentry>
1034         <varlistentry>
1035           <term><varname>OutgoingInterface=</varname></term>
1036           <listitem>
1037             <para>Specifies the outgoing device to match. The outgoing interface is only available for packets originating from local sockets that are bound to a device.</para>
1038           </listitem>
1039         </varlistentry>
1040         <varlistentry>
1041           <term><varname>SourcePort=</varname></term>
1042           <listitem>
1043             <para>Specifies the source IP port or IP port range match in forwarding information base (FIB) rules.
1044             A port range is specified by the lower and upper port separated by a dash. Defaults to unset.</para>
1045           </listitem>
1046         </varlistentry>
1047         <varlistentry>
1048           <term><varname>DestinationPort=</varname></term>
1049           <listitem>
1050             <para>Specifies the destination IP port or IP port range match in forwarding information base (FIB) rules.
1051             A port range is specified by the lower and upper port separated by a dash. Defaults to unset.</para>
1052           </listitem>
1053         </varlistentry>
1054         <varlistentry>
1055           <term><varname>IPProtocol=</varname></term>
1056           <listitem>
1057             <para>Specifies the IP protocol to match in forwarding information base (FIB) rules. Takes IP protocol name such as <literal>tcp</literal>,
1058             <literal>udp</literal> or <literal>sctp</literal>, or IP protocol number such as <literal>6</literal> for <literal>tcp</literal> or
1059             <literal>17</literal> for <literal>udp</literal>.
1060             Defaults to unset.</para>
1061           </listitem>
1062         </varlistentry>
1063         <varlistentry>
1064           <term><varname>InvertRule=</varname></term>
1065           <listitem>
1066             <para>A boolean. Specifies wheather the rule to be inverted. Defaults to false.</para>
1067           </listitem>
1068         </varlistentry>
1069       </variablelist>
1070   </refsect1>
1071
1072   <refsect1>
1073     <title>[Route] Section Options</title>
1074       <para>The <literal>[Route]</literal> section accepts the
1075       following keys. Specify several <literal>[Route]</literal>
1076       sections to configure several routes.</para>
1077
1078       <variablelist class='network-directives'>
1079         <varlistentry>
1080           <term><varname>Gateway=</varname></term>
1081           <listitem>
1082             <para>As in the <literal>[Network]</literal> section.</para>
1083           </listitem>
1084         </varlistentry>
1085          <varlistentry>
1086            <term><varname>GatewayOnLink=</varname></term>
1087            <listitem>
1088              <para>Takes a boolean. If set to true, the kernel does not have
1089              to check if the gateway is reachable directly by the current machine (i.e., the kernel does
1090              not need to check if the gateway is attached to the local network), so that we can insert the
1091              route in the kernel table without it being complained about. Defaults to <literal>no</literal>.
1092              </para>
1093            </listitem>
1094          </varlistentry>
1095         <varlistentry>
1096           <term><varname>Destination=</varname></term>
1097           <listitem>
1098             <para>The destination prefix of the route. Possibly
1099             followed by a slash and the prefix length. If omitted, a
1100             full-length host route is assumed.</para>
1101           </listitem>
1102         </varlistentry>
1103         <varlistentry>
1104           <term><varname>Source=</varname></term>
1105           <listitem>
1106             <para>The source prefix of the route. Possibly followed by
1107             a slash and the prefix length. If omitted, a full-length
1108             host route is assumed.</para>
1109           </listitem>
1110         </varlistentry>
1111         <varlistentry>
1112           <term><varname>Metric=</varname></term>
1113           <listitem>
1114             <para>The metric of the route (an unsigned integer).</para>
1115           </listitem>
1116         </varlistentry>
1117         <varlistentry>
1118           <term><varname>IPv6Preference=</varname></term>
1119           <listitem>
1120             <para>Specifies the route preference as defined in <ulink
1121             url="https://tools.ietf.org/html/rfc4191">RFC4191</ulink> for Router Discovery messages.
1122             Which can be one of <literal>low</literal> the route has a lowest priority,
1123             <literal>medium</literal> the route has a default priority or
1124             <literal>high</literal> the route has a highest priority.</para>
1125           </listitem>
1126         </varlistentry>
1127         <varlistentry>
1128           <term><varname>Scope=</varname></term>
1129           <listitem>
1130             <para>The scope of the route, which can be <literal>global</literal>,
1131             <literal>link</literal> or <literal>host</literal>. Defaults to
1132             <literal>global</literal>.</para>
1133           </listitem>
1134         </varlistentry>
1135         <varlistentry>
1136           <term><varname>PreferredSource=</varname></term>
1137           <listitem>
1138             <para>The preferred source address of the route. The address
1139             must be in the format described in
1140             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
1141           </listitem>
1142         </varlistentry>
1143         <varlistentry>
1144           <term><varname>Table=<replaceable>num</replaceable></varname></term>
1145           <listitem>
1146           <para>The table identifier for the route (a number between 1 and 4294967295, or 0 to unset).
1147           The table can be retrieved using <command>ip route show table <replaceable>num</replaceable></command>.
1148           </para>
1149           </listitem>
1150         </varlistentry>
1151         <varlistentry>
1152           <term><varname>Protocol=</varname></term>
1153           <listitem>
1154             <para>The protocol identifier for the route. Takes a number between 0 and 255 or the special values
1155             <literal>kernel</literal>, <literal>boot</literal> and <literal>static</literal>. Defaults to
1156             <literal>static</literal>.
1157             </para>
1158           </listitem>
1159         </varlistentry>
1160         <varlistentry>
1161           <term><varname>Type=</varname></term>
1162           <listitem>
1163             <para>Specifies the type for the route. If <literal>unicast</literal>, a regular route is defined, i.e. a
1164             route indicating the path to take to a destination network address. If <literal>blackhole</literal>, packets
1165             to the defined route are discarded silently. If <literal>unreachable</literal>, packets to the defined route
1166             are discarded and the ICMP message "Host Unreachable" is generated. If <literal>prohibit</literal>, packets
1167             to the defined route are discarded and the ICMP message "Communication Administratively Prohibited" is
1168             generated. If <literal>throw</literal>, route lookup in the current routing table will fail and the route
1169             selection process will return to Routing Policy Database (RPDB). Defaults to <literal>unicast</literal>.
