man/systemd.network.xml

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  23
  24 <refentry id="systemd.network" conditional='ENABLE_NETWORKD'>
  25
  26   <refentryinfo>
  27     <title>systemd.network</title>
  28     <productname>systemd</productname>
  29
  30     <authorgroup>
  31       <author>
  32         <contrib>Developer</contrib>
  33         <firstname>Tom</firstname>
  34         <surname>Gundersen</surname>
  35         <email>teg@jklm.no</email>
  36       </author>
  37     </authorgroup>
  38   </refentryinfo>
  39
  40   <refmeta>
  41     <refentrytitle>systemd.network</refentrytitle>
  42     <manvolnum>5</manvolnum>
  43   </refmeta>
  44
  45   <refnamediv>
  46     <refname>systemd.network</refname>
  47     <refpurpose>Network configuration</refpurpose>
  48   </refnamediv>
  49
  50   <refsynopsisdiv>
  51     <para><filename><replaceable>network</replaceable>.network</filename></para>
  52   </refsynopsisdiv>
  53
  54   <refsect1>
  55     <title>Description</title>
  56
  57     <para>Network setup is performed by
  58     <citerefentry><refentrytitle>systemd-networkd</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
  59     </para>
  60
  61     <para>The main network file must have the extension <filename>.network</filename>; other
  62     extensions are ignored. Networks are applied to links whenever the links appear.</para>
  63
  64     <para>The <filename>.network</filename> files are read from the files located in the system
  65     network directory <filename>/usr/lib/systemd/network</filename>, the volatile runtime network
  66     directory <filename>/run/systemd/network</filename> and the local administration network
  67     directory <filename>/etc/systemd/network</filename>. All configuration files are collectively
  68     sorted and processed in lexical order, regardless of the directories in which they live.
  69     However, files with identical filenames replace each other. Files in <filename>/etc</filename>
  70     have the highest priority, files in <filename>/run</filename> take precedence over files with
  71     the same name in <filename>/usr/lib</filename>. This can be used to override a system-supplied
  72     configuration file with a local file if needed. As a special case, an empty file (file size 0)
  73     or symlink with the same name pointing to <filename>/dev/null</filename> disables the
  74     configuration file entirely (it is "masked").</para>
  75
  76     <para>Along with the network file <filename>foo.network</filename>, a "drop-in" directory
  77     <filename>foo.network.d/</filename> may exist. All files with the suffix
  78     <literal>.conf</literal> from this directory will be parsed after the file itself is
  79     parsed. This is useful to alter or add configuration settings, without having to modify the main
  80     configuration file. Each drop-in file must have appropriate section headers.</para>
  81
  82     <para>In addition to <filename>/etc/systemd/network</filename>, drop-in <literal>.d</literal>
  83     directories can be placed in <filename>/usr/lib/systemd/network</filename> or
  84     <filename>/run/systemd/network</filename> directories. Drop-in files in
  85     <filename>/etc</filename> take precedence over those in <filename>/run</filename> which in turn
  86     take precedence over those in <filename>/usr/lib</filename>. Drop-in files under any of these
  87     directories take precedence over the main netdev file wherever located. (Of course, since
  88     <filename>/run</filename> is temporary and <filename>/usr/lib</filename> is for vendors, it is
  89     unlikely drop-ins should be used in either of those places.)</para>
  90
  91     <para>Note that an interface without any static IPv6 addresses configured, and neither DHCPv6
  92     nor IPv6LL enabled, shall be considered to have no IPv6 support. IPv6 will be automatically
  93     disabled for that interface by writing "1" to
  94     <filename>/proc/sys/net/ipv6/conf/<replaceable>ifname</replaceable>/disable_ipv6</filename>.
  95     </para>
  96   </refsect1>
  97
  98   <refsect1>
  99     <title>[Match] Section Options</title>
 100
 101       <para>The network file contains a <literal>[Match]</literal>
 102       section, which determines if a given network file may be applied
 103       to a given device; and a <literal>[Network]</literal> section
 104       specifying how the device should be configured. The first (in
 105       lexical order) of the network files that matches a given device
 106       is applied, all later files are ignored, even if they match as
 107       well.</para>
 108
 109       <para>A network file is said to match a device if each of the
 110       entries in the <literal>[Match]</literal> section matches, or if
 111       the section is empty. The following keys are accepted:</para>
 112
 113       <variablelist class='network-directives'>
 114         <varlistentry>
 115           <term><varname>MACAddress=</varname></term>
 116           <listitem>
 117             <para>The hardware address of the interface (use full colon-delimited hexadecimal, e.g.,
 118             01:23:45:67:89:ab).</para>
 119           </listitem>
 120         </varlistentry>
 121         <varlistentry>
 122           <term><varname>Path=</varname></term>
 123           <listitem>
 124             <para>A whitespace-separated list of shell-style globs
 125             matching the persistent path, as exposed by the udev
 126             property <literal>ID_PATH</literal>. If the list is
 127             prefixed with a "!", the test is inverted; i.e. it is
 128             true when <literal>ID_PATH</literal> does not match any
 129             item in the list.</para>
 130           </listitem>
 131         </varlistentry>
 132         <varlistentry>
 133           <term><varname>Driver=</varname></term>
 134           <listitem>
 135             <para>A whitespace-separated list of shell-style globs
 136             matching the driver currently bound to the device, as
 137             exposed by the udev property <literal>DRIVER</literal>
 138             of its parent device, or if that is not set the driver
 139             as exposed by <literal>ethtool -i</literal> of the
 140             device itself. If the list is prefixed with a "!", the
 141             test is inverted.</para>
 142           </listitem>
 143         </varlistentry>
 144         <varlistentry>
 145           <term><varname>Type=</varname></term>
 146           <listitem>
 147             <para>A whitespace-separated list of shell-style globs
 148             matching the device type, as exposed by the udev property
 149             <literal>DEVTYPE</literal>. If the list is prefixed with
 150             a "!", the test is inverted.</para>
 151           </listitem>
 152         </varlistentry>
 153         <varlistentry>
 154           <term><varname>Name=</varname></term>
 155           <listitem>
 156             <para>A whitespace-separated list of shell-style globs
 157             matching the device name, as exposed by the udev property
 158             <literal>INTERFACE</literal>. If the list is prefixed
 159             with a "!", the test is inverted.</para>
 160           </listitem>
 161         </varlistentry>
 162         <varlistentry>
 163           <term><varname>Host=</varname></term>
 164           <listitem>
 165             <para>Matches against the hostname or machine ID of the
 166             host. See <literal>ConditionHost=</literal> in
 167             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 168             for details.