1170             </para>
1171           </listitem>
1172         </varlistentry>
1173         <varlistentry>
1174           <term><varname>InitialCongestionWindow=</varname></term>
1175           <listitem>
1176             <para>The TCP initial congestion window is used during the start of a TCP connection. During the start of a TCP
1177             session, when a client requests a resource, the server's initial congestion window determines how many data bytes
1178             will be sent during the initial burst of data. Takes a size in bytes between 1 and 4294967295 (2^32 - 1). The usual
1179             suffixes K, M, G are supported and are understood to the base of 1024. When unset, the kernel's default will be used.
1180             </para>
1181           </listitem>
1182         </varlistentry>
1183         <varlistentry>
1184           <term><varname>InitialAdvertisedReceiveWindow=</varname></term>
1185           <listitem>
1186             <para>The TCP initial advertised receive window is the amount of receive data (in bytes) that can initally be buffered at one time
1187             on a connection. The sending host can send only that amount of data before waiting for an acknowledgment and window update
1188             from the receiving host. Takes a size in bytes between 1 and 4294967295 (2^32 - 1). The usual suffixes K, M, G are supported
1189             and are understood to the base of 1024. When unset, the kernel's default will be used.
1190             </para>
1191           </listitem>
1192         </varlistentry>
1193         <varlistentry>
1194           <term><varname>QuickAck=</varname></term>
1195           <listitem>
1196             <para>Takes a boolean. When true enables TCP quick ack mode for the route. When unset, the kernel's default will be used.
1197             </para>
1198           </listitem>
1199         </varlistentry>
1200         <varlistentry>
1201         <term><varname>MTUBytes=</varname></term>
1202         <listitem>
1203           <para>The maximum transmission unit in bytes to set for the
1204           route. The usual suffixes K, M, G, are supported and are
1205           understood to the base of 1024.</para>
1206           <para>Note that if IPv6 is enabled on the interface, and the MTU is chosen
1207           below 1280 (the minimum MTU for IPv6) it will automatically be increased to this value.</para>
1208         </listitem>
1209       </varlistentry>
1210       </variablelist>
1211   </refsect1>
1212
1213   <refsect1>
1214     <title>[DHCP] Section Options</title>
1215       <para>The <literal>[DHCP]</literal> section configures the
1216       DHCPv4 and DHCP6 client, if it is enabled with the
1217       <varname>DHCP=</varname> setting described above:</para>
1218
1219       <variablelist class='network-directives'>
1220         <varlistentry>
1221           <term><varname>UseDNS=</varname></term>
1222           <listitem>
1223             <para>When true (the default), the DNS servers received
1224             from the DHCP server will be used and take precedence over
1225             any statically configured ones.</para>
1226
1227             <para>This corresponds to the <option>nameserver</option>
1228             option in <citerefentry
1229             project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
1230           </listitem>
1231         </varlistentry>
1232         <varlistentry>
1233           <term><varname>UseNTP=</varname></term>
1234           <listitem>
1235             <para>When true (the default), the NTP servers received
1236             from the DHCP server will be used by systemd-timesyncd
1237             and take precedence over any statically configured ones.</para>
1238           </listitem>
1239         </varlistentry>
1240         <varlistentry>
1241           <term><varname>UseMTU=</varname></term>
1242           <listitem>
1243             <para>When true, the interface maximum transmission unit
1244             from the DHCP server will be used on the current link.
1245             If <varname>MTUBytes=</varname> is set, then this setting is ignored.
1246             Defaults to false.</para>
1247           </listitem>
1248         </varlistentry>
1249         <varlistentry>
1250           <term><varname>Anonymize=</varname></term>
1251           <listitem>
1252             <para>Takes a boolean. When true, the options sent to the DHCP server will
1253             follow the <ulink url="https://tools.ietf.org/html/rfc7844">RFC 7844</ulink>
1254             (Anonymity Profiles for DHCP Clients) to minimize disclosure of identifying information.
1255             Defaults to false.</para>
1256
1257             <para>This option should only be set to true when
1258             <varname>MACAddressPolicy=</varname> is set to <literal>random</literal>
1259             (see <citerefentry
1260             project='man-pages'><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para>
1261
1262             <para>Note that this configuration will overwrite others.
1263             In concrete, the following variables will be ignored:
1264             <varname>SendHostname=</varname>, <varname>ClientIdentifier=</varname>,
1265             <varname>UseRoutes=</varname>, <varname>SendHostname=</varname>,
1266             <varname>UseMTU=</varname>, <varname>VendorClassIdentifier=</varname>,
1267             <varname>UseTimezone=</varname>.</para>
1268
1269             <para>With this option enabled DHCP requests will mimic those generated by Microsoft Windows, in
1270             order to reduce the ability to fingerprint and recognize installations. This means DHCP request
1271             sizes will grow and lease data will be more comprehensive than normally, though most of the
1272             requested data is not actually used.</para>
1273           </listitem>
1274         </varlistentry>
1275         <varlistentry>
1276           <term><varname>SendHostname=</varname></term>
1277           <listitem>
1278             <para>When true (the default), the machine's hostname will be sent to the DHCP server.
1279             Note that the machine's hostname must consist only of 7-bit ASCII lower-case characters and
1280             no spaces or dots, and be formatted as a valid DNS domain name. Otherwise, the hostname is not
1281             sent even if this is set to true.</para>
1282           </listitem>
1283         </varlistentry>
1284         <varlistentry>
1285           <term><varname>UseHostname=</varname></term>
1286           <listitem>
1287             <para>When true (the default), the hostname received from
1288             the DHCP server will be set as the transient hostname of the system.
1289             </para>
1290           </listitem>
1291         </varlistentry>
1292         <varlistentry>
1293           <term><varname>Hostname=</varname></term>
1294           <listitem>
1295             <para>Use this value for the hostname which is sent to the DHCP server, instead of machine's hostname.
1296             Note that the specified hostname must consist only of 7-bit ASCII lower-case characters and
1297             no spaces or dots, and be formatted as a valid DNS domain name.</para>
1298           </listitem>
1299         </varlistentry>
1300         <varlistentry>
1301           <term><varname>UseDomains=</varname></term>
1302           <listitem>
1303             <para>Takes a boolean, or the special value <literal>route</literal>. When true, the domain name
1304             received from the DHCP server will be used as DNS search domain over this link, similar to the effect of
1305             the <option>Domains=</option> setting. If set to <literal>route</literal>, the domain name received from
1306             the DHCP server will be used for routing DNS queries only, but not for searching, similar to the effect of
1307             the <option>Domains=</option> setting when the argument is prefixed with <literal>~</literal>. Defaults to
1308             false.</para>
1309
1310             <para>It is recommended to enable this option only on trusted networks, as setting this affects resolution
1311             of all host names, in particular of single-label names. It is generally safer to use the supplied domain
1312             only as routing domain, rather than as search domain, in order to not have it affect local resolution of
1313             single-label names.</para>
1314
1315             <para>When set to true, this setting corresponds to the <option>domain</option> option in <citerefentry
1316             project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
1317           </listitem>
1318         </varlistentry>
1319         <varlistentry>
1320           <term><varname>UseRoutes=</varname></term>
1321           <listitem>
1322             <para>When true (the default), the static routes will be requested from the DHCP server and added to the
1323               routing table with a metric of 1024, and a scope of "global", "link" or "host", depending on the route's
1324               destination and gateway. If the destination is on the local host, e.g., 127.x.x.x, or the same as the
1325               link's own address, the scope will be set to "host". Otherwise if the gateway is null (a direct route), a
1326               "link" scope will be used. For anything else, scope defaults to "global".</para>
1327           </listitem>
1328         </varlistentry>
1329
1330         <varlistentry>
1331           <term><varname>UseTimezone=</varname></term>
1332
1333           <listitem><para>When true, the timezone received from the
1334           DHCP server will be set as timezone of the local
1335           system. Defaults to <literal>no</literal>.</para></listitem>
1336         </varlistentry>
1337
1338         <varlistentry>
1339           <term><varname>CriticalConnection=</varname></term>
1340           <listitem>
1341             <para>When true, the connection will never be torn down
1342             even if the DHCP lease expires. This is contrary to the
1343             DHCP specification, but may be the best choice if, say,
1344             the root filesystem relies on this connection. Defaults to
1345             false.</para>
1346           </listitem>
1347         </varlistentry>
1348
1349         <varlistentry>
1350           <term><varname>ClientIdentifier=</varname></term>
1351           <listitem>
1352             <para>The DHCPv4 client identifier to use. Takes one of <literal>mac</literal>, <literal>duid</literal> or <literal>duid-only</literal>.
1353             If set to <literal>mac</literal>, the MAC address of the link is used.
1354             If set to <literal>duid</literal>, an RFC4361-compliant Client ID, which is the combination of IAID and DUID (see below), is used.
1355             If set to <literal>duid-only</literal>, only DUID is used, this may not be RFC compliant, but some setups may require to use this.
1356             Defaults to <literal>duid</literal>.</para>
1357           </listitem>
1358         </varlistentry>
1359
1360         <varlistentry>
1361           <term><varname>VendorClassIdentifier=</varname></term>
1362           <listitem>
1363             <para>The vendor class identifier used to identify vendor
1364             type and configuration.</para>
1365           </listitem>
1366         </varlistentry>
1367
1368         <varlistentry>
1369           <term><varname>UserClass=</varname></term>
1370           <listitem>
1371             <para>A DHCPv4 client can use UserClass option to identify the type or category of user or applications
1372             it represents. The information contained in this option is a string that represents the user class of which
1373             the client is a member. Each class sets an identifying string of information to be used by the DHCP
1374             service to classify clients. Takes a whitespace-separated list of strings.</para>
1375           </listitem>
1376         </varlistentry>
1377
1378         <varlistentry>
1379           <term><varname>DUIDType=</varname></term>
1380           <listitem>
1381             <para>Override the global <varname>DUIDType</varname> setting for this network. See
1382             <citerefentry><refentrytitle>networkd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1383             for a description of possible values.</para>
1384           </listitem>
1385         </varlistentry>
1386
1387         <varlistentry>
1388           <term><varname>DUIDRawData=</varname></term>
1389           <listitem>
1390             <para>Override the global <varname>DUIDRawData</varname> setting for this network. See
1391             <citerefentry><refentrytitle>networkd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1392             for a description of possible values.</para>
1393           </listitem>
1394         </varlistentry>
1395
1396         <varlistentry>
1397           <term><varname>IAID=</varname></term>
1398           <listitem>
1399             <para>The DHCP Identity Association Identifier (IAID) for the interface, a 32-bit unsigned integer.</para>
1400           </listitem>
1401         </varlistentry>
1402
1403         <varlistentry>
1404           <term><varname>RequestBroadcast=</varname></term>
1405           <listitem>
1406             <para>Request the server to use broadcast messages before
1407             the IP address has been configured. This is necessary for
1408             devices that cannot receive RAW packets, or that cannot
1409             receive packets at all before an IP address has been
1410             configured. On the other hand, this must not be enabled on
1411             networks where broadcasts are filtered out.</para>
1412           </listitem>
1413         </varlistentry>
1414
1415         <varlistentry>
1416           <term><varname>RouteMetric=</varname></term>
1417           <listitem>
1418             <para>Set the routing metric for routes specified by the
1419             DHCP server.</para>
1420           </listitem>
1421         </varlistentry>
1422
1423         <varlistentry>
1424           <term><varname>RouteTable=<replaceable>num</replaceable></varname></term>
1425           <listitem>
1426             <para>The table identifier for DHCP routes (a number between 1 and 4294967295, or 0 to unset).
1427             The table can be retrieved using <command>ip route show table <replaceable>num</replaceable></command>.
1428             </para>
1429             <para>When used in combination with <varname>VRF=</varname> the
1430             VRF's routing table is used unless this parameter is specified.
1431             </para>
1432           </listitem>
1433         </varlistentry>
1434
1435         <varlistentry>
1436           <term><varname>ListenPort=</varname></term>
1437           <listitem>
1438             <para>Allow setting custom port for the DHCP client to listen on.</para>
1439           </listitem>
1440         </varlistentry>
1441
1442         <varlistentry>
1443           <term><varname>RapidCommit=</varname></term>
1444           <listitem>
1445             <para>Takes a boolean. The DHCPv6 client can obtain configuration parameters from a DHCPv6 server through
1446             a rapid two-message exchange (solicit and reply). When the rapid commit option is enabled by both
1447             the DHCPv6 client and the DHCPv6 server, the two-message exchange is used, rather than the default
1448             four-method exchange (solicit, advertise, request, and reply). The two-message exchange provides
1449             faster client configuration and is beneficial in environments in which networks are under a heavy load.