 169             </para>
 170           </listitem>
 171         </varlistentry>
 172         <varlistentry>
 173           <term><varname>Virtualization=</varname></term>
 174           <listitem>
 175             <para>Checks whether the system is executed in a virtualized
 176             environment and optionally test whether it is a specific
 177             implementation. See <literal>ConditionVirtualization=</literal> in
 178             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 179             for details.
 180             </para>
 181           </listitem>
 182         </varlistentry>
 183         <varlistentry>
 184           <term><varname>KernelCommandLine=</varname></term>
 185           <listitem>
 186             <para>Checks whether a specific kernel command line option is
 187             set (or if prefixed with the exclamation mark unset). See
 188             <literal>ConditionKernelCommandLine=</literal> in
 189             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 190             for details.
 191             </para>
 192           </listitem>
 193         </varlistentry>
 194         <varlistentry>
 195           <term><varname>Architecture=</varname></term>
 196           <listitem>
 197             <para>Checks whether the system is running on a specific
 198             architecture. See <literal>ConditionArchitecture=</literal> in
 199             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 200             for details.
 201             </para>
 202           </listitem>
 203         </varlistentry>
 204       </variablelist>
 205
 206   </refsect1>
 207
 208   <refsect1>
 209     <title>[Link] Section Options</title>
 210
 211     <para> The <literal>[Link]</literal> section accepts the following keys:</para>
 212
 213     <variablelist class='network-directives'>
 214       <varlistentry>
 215         <term><varname>MACAddress=</varname></term>
 216         <listitem>
 217           <para>The hardware address to set for the device.</para>
 218         </listitem>
 219       </varlistentry>
 220       <varlistentry>
 221         <term><varname>MTUBytes=</varname></term>
 222         <listitem>
 223           <para>The maximum transmission unit in bytes to set for the
 224           device. The usual suffixes K, M, G, are supported and are
 225           understood to the base of 1024.</para>
 226           <para>Note that if IPv6 is enabled on the interface, and the MTU is chosen
 227           below 1280 (the minimum MTU for IPv6) it will automatically be increased to this value.</para>
 228         </listitem>
 229       </varlistentry>
 230       <varlistentry>
 231         <term><varname>ARP=</varname></term>
 232         <listitem>
 233           <para> A boolean. Enables or disables the ARP (low-level Address Resolution Protocol)
 234           for this interface. Defaults to unset, which means that the kernel default will be used.</para>
 235           <para> For example, disabling ARP is useful when creating multiple MACVLAN or VLAN virtual
 236           interfaces atop a single lower-level physical interface, which will then only serve as a
 237           link/"bridge" device aggregating traffic to the same physical link and not participate in
 238           the network otherwise.</para>
 239         </listitem>
 240       </varlistentry>
 241       <varlistentry>
 242         <term><varname>Unmanaged=</varname></term>
 243         <listitem>
 244           <para>A boolean. When <literal>yes</literal>, no attempts are
 245           made to bring up or configure matching links, equivalent to
 246           when there are no matching network files. Defaults to
 247           <literal>no</literal>.</para>
 248           <para>This is useful for preventing later matching network
 249           files from interfering with certain interfaces that are fully
 250           controlled by other applications.</para>
 251         </listitem>
 252       </varlistentry>
 253     </variablelist>
 254   </refsect1>
 255
 256   <refsect1>
 257     <title>[Network] Section Options</title>
 258
 259       <para>The <literal>[Network]</literal> section accepts the following keys:</para>
 260
 261       <variablelist class='network-directives'>
 262         <varlistentry>
 263           <term><varname>Description=</varname></term>
 264           <listitem>
 265             <para>A description of the device. This is only used for
 266             presentation purposes.</para>
 267           </listitem>
 268         </varlistentry>
 269         <varlistentry>
 270           <term><varname>DHCP=</varname></term>
 271           <listitem>
 272             <para>Enables DHCPv4 and/or DHCPv6 client support. Accepts
 273             <literal>yes</literal>, <literal>no</literal>,
 274             <literal>ipv4</literal>, or <literal>ipv6</literal>. Defaults
 275             to <literal>no</literal>.</para>
 276
 277             <para>Note that DHCPv6 will by default be triggered by Router
 278             Advertisement, if that is enabled, regardless of this parameter.
 279             By enabling DHCPv6 support explicitly, the DHCPv6 client will
 280             be started regardless of the presence of routers on the link,
 281             or what flags the routers pass. See
 282             <literal>IPv6AcceptRA=</literal>.</para>
 283
 284             <para>Furthermore, note that by default the domain name
 285             specified through DHCP is not used for name resolution.
 286             See option <option>UseDomains=</option> below.</para>
 287
 288             <para>See the <literal>[DHCP]</literal> section below for further configuration options for the DHCP client
 289             support.</para>
 290           </listitem>
 291         </varlistentry>
 292         <varlistentry>
 293           <term><varname>DHCPServer=</varname></term>
 294           <listitem>
 295             <para>A boolean. Enables DHCPv4 server support. Defaults
 296             to <literal>no</literal>. Further settings for the DHCP
 297             server may be set in the <literal>[DHCPServer]</literal>
 298             section described below.</para>
 299           </listitem>
 300         </varlistentry>
 301         <varlistentry>
 302           <term><varname>LinkLocalAddressing=</varname></term>
 303           <listitem>
 304             <para>Enables link-local address autoconfiguration. Accepts
 305             <literal>yes</literal>, <literal>no</literal>,
 306             <literal>ipv4</literal>, or <literal>ipv6</literal>. Defaults to
 307             <literal>ipv6</literal>.</para>
 308           </listitem>
 309         </varlistentry>
 310         <varlistentry>
 311           <term><varname>IPv4LLRoute=</varname></term>
 312           <listitem>
 313             <para>A boolean. When true, sets up the route needed for
 314             non-IPv4LL hosts to communicate with IPv4LL-only hosts. Defaults
 315             to false.
 316             </para>
 317           </listitem>
 318         </varlistentry>
 319         <varlistentry>
 320           <term><varname>IPv6Token=</varname></term>
 321           <listitem>
 322             <para>An IPv6 address with the top 64 bits unset. When set, indicates the
 323             64-bit interface part of SLAAC IPv6 addresses for this link. Note that
 324             the token is only ever used for SLAAC, and not for DHCPv6 addresses, even
 325             in the case DHCP is requested by router advertisement. By default, the
 326             token is autogenerated.</para>
 327           </listitem>
 328         </varlistentry>
 329         <varlistentry>
 330           <term><varname>LLMNR=</varname></term>
 331           <listitem>
 332             <para>A boolean or <literal>resolve</literal>. When true,
 333             enables <ulink
 334             url="https://tools.ietf.org/html/rfc4795">Link-Local
 335             Multicast Name Resolution</ulink> on the link. When set to
 336             <literal>resolve</literal>, only resolution is enabled,
 337             but not host registration and announcement. Defaults to
 338             true. This setting is read by
 339             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 340           </listitem>
 341         </varlistentry>
 342         <varlistentry>
 343           <term><varname>MulticastDNS=</varname></term>
 344           <listitem>
 345             <para>A boolean or <literal>resolve</literal>. When true,
 346             enables <ulink
 347             url="https://tools.ietf.org/html/rfc6762">Multicast
 348             DNS</ulink> support on the link. When set to
 349             <literal>resolve</literal>, only resolution is enabled,
 350             but not host or service registration and
 351             announcement. Defaults to false. This setting is read by
 352             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 353           </listitem>
 354         </varlistentry>
 355         <varlistentry>
 356           <term><varname>DNSSEC=</varname></term>
 357           <listitem>
 358             <para>A boolean or
 359             <literal>allow-downgrade</literal>. When true, enables
 360             <ulink
 361             url="https://tools.ietf.org/html/rfc4033">DNSSEC</ulink>
 362             DNS validation support on the link. When set to
 363             <literal>allow-downgrade</literal>, compatibility with
 364             non-DNSSEC capable networks is increased, by automatically
 365             turning off DNSSEC in this case. This option defines a
 366             per-interface setting for
 367             <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>'s
 368             global <varname>DNSSEC=</varname> option. Defaults to
 369             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>DNSSECNegativeTrustAnchors=</varname></term>
 375           <listitem><para>A space-separated list of DNSSEC negative
 376           trust anchor domains. If specified and DNSSEC is enabled,
 377           look-ups done via the interface's DNS server will be subject
 378           to the list of negative trust anchors, and not require
 379           authentication for the specified domains, or anything below
 380           it. Use this to disable DNSSEC authentication for specific
 381           private domains, that cannot be proven valid using the
 382           Internet DNS hierarchy. Defaults to the empty list. This
 383           setting is read by
 384           <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 385           </listitem>
 386         </varlistentry>
 387         <varlistentry>
 388           <term><varname>LLDP=</varname></term>
 389           <listitem>
 390             <para>Controls support for Ethernet LLDP packet reception. LLDP is a link-layer protocol commonly
 391             implemented on professional routers and bridges which announces which physical port a system is connected
 392             to, as well as other related data. Accepts a boolean or the special value
 393             <literal>routers-only</literal>. When true, incoming LLDP packets are accepted and a database of all LLDP
 394             neighbors maintained. If <literal>routers-only</literal> is set only LLDP data of various types of routers
 395             is collected and LLDP data about other types of devices ignored (such as stations, telephones and
 396             others). If false, LLDP reception is disabled. Defaults to <literal>routers-only</literal>. Use
 397             <citerefentry><refentrytitle>networkctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> to query the
 398             collected neighbor data. LLDP is only available on Ethernet links. See <varname>EmitLLDP=</varname> below
 399             for enabling LLDP packet emission from the local system.