1450             See <ulink url="https://tools.ietf.org/html/rfc3315#section-17.2.1">RFC 3315</ulink> for details.
1451             Defaults to true.</para>
1452           </listitem>
1453         </varlistentry>
1454
1455         <varlistentry>
1456           <term><varname>ForceDHCPv6PDOtherInformation=</varname></term>
1457           <listitem>
1458             <para>Takes a boolean that enforces DHCPv6 stateful mode when the 'Other information' bit is set in
1459             Router Advertisement messages. By default setting only the 'O' bit in Router Advertisements
1460             makes DHCPv6 request network information in a stateless manner using a two-message Information
1461             Request and Information Reply message exchange.
1462             <ulink url="https://tools.ietf.org/html/rfc7084">RFC 7084</ulink>, requirement WPD-4, updates
1463             this behavior for a Customer Edge router so that stateful DHCPv6 Prefix Delegation is also
1464             requested when only the 'O' bit is set in Router Advertisements. This option enables such a CE
1465             behavior as it is impossible to automatically distinguish the intention of the 'O' bit otherwise.
1466             By default this option is set to 'false', enable it if no prefixes are delegated when the device
1467             should be acting as a CE router.</para>
1468           </listitem>
1469         </varlistentry>
1470
1471       </variablelist>
1472     </refsect1>
1473
1474   <refsect1>
1475     <title>[IPv6AcceptRA] Section Options</title>
1476       <para>The <literal>[IPv6AcceptRA]</literal> section configures the IPv6 Router Advertisement
1477       (RA) client, if it is enabled with the <varname>IPv6AcceptRA=</varname> setting described
1478       above:</para>
1479
1480       <variablelist class='network-directives'>
1481         <varlistentry>
1482           <term><varname>UseDNS=</varname></term>
1483           <listitem>
1484             <para>When true (the default), the DNS servers received in the Router Advertisement will be used and take
1485             precedence over any statically configured ones.</para>
1486
1487             <para>This corresponds to the <option>nameserver</option> option in <citerefentry
1488             project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
1489           </listitem>
1490         </varlistentry>
1491
1492         <varlistentry>
1493           <term><varname>UseDomains=</varname></term>
1494           <listitem>
1495             <para>Takes a boolean, or the special value <literal>route</literal>. When true, the domain name
1496             received via IPv6 Router Advertisement (RA) will be used as DNS search domain over this link, similar to
1497             the effect of the <option>Domains=</option> setting. If set to <literal>route</literal>, the domain name
1498             received via IPv6 RA will be used for routing DNS queries only, but not for searching, similar to the
1499             effect of the <option>Domains=</option> setting when the argument is prefixed with
1500             <literal>~</literal>. Defaults to false.</para>
1501
1502             <para>It is recommended to enable this option only on trusted networks, as setting this affects resolution
1503             of all host names, in particular of single-label names. It is generally safer to use the supplied domain
1504             only as routing domain, rather than as search domain, in order to not have it affect local resolution of
1505             single-label names.</para>
1506
1507             <para>When set to true, this setting corresponds to the <option>domain</option> option in <citerefentry
1508             project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
1509           </listitem>
1510         </varlistentry>
1511
1512         <varlistentry>
1513           <term><varname>RouteTable=<replaceable>num</replaceable></varname></term>
1514           <listitem>
1515             <para>The table identifier for the routes received in the Router Advertisement
1516             (a number between 1 and 4294967295, or 0 to unset).
1517             The table can be retrieved using <command>ip route show table <replaceable>num</replaceable></command>.
1518             </para>
1519           </listitem>
1520         </varlistentry>
1521
1522         <varlistentry>
1523           <term><varname>UseAutonomousPrefix=</varname></term>
1524           <listitem>
1525             <para>When true (the default), the autonomous prefix received in the Router Advertisement will be used and take
1526             precedence over any statically configured ones.</para>
1527           </listitem>
1528         </varlistentry>
1529
1530         <varlistentry>
1531           <term><varname>UseOnLinkPrefix=</varname></term>
1532           <listitem>
1533             <para>When true (the default), the onlink prefix received in the Router Advertisement will be used and take
1534             precedence over any statically configured ones.</para>
1535           </listitem>
1536         </varlistentry>
1537
1538       </variablelist>
1539   </refsect1>
1540
1541   <refsect1>
1542     <title>[DHCPServer] Section Options</title>
1543     <para>The <literal>[DHCPServer]</literal> section contains
1544     settings for the DHCP server, if enabled via the
1545     <varname>DHCPServer=</varname> option described above:</para>
1546
1547     <variablelist class='network-directives'>
1548
1549       <varlistentry>
1550         <term><varname>PoolOffset=</varname></term>
1551         <term><varname>PoolSize=</varname></term>
1552
1553         <listitem><para>Configures the pool of addresses to hand out. The pool
1554         is a contiguous sequence of IP addresses in the subnet configured for
1555         the server address, which does not include the subnet nor the broadcast
1556         address. <varname>PoolOffset=</varname> takes the offset of the pool
1557         from the start of subnet, or zero to use the default value.
1558         <varname>PoolSize=</varname> takes the number of IP addresses in the
1559         pool or zero to use the default value. By default, the pool starts at
1560         the first address after the subnet address and takes up the rest of
1561         the subnet, excluding the broadcast address. If the pool includes
1562         the server address (the default), this is reserved and not handed
1563         out to clients.</para></listitem>
1564       </varlistentry>
1565
1566       <varlistentry>
1567         <term><varname>DefaultLeaseTimeSec=</varname></term>
1568         <term><varname>MaxLeaseTimeSec=</varname></term>
1569
1570         <listitem><para>Control the default and maximum DHCP lease
1571         time to pass to clients. These settings take time values in seconds or
1572         another common time unit, depending on the suffix. The default
1573         lease time is used for clients that did not ask for a specific
1574         lease time. If a client asks for a lease time longer than the
1575         maximum lease time, it is automatically shortened to the
1576         specified time. The default lease time defaults to 1h, the
1577         maximum lease time to 12h. Shorter lease times are beneficial
1578         if the configuration data in DHCP leases changes frequently
1579         and clients shall learn the new settings with shorter
1580         latencies. Longer lease times reduce the generated DHCP
1581         network traffic.</para></listitem>
1582       </varlistentry>
1583
1584       <varlistentry>
1585         <term><varname>EmitDNS=</varname></term>
1586         <term><varname>DNS=</varname></term>
1587
1588         <listitem><para>Takes a boolean. Configures whether the DHCP leases handed out
1589         to clients shall contain DNS server information. Defaults to <literal>yes</literal>.