 400             </para>
 401           </listitem>
 402         </varlistentry>
 403         <varlistentry>
 404           <term><varname>EmitLLDP=</varname></term>
 405           <listitem>
 406             <para>Controls support for Ethernet LLDP packet emission. Accepts a boolean parameter or the special values
 407             <literal>nearest-bridge</literal>, <literal>non-tpmr-bridge</literal> and
 408             <literal>customer-bridge</literal>.  Defaults to false, which turns off LLDP packet emission. If not false,
 409             a short LLDP packet with information about the local system is sent out in regular intervals on the
 410             link. The LLDP packet will contain information about the local host name, the local machine ID (as stored
 411             in <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>) and the
 412             local interface name, as well as the pretty hostname of the system (as set in
 413             <citerefentry><refentrytitle>machine-info</refentrytitle><manvolnum>5</manvolnum></citerefentry>). LLDP
 414             emission is only available on Ethernet links. Note that this setting passes data suitable for
 415             identification of host to the network and should thus not be enabled on untrusted networks, where such
 416             identification data should not be made available. Use this option to permit other systems to identify on
 417             which interfaces they are connected to this system. The three special values control propagation of the
 418             LLDP packets. The <literal>nearest-bridge</literal> setting permits propagation only to the nearest
 419             connected bridge, <literal>non-tpmr-bridge</literal> permits propagation across Two-Port MAC Relays, but
 420             not any other bridges, and <literal>customer-bridge</literal> permits propagation until a customer bridge
 421             is reached. For details about these concepts, see <ulink
 422             url="http://standards.ieee.org/getieee802/download/802.1AB-2009.pdf">IEEE 802.1AB-2009</ulink>. Note that
 423             configuring this setting to true is equivalent to <literal>nearest-bridge</literal>, the recommended and
 424             most restricted level of propagation. See <varname>LLDP=</varname> above for an option to enable LLDP
 425             reception.</para>
 426           </listitem>
 427         </varlistentry>
 428         <varlistentry>
 429           <term><varname>BindCarrier=</varname></term>
 430           <listitem>
 431             <para>A link name or a list of link names. When set, controls the behavior of the current
 432             link. When all links in the list are in an operational down state, the current link is brought
 433             down. When at least one link has carrier, the current interface is brought up.
 434             </para>
 435           </listitem>
 436         </varlistentry>
 437         <varlistentry>
 438           <term><varname>Address=</varname></term>
 439           <listitem>
 440             <para>A static IPv4 or IPv6 address and its prefix length,
 441             separated by a <literal>/</literal> character. Specify
 442             this key more than once to configure several addresses.
 443             The format of the address must be as described in
 444             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 445             This is a short-hand for an [Address] section only
 446             containing an Address key (see below). This option may be
 447             specified more than once.
 448             </para>
 449
 450             <para>If the specified address is 0.0.0.0 (for IPv4) or
 451             [::] (for IPv6), a new address range of the requested size
 452             is automatically allocated from a system-wide pool of
 453             unused ranges. The allocated range is checked against all
 454             current network interfaces and all known network
 455             configuration files to avoid address range conflicts. The
 456             default system-wide pool consists of 192.168.0.0/16,
 457             172.16.0.0/12 and 10.0.0.0/8 for IPv4, and fc00::/7 for
 458             IPv6. This functionality is useful to manage a large
 459             number of dynamically created network interfaces with the
 460             same network configuration and automatic address range
 461             assignment.</para>
 462
 463           </listitem>
 464         </varlistentry>
 465         <varlistentry>
 466           <term><varname>Gateway=</varname></term>
 467           <listitem>
 468             <para>The gateway address, which must be in the format
 469             described in
 470             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 471             This is a short-hand for a [Route] section only containing
 472             a Gateway key. This option may be specified more than
 473             once.</para>
 474           </listitem>
 475         </varlistentry>
 476         <varlistentry>
 477           <term><varname>DNS=</varname></term>
 478           <listitem>
 479             <para>A DNS server address, which must be in the format
 480             described in
 481             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 482             This option may be specified more than once. This setting is read by
 483             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 484           </listitem>
 485         </varlistentry>
 486         <varlistentry>
 487           <term><varname>Domains=</varname></term>
 488           <listitem>
 489             <para>A list of domains which should be resolved using the DNS servers on this link. Each item in the list
 490             should be a domain name, optionally prefixed with a tilde (<literal>~</literal>). The domains with the
 491             prefix are called "routing-only domains". The domains without the prefix are called "search domains" and
 492             are first used as search suffixes for extending single-label host names (host names containing no dots) to
 493             become fully qualified domain names (FQDNs). If a single-label host name is resolved on this interface,
 494             each of the specified search domains are appended to it in turn, converting it into a fully qualified
 495             domain name, until one of them may be successfully resolved.</para>
 496
 497             <para>Both "search" and "routing-only" domains are used for routing of DNS queries: look-ups for host names
 498             ending in those domains (hence also single label names, if any "search domains" are listed), are routed to
 499             the DNS servers configured for this interface. The domain routing logic is particularly useful on
 500             multi-homed hosts with DNS servers serving particular private DNS zones on each interface.</para>
 501
 502             <para>The "routing-only" domain <literal>~.</literal> (the tilde indicating definition of a routing domain,
 503             the dot referring to the DNS root domain which is the implied suffix of all valid DNS names) has special
 504             effect. It causes all DNS traffic which does not match another configured domain routing entry to be routed
 505             to DNS servers specified for this interface. This setting is useful to prefer a certain set of DNS servers
 506             if a link on which they are connected is available.</para>
 507
 508             <para>This setting is read by
 509             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
 510             "Search domains" correspond to the <varname>domain</varname> and <varname>search</varname> entries in
 511             <citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 512             Domain name routing has no equivalent in the traditional glibc API, which has no concept of domain
 513             name servers limited to a specific link.</para>
 514           </listitem>
 515         </varlistentry>
 516         <varlistentry>
 517           <term><varname>NTP=</varname></term>
 518           <listitem>
 519             <para>An NTP server address. This option may be specified more than once. This setting is read by
 520             <citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 521           </listitem>
 522         </varlistentry>
 523         <varlistentry>
 524           <term><varname>IPForward=</varname></term>
 525           <listitem><para>Configures IP packet forwarding for the
 526           system. If enabled, incoming packets on any network
 527           interface will be forwarded to any other interfaces
 528           according to the routing table. Takes either a boolean
 529           argument, or the values <literal>ipv4</literal> or
 530           <literal>ipv6</literal>, which only enable IP packet
 531           forwarding for the specified address family.  This controls
 532           the <filename>net.ipv4.ip_forward</filename> and
 533           <filename>net.ipv6.conf.all.forwarding</filename> sysctl
 534           options of the network interface (see <ulink
 535           url="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">ip-sysctl.txt</ulink>
 536           for details about sysctl options). Defaults to
 537           <literal>no</literal>.</para>
 538
 539           <para>Note: this setting controls a global kernel option,
 540           and does so one way only: if a network that has this setting
 541           enabled is set up the global setting is turned on.  However,
 542           it is never turned off again, even after all networks with
 543           this setting enabled are shut down again.</para>
 544
 545           <para>To allow IP packet forwarding only between specific
 546           network interfaces use a firewall.</para>
 547           </listitem>
 548         </varlistentry>
 549         <varlistentry>
 550           <term><varname>IPMasquerade=</varname></term>
 551           <listitem><para>Configures IP masquerading for the network
 552           interface. If enabled, packets forwarded from the network
 553           interface will be appear as coming from the local host.