1590         The DNS servers to pass to clients may be configured with the
1591         <varname>DNS=</varname> option, which takes a list of IPv4
1592         addresses. If the <varname>EmitDNS=</varname> option is
1593         enabled but no servers configured, the servers are
1594         automatically propagated from an "uplink" interface that has
1595         appropriate servers set. The "uplink" interface is determined
1596         by the default route of the system with the highest
1597         priority. Note that this information is acquired at the time
1598         the lease is handed out, and does not take uplink interfaces
1599         into account that acquire DNS or NTP server information at a
1600         later point. DNS server propagation does not take
1601         <filename>/etc/resolv.conf</filename> into account. Also, note
1602         that the leases are not refreshed if the uplink network
1603         configuration changes. To ensure clients regularly acquire the
1604         most current uplink DNS server information, it is thus
1605         advisable to shorten the DHCP lease time via
1606         <varname>MaxLeaseTimeSec=</varname> described
1607         above.</para></listitem>
1608       </varlistentry>
1609
1610       <varlistentry>
1611         <term><varname>EmitNTP=</varname></term>
1612         <term><varname>NTP=</varname></term>
1613
1614         <listitem><para>Similar to the <varname>EmitDNS=</varname> and
1615         <varname>DNS=</varname> settings described above, these
1616         settings configure whether and what NTP server information
1617         shall be emitted as part of the DHCP lease. The same syntax,
1618         propagation semantics and defaults apply as for
1619         <varname>EmitDNS=</varname> and
1620         <varname>DNS=</varname>.</para></listitem>
1621       </varlistentry>
1622
1623       <varlistentry>
1624         <term><varname>EmitRouter=</varname></term>
1625
1626         <listitem><para>Similar to the <varname>EmitDNS=</varname>
1627         setting described above, this setting configures whether the
1628         DHCP lease should contain the router option. The same syntax,
1629         propagation semantics and defaults apply as for
1630         <varname>EmitDNS=</varname>.</para></listitem>
1631       </varlistentry>
1632
1633       <varlistentry>
1634         <term><varname>EmitTimezone=</varname></term>
1635         <term><varname>Timezone=</varname></term>
1636
1637         <listitem><para>Takes a boolean. Configures whether the DHCP leases handed out
1638         to clients shall contain timezone information. Defaults to <literal>yes</literal>. The
1639         <varname>Timezone=</varname> setting takes a timezone string
1640         (such as <literal>Europe/Berlin</literal> or
1641         <literal>UTC</literal>) to pass to clients. If no explicit
1642         timezone is set, the system timezone of the local host is
1643         propagated, as determined by the
1644         <filename>/etc/localtime</filename> symlink.</para></listitem>
1645       </varlistentry>
1646
1647     </variablelist>
1648   </refsect1>
1649
1650   <refsect1>
1651     <title>[IPv6PrefixDelegation] Section Options</title>
1652     <para>The <literal>[IPv6PrefixDelegation]</literal> section contains
1653     settings for sending IPv6 Router Advertisements and whether to act as
1654     a router, if enabled via the <varname>IPv6PrefixDelegation=</varname>
1655     option described above. IPv6 network prefixes are defined with one or
1656     more <literal>[IPv6Prefix]</literal> sections.</para>
1657
1658     <variablelist class='network-directives'>
1659
1660       <varlistentry>
1661         <term><varname>Managed=</varname></term>
1662         <term><varname>OtherInformation=</varname></term>
1663
1664         <listitem><para>Takes a boolean. Controls whether a DHCPv6 server is used to acquire IPv6
1665         addresses on the network link when <varname>Managed=</varname>
1666         is set to <literal>true</literal> or if only additional network
1667         information can be obtained via DHCPv6 for the network link when
1668         <varname>OtherInformation=</varname> is set to
1669         <literal>true</literal>. Both settings default to
1670         <literal>false</literal>, which means that a DHCPv6 server is not being
1671         used.</para></listitem>
1672       </varlistentry>
1673
1674       <varlistentry>
1675         <term><varname>RouterLifetimeSec=</varname></term>
1676
1677         <listitem><para>Takes a timespan. Configures the IPv6 router lifetime in seconds. If set,
1678         this host also announces itself in Router Advertisements as an IPv6
1679         router for the network link. When unset, the host is not acting as a router.</para>
1680         </listitem>
1681       </varlistentry>
1682
1683       <varlistentry>
1684         <term><varname>RouterPreference=</varname></term>
1685
1686         <listitem><para>Configures IPv6 router preference if
1687         <varname>RouterLifetimeSec=</varname> is non-zero. Valid values are
1688         <literal>high</literal>, <literal>medium</literal> and
1689         <literal>low</literal>, with <literal>normal</literal> and
1690         <literal>default</literal> added as synonyms for
1691         <literal>medium</literal> just to make configuration easier. See
1692         <ulink url="https://tools.ietf.org/html/rfc4191">RFC 4191</ulink>
1693         for details. Defaults to <literal>medium</literal>.</para></listitem>
1694       </varlistentry>
1695
1696       <varlistentry>
1697         <term><varname>EmitDNS=</varname></term>
1698         <term><varname>DNS=</varname></term>
1699
1700         <listitem><para><varname>DNS=</varname> specifies a list of recursive
1701         DNS server IPv6 addresses that distributed via Router Advertisement
1702         messages when <varname>EmitDNS=</varname> is true. If <varname>DNS=
1703         </varname> is empty, DNS servers are read from the
1704         <literal>[Network]</literal> section. If the
1705         <literal>[Network]</literal> section does not contain any DNS servers
1706         either, DNS servers from the uplink with the highest priority default
1707         route are used. When <varname>EmitDNS=</varname> is false, no DNS server
1708         information is sent in Router Advertisement messages.
1709         <varname>EmitDNS=</varname> defaults to true.
1710         </para></listitem>
1711       </varlistentry>
1712
1713       <varlistentry>
1714         <term><varname>EmitDomains=</varname></term>
1715         <term><varname>Domains=</varname></term>
1716
1717         <listitem><para>A list of DNS search domains distributed via Router
1718         Advertisement messages when <varname>EmitDomains=</varname> is true. If
1719         <varname>Domains=</varname> is empty, DNS search domains are read from the
1720         <literal>[Network]</literal> section. If the <literal>[Network]</literal>
1721         section does not contain any DNS search domains either, DNS search
1722         domains from the uplink with the highest priority default route are
1723         used. When <varname>EmitDomains=</varname> is false, no DNS search domain
1724         information is sent in Router Advertisement messages.
1725         <varname>EmitDomains=</varname> defaults to true.
1726         </para></listitem>
1727       </varlistentry>
1728
1729       <varlistentry>
1730         <term><varname>DNSLifetimeSec=</varname></term>
1731
1732         <listitem><para>Lifetime in seconds for the DNS server addresses listed
1733         in <varname>DNS=</varname> and search domains listed in
1734         <varname>Domains=</varname>.</para></listitem>
1735       </varlistentry>
1736
1737     </variablelist>
1738     </refsect1>
1739
1740       <refsect1>
1741     <title>[IPv6Prefix] Section Options</title>
1742     <para>One or more <literal>[IPv6Prefix]</literal> sections contain the IPv6
1743     prefixes that are announced via Router Advertisements. See
1744     <ulink url="https://tools.ietf.org/html/rfc4861">RFC 4861</ulink>
1745     for further details.</para>
1746
1747     <variablelist class='network-directives'>
1748
1749       <varlistentry>
1750         <term><varname>AddressAutoconfiguration=</varname></term>
1751         <term><varname>OnLink=</varname></term>
1752
1753         <listitem><para>Takes a boolean to specify whether IPv6 addresses can be
1754         autoconfigured with this prefix and whether the prefix can be used for
1755         onlink determination. Both settings default to <literal>true</literal>
1756         in order to ease configuration.
1757         </para></listitem>
1758       </varlistentry>
1759
1760       <varlistentry>
1761         <term><varname>Prefix=</varname></term>
1762
1763         <listitem><para>The IPv6 prefix that is to be distributed to hosts.
1764         Similarly to configuring static IPv6 addresses, the setting is
1765         configured as an IPv6 prefix and its prefix length, separated by a
1766         <literal>/</literal> character. Use multiple
1767         <literal>[IPv6Prefix]</literal> sections to configure multiple IPv6
1768         prefixes since prefix lifetimes, address autoconfiguration and onlink
1769         status may differ from one prefix to another.</para></listitem>
1770       </varlistentry>
1771
1772       <varlistentry>
1773         <term><varname>PreferredLifetimeSec=</varname></term>
1774         <term><varname>ValidLifetimeSec=</varname></term>
1775
1776         <listitem><para>Preferred and valid lifetimes for the prefix measured in
1777         seconds. <varname>PreferredLifetimeSec=</varname> defaults to 604800
1778         seconds (one week) and <varname>ValidLifetimeSec=</varname> defaults
1779         to 2592000 seconds (30 days).</para></listitem>
1780       </varlistentry>
1781
1782     </variablelist>
1783     </refsect1>
1784
1785     <refsect1>
1786     <title>[Bridge] Section Options</title>
1787       <para>The <literal>[Bridge]</literal> section accepts the
1788       following keys.</para>
1789       <variablelist class='network-directives'>
1790         <varlistentry>
1791           <term><varname>UnicastFlood=</varname></term>
1792           <listitem>
1793             <para>Takes a boolean. Controls whether the bridge should flood
1794             traffic for which an FDB entry is missing and the destination
1795             is unknown through this port. When unset, the kernel's default will be used.
1796             </para>
1797           </listitem>
1798         </varlistentry>
1799         <varlistentry>
1800           <term><varname>MulticastFlood=</varname></term>
1801           <listitem>
1802             <para>Takes a boolean. Controls whether the bridge should flood
1803             traffic for which an MDB entry is missing and the destination
1804             is unknown through this port. When unset, the kernel's default will be used.
1805             </para>
1806           </listitem>
1807         </varlistentry>
1808         <varlistentry>
1809           <term><varname>MulticastToUnicast=</varname></term>
1810           <listitem>
1811             <para>Takes a boolean. Multicast to unicast works on top of the multicast snooping feature of
1812             the bridge. Which means unicast copies are only delivered to hosts which are interested in it.
1813             When unset, the kernel's default will be used.
1814             </para>
1815           </listitem>
1816         </varlistentry>
1817         <varlistentry>
1818           <term><varname>NeighborSuppression=</varname></term>
1819           <listitem>
1820             <para>Takes a boolean. Configures whether ARP and ND neighbor suppression is enabled for
1821             this port. When unset, the kernel's default will be used.
1822             </para>
1823           </listitem>
1824         </varlistentry>
1825         <varlistentry>
1826           <term><varname>Learning=</varname></term>
1827           <listitem>
1828             <para>Takes a boolean. Configures whether MAC address learning is enabled for
1829             this port. When unset, the kernel's default will be used.
1830             </para>
1831           </listitem>
1832         </varlistentry>
1833         <varlistentry>
1834           <term><varname>HairPin=</varname></term>
1835           <listitem>
1836             <para>Takes a boolean. Configures whether traffic may be sent back
1837             out of the port on which it was received. When this flag is false, and the bridge
1838             will not forward traffic back out of the receiving port.
1839             When unset, the kernel's default will be used.</para>
1840           </listitem>
1841         </varlistentry>
1842         <varlistentry>
1843           <term><varname>UseBPDU=</varname></term>
1844           <listitem>
1845             <para>Takes a boolean. Configures whether STP Bridge Protocol Data Units will be
1846             processed by the bridge port. When unset, the kernel's default will be used.</para>
1847           </listitem>
1848         </varlistentry>
1849         <varlistentry>
1850           <term><varname>FastLeave=</varname></term>
1851           <listitem>
1852             <para>Takes a boolean. This flag allows the bridge to immediately stop multicast
1853             traffic on a port that receives an IGMP Leave message. It is only used with
1854             IGMP snooping if enabled on the bridge. When unset, the kernel's default will be used.</para>
1855           </listitem>
1856         </varlistentry>
1857         <varlistentry>
1858           <term><varname>AllowPortToBeRoot=</varname></term>
1859           <listitem>
1860             <para>Takes a boolean. Configures whether a given port is allowed to
1861             become a root port. Only used when STP is enabled on the bridge.