 554           Takes a boolean argument. Implies
 555           <varname>IPForward=ipv4</varname>. Defaults to
 556           <literal>no</literal>.</para></listitem>
 557         </varlistentry>
 558         <varlistentry>
 559           <term><varname>IPv6PrivacyExtensions=</varname></term>
 560           <listitem><para>Configures use of stateless temporary
 561           addresses that change over time (see <ulink
 562           url="https://tools.ietf.org/html/rfc4941">RFC 4941</ulink>,
 563           Privacy Extensions for Stateless Address Autoconfiguration
 564           in IPv6). Takes a boolean or the special values
 565           <literal>prefer-public</literal> and
 566           <literal>kernel</literal>. When true, enables the privacy
 567           extensions and prefers temporary addresses over public
 568           addresses. When <literal>prefer-public</literal>, enables the
 569           privacy extensions, but prefers public addresses over
 570           temporary addresses. When false, the privacy extensions
 571           remain disabled. When <literal>kernel</literal>, the kernel's
 572           default setting will be left in place.  Defaults to
 573           <literal>no</literal>.</para></listitem>
 574         </varlistentry>
 575         <varlistentry>
 576           <term><varname>IPv6AcceptRA=</varname></term>
 577           <listitem><para>Enable or disable IPv6 Router Advertisement (RA) reception support for the interface.  Takes
 578           a boolean parameter. If true, RAs are accepted; if false, RAs are ignored, independently of the local
 579           forwarding state. When not set, the kernel default is used, and RAs are accepted only when local forwarding
 580           is disabled for that interface.  When RAs are accepted, they may trigger the start of the DHCPv6 client if
 581           the relevant flags are set in the RA data, or if no routers are found on the link.</para>
 582
 583           <para>Further settings for the IPv6 RA support may be configured in the
 584           <literal>[IPv6AcceptRA]</literal> section, see below.</para>
 585
 586           <para>Also see <ulink
 587           url="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">ip-sysctl.txt</ulink> in the kernel
 588           documentation regarding <literal>accept_ra</literal>, but note that systemd's setting of
 589           <constant>1</constant> (i.e. true) corresponds to kernel's setting of <constant>2</constant>.</para>
 590         </listitem>
 591         </varlistentry>
 592         <varlistentry>
 593           <term><varname>IPv6DuplicateAddressDetection=</varname></term>
 594           <listitem><para>Configures the amount of IPv6 Duplicate
 595           Address Detection (DAD) probes to send. Defaults to unset.
 596         </para></listitem>
 597         </varlistentry>
 598         <varlistentry>
 599           <term><varname>IPv6HopLimit=</varname></term>
 600           <listitem><para>Configures IPv6 Hop Limit. For each router that
 601           forwards the packet, the hop limit is decremented by 1. When the
 602           hop limit field reaches zero, the packet is discarded.
 603           Defaults to unset.
 604         </para></listitem>
 605         </varlistentry>
 606         <varlistentry>
 607           <term><varname>IPv4ProxyARP=</varname></term>
 608           <listitem><para>A boolean. Configures proxy ARP for IPv4. Proxy ARP is the technique in which one host,
 609           usually a router, answers ARP requests intended for another machine. By "faking" its identity,
 610           the router accepts responsibility for routing packets to the "real" destination. (see <ulink
 611           url="https://tools.ietf.org/html/rfc1027">RFC 1027</ulink>.
 612           Defaults to unset.
 613         </para></listitem>
 614         </varlistentry>
 615         <varlistentry>
 616           <term><varname>IPv6ProxyNDP=</varname></term>
 617           <listitem><para>A boolean. Configures proxy NDP for IPv6. Proxy NDP (Neighbor Discovery
 618           Protocol) is a technique for IPv6 to allow routing of addresses to a different
 619           destination when peers expect them to be present on a certain physical link.
 620           In this case a router answers Neighbour Advertisement messages intended for
 621           another machine by offering its own MAC address as destination.
 622           Unlike proxy ARP for IPv4, it is not enabled globally, but will only send Neighbour
 623           Advertisement messages for addresses in the IPv6 neighbor proxy table,
 624           which can also be shown by <command>ip -6 neighbour show proxy</command>.
 625           systemd-networkd will control the per-interface `proxy_ndp` switch for each configured
 626           interface depending on this option.
 627           Defautls to unset.
 628         </para></listitem>
 629         </varlistentry>
 630         <varlistentry>
 631           <term><varname>IPv6ProxyNDPAddress=</varname></term>
 632           <listitem><para>An IPv6 address, for which Neighbour Advertisement messages will be
 633           proxied. This option may be specified more than once. systemd-networkd will add the
 634           <option>IPv6ProxyNDPAddress=</option> entries to the kernel's IPv6 neighbor proxy table.
 635           This option implies <option>IPv6ProxyNDP=true</option> but has no effect if
 636           <option>IPv6ProxyNDP</option> has been set to false. Defaults to unset.
 637         </para></listitem>
 638         </varlistentry>
 639         <varlistentry>
 640           <term><varname>IPv6PrefixDelegation=</varname></term>
 641           <listitem><para>Whether to enable or disable Router Advertisement sending on a link.
 642           Defaults to <literal>false</literal>. See the <literal>[IPv6PrefixDelegation]</literal>
 643           and the <literal>[IPv6Prefix]</literal> sections for configuration options.
 644           </para></listitem>
 645         </varlistentry>
 646         <varlistentry>
 647           <term><varname>Bridge=</varname></term>
 648           <listitem>
 649             <para>The name of the bridge to add the link to. See
 650             <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 651             </para>
 652           </listitem>
 653         </varlistentry>
 654         <varlistentry>
 655           <term><varname>Bond=</varname></term>
 656           <listitem>
 657             <para>The name of the bond to add the link to. See
 658             <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 659             </para>
 660           </listitem>
 661         </varlistentry>
 662         <varlistentry>
 663           <term><varname>VRF=</varname></term>
 664           <listitem>
 665             <para>The name of the VRF to add the link to. See
 666             <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 667             </para>
 668           </listitem>
 669         </varlistentry>
 670         <varlistentry>
 671           <term><varname>VLAN=</varname></term>
 672           <listitem>
 673             <para>The name of a VLAN to create on the link. See
 674             <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 675             This option may be specified more than once.</para>
 676           </listitem>
 677         </varlistentry>
 678         <varlistentry>
 679           <term><varname>MACVLAN=</varname></term>
 680           <listitem>
 681             <para>The name of a MACVLAN to create on the link. See
 682             <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 683             This option may be specified more than once.</para>
 684           </listitem>
 685         </varlistentry>
 686         <varlistentry>
 687           <term><varname>VXLAN=</varname></term>
 688           <listitem>
 689             <para>The name of a VXLAN to create on the link. See
 690             <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 691             This option may be specified more than once.</para>
 692           </listitem>
 693         </varlistentry>
 694         <varlistentry>
 695           <term><varname>Tunnel=</varname></term>
 696           <listitem>
 697             <para>The name of a Tunnel to create on the link. See
 698             <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 699             This option may be specified more than once.</para>
 700           </listitem>
 701         </varlistentry>
 702       <varlistentry>
 703         <term><varname>ActiveSlave=</varname></term>
 704         <listitem>
 705           <para>A boolean. Specifies the new active slave. The <literal>ActiveSlave=</literal>
 706           option is only valid for following modes:
 707           <literal>active-backup</literal>,
 708           <literal>balance-alb</literal> and
 709           <literal>balance-tlb</literal>. Defaults to false.
 710           </para>
 711         </listitem>
 712       </varlistentry>
 713       <varlistentry>
 714         <term><varname>PrimarySlave=</varname></term>
 715         <listitem>
 716           <para>A boolean. Specifies which slave is the primary device. The specified
 717           device will always be the active slave while it is available. Only when the
 718           primary is off-line will alternate devices be used.  This is useful when
 719           one slave is preferred over another, e.g. when one slave has higher throughput
 720           than another. The <literal>PrimarySlave=</literal> option is only valid for
 721           following modes:
 722           <literal>active-backup</literal>,
 723           <literal>balance-alb</literal> and
 724           <literal>balance-tlb</literal>. Defaults to false.
 725           </para>
 726         </listitem>
 727       </varlistentry>
 728       <varlistentry>
 729         <term><varname>ConfigureWithoutCarrier=</varname></term>
 730         <listitem>
 731           <para>A boolean. Allows networkd to configure a specific link even if it has no carrier.
 732           Defaults to false.
 733           </para>
 734         </listitem>
 735       </varlistentry>
 736       </variablelist>
 737
 738   </refsect1>
 739
 740   <refsect1>
 741     <title>[Address] Section Options</title>
 742
 743       <para>An <literal>[Address]</literal> section accepts the
 744       following keys. Specify several <literal>[Address]</literal>
 745       sections to configure several addresses.</para>
 746
 747       <variablelist class='network-directives'>
 748         <varlistentry>
 749           <term><varname>Address=</varname></term>
 750           <listitem>
 751             <para>As in the <literal>[Network]</literal> section. This
 752             key is mandatory.</para>
 753           </listitem>
 754         </varlistentry>
 755         <varlistentry>
 756           <term><varname>Peer=</varname></term>
 757           <listitem>
 758             <para>The peer address in a point-to-point connection.
 759             Accepts the same format as the <literal>Address</literal>
 760             key.</para>
 761           </listitem>
 762         </varlistentry>
 763         <varlistentry>
 764           <term><varname>Broadcast=</varname></term>
 765           <listitem>
 766             <para>The broadcast address, which must be in the format
 767             described in
 768             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 769             This key only applies to IPv4 addresses. If it is not
 770             given, it is derived from the <literal>Address</literal>
 771             key.</para>
 772           </listitem>
 773         </varlistentry>
 774         <varlistentry>
 775           <term><varname>Label=</varname></term>
 776           <listitem>
 777             <para>An address label.</para>
 778           </listitem>
 779         </varlistentry>
 780         <varlistentry>
 781           <term><varname>PreferredLifetime=</varname></term>
 782           <listitem>
 783             <para>Allows the default "preferred lifetime" of the address to be overridden.
 784             Only three settings are accepted: <literal>forever</literal> or <literal>infinity</literal>
 785             which is the default and means that the address never expires, and <literal>0</literal> which means
 786             that the address is considered immediately "expired" and will not be used,
 787             unless explicitly requested. A setting of PreferredLifetime=0 is useful for
 788             addresses which are added to be used only by a specific application,
 789             which is then configured to use them explicitly.</para>
 790           </listitem>
 791         </varlistentry>
 792         <varlistentry>
 793           <term><varname>Scope=</varname></term>
 794           <listitem>
 795             <para>The scope of the address, which can be <literal>global</literal>,
 796             <literal>link</literal> or <literal>host</literal> or an unsigned integer ranges 0 to 255.