1862             When unset, the kernel's default will be used.</para>
1863           </listitem>
1864         </varlistentry>
1865         <varlistentry>
1866           <term><varname>Cost=</varname></term>
1867           <listitem>
1868             <para>Sets the "cost" of sending packets of this interface.
1869             Each port in a bridge may have a different speed and the cost
1870             is used to decide which link to use. Faster interfaces
1871             should have lower costs. It is an integer value between 1 and
1872             65535.</para>
1873           </listitem>
1874         </varlistentry>
1875         <varlistentry>
1876           <term><varname>Priority=</varname></term>
1877           <listitem>
1878             <para>Sets the "priority" of sending packets on this interface.
1879             Each port in a bridge may have a different priority which is used
1880             to decide which link to use. Lower value means higher priority.
1881             It is an integer value between 0 to 63. Networkd does not set any
1882             default, meaning the kernel default value of 32 is used.</para>
1883           </listitem>
1884         </varlistentry>
1885       </variablelist>
1886   </refsect1>
1887   <refsect1>
1888     <title>[BridgeFDB] Section Options</title>
1889       <para>The <literal>[BridgeFDB]</literal> section manages the
1890       forwarding database table of a port and accepts the following
1891       keys. Specify several <literal>[BridgeFDB]</literal> sections to
1892       configure several static MAC table entries.</para>
1893
1894       <variablelist class='network-directives'>
1895         <varlistentry>
1896           <term><varname>MACAddress=</varname></term>
1897           <listitem>
1898             <para>As in the <literal>[Network]</literal> section. This
1899             key is mandatory.</para>
1900           </listitem>
1901         </varlistentry>
1902         <varlistentry>
1903           <term><varname>VLANId=</varname></term>
1904           <listitem>
1905             <para>The VLAN ID for the new static MAC table entry. If
1906             omitted, no VLAN ID information is appended to the new static MAC
1907             table entry.</para>
1908           </listitem>
1909         </varlistentry>
1910       </variablelist>
1911   </refsect1>
1912
1913   <refsect1>
1914     <title>[CAN] Section Options</title>
1915       <para>The <literal>[CAN]</literal> section manages the Controller Area Network (CAN bus) and accepts the
1916       following keys.</para>
1917       <variablelist class='network-directives'>
1918         <varlistentry>
1919           <term><varname>BitRate=</varname></term>
1920           <listitem>
1921             <para>The bitrate of CAN device in bits per second. The usual SI prefixes (K, M) with the base of 1000 can
1922             be used here.</para>
1923           </listitem>
1924         </varlistentry>
1925         <varlistentry>
1926           <term><varname>SamplePoint=</varname></term>
1927           <listitem>
1928             <para>Optional sample point in percent with one decimal (e.g. <literal>75%</literal>,
1929             <literal>87.5%</literal>) or permille (e.g. <literal>875‰</literal>).</para>
1930           </listitem>
1931         </varlistentry>
1932         <varlistentry>
1933           <term><varname>RestartSec=</varname></term>
1934           <listitem>
1935             <para>Automatic restart delay time. If set to a non-zero value, a restart of the CAN controller will be
1936             triggered automatically in case of a bus-off condition after the specified delay time. Subsecond delays can
1937             be specified using decimals (e.g. <literal>0.1s</literal>) or a <literal>ms</literal> or
1938             <literal>us</literal> postfix. Using <literal>infinity</literal> or <literal>0</literal> will turn the
1939             automatic restart off. By default automatic restart is disabled.</para>
1940           </listitem>
1941         </varlistentry>
1942         <varlistentry>
1943           <term><varname>TripleSampling=</varname></term>
1944           <listitem>
1945             <para>Takes a boolean. When <literal>yes</literal>, three samples (instead of one) are used to determine
1946             the value of a received bit by majority rule. When unset, the kernel's default will be used.</para>
1947           </listitem>
1948         </varlistentry>
1949       </variablelist>
1950   </refsect1>
1951
1952   <refsect1>
1953     <title>[BridgeVLAN] Section Options</title>
1954       <para>The <literal>[BridgeVLAN]</literal> section manages the VLAN ID configuration of a bridge port and accepts
1955       the following keys. Specify several <literal>[BridgeVLAN]</literal> sections to configure several VLAN entries.
1956       The <varname>VLANFiltering=</varname> option has to be enabled, see <literal>[Bridge]</literal> section in
1957       <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
1958
1959       <variablelist class='network-directives'>
1960         <varlistentry>
1961           <term><varname>VLAN=</varname></term>
1962           <listitem>
1963             <para>The VLAN ID allowed on the port. This can be either a single ID or a range M-N. VLAN IDs are valid
1964             from 1 to 4094.</para>
1965           </listitem>
1966         </varlistentry>
1967         <varlistentry>
1968           <term><varname>EgressUntagged=</varname></term>
1969           <listitem>
1970             <para>The VLAN ID specified here will be used to untag frames on egress. Configuring
1971             <varname>EgressUntagged=</varname> implicates the use of <varname>VLAN=</varname> above and will enable the
1972             VLAN ID for ingress as well. This can be either a single ID or a range M-N.</para>
1973           </listitem>
1974         </varlistentry>
1975         <varlistentry>
1976           <term><varname>PVID=</varname></term>
1977           <listitem>
1978             <para>The Port VLAN ID specified here is assigned to all untagged frames at ingress.