 797             Defaults to <literal>global</literal>.</para>
 798           </listitem>
 799         </varlistentry>
 800         <varlistentry>
 801           <term><varname>HomeAddress=</varname></term>
 802           <listitem>
 803             <para>Takes a boolean argument. Designates this address the "home address" as defined in
 804             <ulink url="https://tools.ietf.org/html/rfc6275">RFC 6275</ulink>.
 805             Supported only on IPv6. Defaults to false.</para>
 806           </listitem>
 807         </varlistentry>
 808         <varlistentry>
 809           <term><varname>DuplicateAddressDetection=</varname></term>
 810           <listitem>
 811             <para>Takes a boolean argument. Do not perform Duplicate Address Detection
 812             <ulink url="https://tools.ietf.org/html/rfc4862">RFC 4862</ulink> when adding this address.
 813             Supported only on IPv6. Defaults to false.</para>
 814           </listitem>
 815         </varlistentry>
 816         <varlistentry>
 817           <term><varname>ManageTemporaryAddress=</varname></term>
 818           <listitem>
 819             <para>Takes a boolean argument. If true the kernel manage temporary addresses created
 820             from this one as template on behalf of Privacy Extensions
 821             <ulink url="https://tools.ietf.org/html/rfc3041">RFC 3041</ulink>.  For this to become
 822             active, the use_tempaddr sysctl setting has to be set to a value greater than zero.
 823             The given address needs to have a prefix length of 64. This flag allows to use privacy
 824             extensions in a manually configured network, just like if stateless auto-configuration
 825             was active. Defaults to false. </para>
 826           </listitem>
 827         </varlistentry>
 828         <varlistentry>
 829           <term><varname>PrefixRoute=</varname></term>
 830           <listitem>
 831             <para>Takes a boolean argument. When adding or modifying an IPv6 address, the userspace
 832             application needs a way to suppress adding a prefix route. This is for example relevant
 833             together with IFA_F_MANAGERTEMPADDR, where userspace creates autoconf generated addresses,
 834             but depending on on-link, no route for the prefix should be added. Defaults to false.</para>
 835           </listitem>
 836         </varlistentry>
 837         <varlistentry>
 838           <term><varname>AutoJoin=</varname></term>
 839           <listitem>
 840             <para>Takes a boolean argument. Joining multicast group on ethernet level via
 841             <command>ip maddr</command> command would not work if we have an Ethernet switch that does
 842             IGMP snooping since the switch would not replicate multicast packets on  ports that did not
 843             have IGMP reports for the multicast addresses. Linux vxlan interfaces created via
 844             <command>ip link add vxlan</command> or networkd's netdev kind vxlan have the group option
 845             that enables then to do the required join. By extending ip address command with option
 846             <literal>autojoin</literal> we can get similar functionality for openvswitch (OVS) vxlan
 847             interfaces as well as other tunneling mechanisms that need to receive multicast traffic.
 848             Defaults to <literal>no</literal>.</para>
 849           </listitem>
 850         </varlistentry>
 851       </variablelist>
 852   </refsect1>
 853
 854     <refsect1>
 855     <title>[IPv6AddressLabel] Section Options</title>
 856
 857       <para>An <literal>[IPv6AddressLabel]</literal> section accepts the
 858       following keys. Specify several <literal>[IPv6AddressLabel]</literal>
 859       sections to configure several address labels. IPv6 address labels are
 860       used for address selection. See <ulink url="https://tools.ietf.org/html/rfc3484">RFC 3484</ulink>.
 861       Precedence is managed by userspace, and only the label itself is stored in the kernel</para>
 862
 863       <variablelist class='network-directives'>
 864         <varlistentry>
 865           <term><varname>Label=</varname></term>
 866           <listitem>
 867             <para> The label for the prefix (an unsigned integer) ranges 0 to 4294967294.
 868             0xffffffff is reserved. This key is mandatory.</para>
 869           </listitem>
 870         </varlistentry>
 871         <varlistentry>
 872           <term><varname>Prefix=</varname></term>
 873           <listitem>
 874             <para>IPv6 prefix is an address with a prefix length, separated by a slash <literal>/</literal> character.
 875             This key is mandatory. </para>
 876           </listitem>
 877         </varlistentry>
 878       </variablelist>
 879   </refsect1>
 880
 881  <refsect1>
 882     <title>[RoutingPolicyRule] Section Options</title>
 883
 884       <para>An <literal>[RoutingPolicyRule]</literal> section accepts the
 885       following keys. Specify several <literal>[RoutingPolicyRule]</literal>
 886       sections to configure several rules.</para>
 887
 888       <variablelist class='network-directives'>
 889         <varlistentry>
 890           <term><varname>TypeOfService=</varname></term>
 891           <listitem>
 892             <para>Specifies the type of service to match a number between 0 to 255.</para>
 893           </listitem>
 894         </varlistentry>
 895         <varlistentry>
 896           <term><varname>From=</varname></term>
 897           <listitem>
 898             <para>Specifies the source address prefix to match. Possibly followed by a slash and the prefix length.</para>
 899           </listitem>
 900         </varlistentry>
 901         <varlistentry>
 902           <term><varname>To=</varname></term>
 903           <listitem>
 904             <para>Specifies the destination address prefix to match. Possibly followed by a slash and the prefix length.</para>
 905           </listitem>
 906         </varlistentry>
 907         <varlistentry>
 908           <term><varname>FirewallMark=</varname></term>
 909           <listitem>
 910             <para>Specifies the iptables firewall mark value to match (a number between 1 and 4294967295).</para>
 911           </listitem>
 912         </varlistentry>
 913         <varlistentry>
 914           <term><varname>Table=</varname></term>
 915           <listitem>
 916             <para>Specifies the routing table identifier to lookup if the rule
 917             selector matches. The table identifier for a route (a number between 1 and 4294967295).</para>
 918           </listitem>
 919         </varlistentry>
 920         <varlistentry>
 921           <term><varname>Priority=</varname></term>
 922           <listitem>
 923             <para>Specifies the priority of this rule. <varname>Priority=</varname> is an unsigned
 924             integer. Higher number means lower priority, and rules get processed in order of increasing number.</para>
 925           </listitem>
 926         </varlistentry>
 927       </variablelist>
 928   </refsect1>
 929
 930   <refsect1>
 931     <title>[Route] Section Options</title>
 932       <para>The <literal>[Route]</literal> section accepts the
 933       following keys. Specify several <literal>[Route]</literal>
 934       sections to configure several routes.</para>
 935
 936       <variablelist class='network-directives'>
 937         <varlistentry>
 938           <term><varname>Gateway=</varname></term>
 939           <listitem>
 940             <para>As in the <literal>[Network]</literal> section.</para>
 941           </listitem>
 942         </varlistentry>
 943          <varlistentry>
 944            <term><varname>GatewayOnlink=</varname></term>
 945            <listitem>
 946              <para>The <literal>GatewayOnlink</literal> option tells the kernel that it does not have
 947              to check if the gateway is reachable directly by the current machine (i.e., the kernel does
 948              not need to check if the gateway is attached to the local network), so that we can insert the
 949              route in the kernel table without it being complained about. A boolean, defaults to <literal>no</literal>.