1979             <varname>PVID=</varname> can be used only once. Configuring <varname>PVID=</varname> implicates the use of
1980             <varname>VLAN=</varname> above and will enable the VLAN ID for ingress as well.</para>
1981           </listitem>
1982         </varlistentry>
1983       </variablelist>
1984   </refsect1>
1985
1986   <refsect1>
1987     <title>Examples</title>
1988     <example>
1989       <title>Static network configuration</title>
1990
1991       <programlisting># /etc/systemd/network/50-static.network
1992 [Match]
1993 Name=enp2s0
1994
1995 [Network]
1996 Address=192.168.0.15/24
1997 Gateway=192.168.0.1</programlisting>
1998
1999       <para>This brings interface <literal>enp2s0</literal> up with a static address. The
2000       specified gateway will be used for a default route.</para>
2001     </example>
2002
2003     <example>
2004       <title>DHCP on ethernet links</title>
2005
2006       <programlisting># /etc/systemd/network/80-dhcp.network
2007 [Match]
2008 Name=en*
2009
2010 [Network]
2011 DHCP=yes</programlisting>
2012
2013       <para>This will enable DHCPv4 and DHCPv6 on all interfaces with names starting with
2014       <literal>en</literal> (i.e. ethernet interfaces).</para>
2015     </example>
2016
2017     <example>
2018       <title>A bridge with two enslaved links</title>
2019
2020       <programlisting># /etc/systemd/network/25-bridge-static.network
2021 [Match]
2022 Name=bridge0
2023
2024 [Network]
2025 Address=192.168.0.15/24
2026 Gateway=192.168.0.1
2027 DNS=192.168.0.1</programlisting>
2028
2029       <programlisting># /etc/systemd/network/25-bridge-slave-interface-1.network
2030 [Match]
2031 Name=enp2s0
2032
2033 [Network]
2034 Bridge=bridge0</programlisting>
2035
2036       <programlisting># /etc/systemd/network/25-bridge-slave-interface-2.network
2037 [Match]
2038 Name=wlp3s0
2039
2040 [Network]
2041 Bridge=bridge0</programlisting>
2042
2043       <para>This creates a bridge and attaches devices <literal>enp2s0</literal> and
2044       <literal>wlp3s0</literal> to it. The bridge will have the specified static address
2045       and network assigned, and a default route via the specified gateway will be
2046       added. The specified DNS server will be added to the global list of DNS resolvers.
2047       </para>
2048     </example>
2049
2050     <example>
2051       <title></title>
2052
2053       <programlisting>
2054 # /etc/systemd/network/20-bridge-slave-interface-vlan.network
2055 [Match]
2056 Name=enp2s0
2057
2058 [Network]
2059 Bridge=bridge0
2060
2061 [BridgeVLAN]
2062 VLAN=1-32
2063 PVID=42
2064 EgressUntagged=42
2065
2066 [BridgeVLAN]
2067 VLAN=100-200
2068
2069 [BridgeVLAN]
2070 EgressUntagged=300-400</programlisting>
2071
2072     <para>This overrides the configuration specified in the previous example for the
2073     interface <literal>enp2s0</literal>, and enables VLAN on that bridge port. VLAN IDs
2074     1-32, 42, 100-400 will be allowed. Packets tagged with VLAN IDs 42, 300-400 will be
2075     untagged when they leave on this interface. Untagged packets which arrive on this
2076     interface will be assigned VLAN ID 42.</para>
2077     </example>
2078
2079     <example>
2080       <title>Various tunnels</title>
2081
2082       <programlisting>/etc/systemd/network/25-tunnels.network
2083 [Match]
2084 Name=ens1
2085
2086 [Network]
2087 Tunnel=ipip-tun
2088 Tunnel=sit-tun
2089 Tunnel=gre-tun
2090 Tunnel=vti-tun
2091       </programlisting>
2092
2093       <programlisting>/etc/systemd/network/25-tunnel-ipip.netdev
2094 [NetDev]
2095 Name=ipip-tun
2096 Kind=ipip
2097       </programlisting>
2098
2099       <programlisting>/etc/systemd/network/25-tunnel-sit.netdev
2100 [NetDev]
2101 Name=sit-tun
2102 Kind=sit
2103       </programlisting>
2104
2105       <programlisting>/etc/systemd/network/25-tunnel-gre.netdev
2106 [NetDev]
2107 Name=gre-tun
2108 Kind=gre
2109       </programlisting>
2110
2111       <programlisting>/etc/systemd/network/25-tunnel-vti.netdev
2112 [NetDev]
2113 Name=vti-tun
2114 Kind=vti
2115       </programlisting>
2116
2117       <para>This will bring interface <literal>ens1</literal> up and create an IPIP tunnel,
2118       a SIT tunnel, a GRE tunnel, and a VTI tunnel using it.</para>
2119     </example>
2120
2121     <example>
2122       <title>A bond device</title>
2123
2124       <programlisting># /etc/systemd/network/30-bond1.network
2125 [Match]
2126 Name=bond1
2127
2128 [Network]
2129 DHCP=ipv6
2130 </programlisting>
2131
2132       <programlisting># /etc/systemd/network/30-bond1.netdev
2133 [NetDev]
2134 Name=bond1
2135 Kind=bond
2136 </programlisting>
2137
2138       <programlisting># /etc/systemd/network/30-bond1-dev1.network
2139 [Match]
2140 MACAddress=52:54:00:e9:64:41
2141
2142 [Network]
2143 Bond=bond1
2144 </programlisting>
2145
2146       <programlisting># /etc/systemd/network/30-bond1-dev2.network
2147 [Match]
2148 MACAddress=52:54:00:e9:64:42
2149
2150 [Network]
2151 Bond=bond1
2152 </programlisting>
2153
2154     <para>This will create a bond device <literal>bond1</literal> and enslave the two
2155     devices with MAC addresses 52:54:00:e9:64:41 and 52:54:00:e9:64:42 to it. IPv6 DHCP
2156     will be used to acquire an address.</para>
2157     </example>
2158
2159     <example>
2160       <title>Virtual Routing and Forwarding (VRF)</title>
2161       <para>Add the <literal>bond1</literal> interface to the VRF master interface
2162       <literal>vrf1</literal>. This will redirect routes generated on this interface to be
2163       within the routing table defined during VRF creation. For kernels before 4.8 traffic
2164       won't be redirected towards the VRFs routing table unless specific ip-rules are added.
2165       </para>
2166       <programlisting># /etc/systemd/network/25-vrf.network
2167 [Match]
2168 Name=bond1
2169
2170 [Network]
2171 VRF=vrf1
2172 </programlisting>
2173     </example>
2174
2175     <example>
2176       <title>MacVTap</title>
2177       <para>This brings up a network interface <literal>macvtap-test</literal>
2178       and attaches it to <literal>enp0s25</literal>.</para>
2179       <programlisting># /usr/lib/systemd/network/25-macvtap.network
2180 [Match]
2181 Name=enp0s25
2182
2183 [Network]
2184 MACVTAP=macvtap-test
2185 </programlisting>
2186     </example>
2187   </refsect1>
2188
2189   <refsect1>
2190     <title>See Also</title>
2191     <para>
2192       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
2193       <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
2194       <citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
2195       <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
2196       <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
2197     </para>
2198   </refsect1>
2199
2200 </refentry>