 950              </para>
 951            </listitem>
 952          </varlistentry>
 953         <varlistentry>
 954           <term><varname>Destination=</varname></term>
 955           <listitem>
 956             <para>The destination prefix of the route. Possibly
 957             followed by a slash and the prefix length. If omitted, a
 958             full-length host route is assumed.</para>
 959           </listitem>
 960         </varlistentry>
 961         <varlistentry>
 962           <term><varname>Source=</varname></term>
 963           <listitem>
 964             <para>The source prefix of the route. Possibly followed by
 965             a slash and the prefix length. If omitted, a full-length
 966             host route is assumed.</para>
 967           </listitem>
 968         </varlistentry>
 969         <varlistentry>
 970           <term><varname>Metric=</varname></term>
 971           <listitem>
 972             <para>The metric of the route (an unsigned integer).</para>
 973           </listitem>
 974         </varlistentry>
 975         <varlistentry>
 976           <term><varname>IPv6Preference=</varname></term>
 977           <listitem>
 978             <para>Specifies the route preference as defined in <ulink
 979             url="https://tools.ietf.org/html/rfc4191">RFC4191</ulink> for Router Discovery messages.
 980             Which can be one of <literal>low</literal> the route has a lowest priority,
 981             <literal>medium</literal> the route has a default priority or
 982             <literal>high</literal> the route has a highest priority.</para>
 983           </listitem>
 984         </varlistentry>
 985         <varlistentry>
 986           <term><varname>Scope=</varname></term>
 987           <listitem>
 988             <para>The scope of the route, which can be <literal>global</literal>,
 989             <literal>link</literal> or <literal>host</literal>. Defaults to
 990             <literal>global</literal>.</para>
 991           </listitem>
 992         </varlistentry>
 993         <varlistentry>
 994           <term><varname>PreferredSource=</varname></term>
 995           <listitem>
 996             <para>The preferred source address of the route. The address
 997             must be in the format described in
 998             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
 999           </listitem>
1000         </varlistentry>
1001         <varlistentry>
1002           <term><varname>Table=<replaceable>num</replaceable></varname></term>
1003           <listitem>
1004           <para>The table identifier for the route (a number between 1 and 4294967295, or 0 to unset).
1005           The table can be retrieved using <command>ip route show table <replaceable>num</replaceable></command>.
1006           </para>
1007           </listitem>
1008         </varlistentry>
1009         <varlistentry>
1010           <term><varname>Protocol=</varname></term>
1011           <listitem>
1012             <para>The Protocol identifier for the route. Takes a number between 0 and 255 or the special values
1013             <literal>kernel</literal>, <literal>boot</literal> and <literal>static</literal>. Defaults to
1014             <literal>static</literal>.
1015             </para>
1016           </listitem>
1017         </varlistentry>
1018         <varlistentry>
1019           <term><varname>Type=</varname></term>
1020           <listitem>
1021             <para>The Type identifier for special route types, which can be
1022             <literal>unicast</literal> route to a destination network address which describes the path to the destination,
1023             <literal>blackhole</literal> packets are discarded silently,
1024             <literal>unreachable</literal> packets are discarded and the ICMP message host unreachable is generated,
1025             <literal>prohibit</literal> packets are discarded and the ICMP message communication administratively
1026             prohibited is generated. Defaults to <literal>unicast</literal>.
1027             </para>
1028           </listitem>
1029         </varlistentry>
1030
1031       </variablelist>
1032   </refsect1>
1033
1034   <refsect1>
1035     <title>[DHCP] Section Options</title>
1036       <para>The <literal>[DHCP]</literal> section configures the
1037       DHCPv4 and DHCP6 client, if it is enabled with the
1038       <varname>DHCP=</varname> setting described above:</para>
1039
1040       <variablelist class='network-directives'>
1041         <varlistentry>
1042           <term><varname>UseDNS=</varname></term>
1043           <listitem>
1044             <para>When true (the default), the DNS servers received
1045             from the DHCP server will be used and take precedence over
1046             any statically configured ones.</para>
1047
1048             <para>This corresponds to the <option>nameserver</option>
1049             option in <citerefentry
1050             project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
1051           </listitem>
1052         </varlistentry>
1053         <varlistentry>
1054           <term><varname>UseNTP=</varname></term>
1055           <listitem>
1056             <para>When true (the default), the NTP servers received
1057             from the DHCP server will be used by systemd-timesyncd
1058             and take precedence over any statically configured ones.</para>
1059           </listitem>
1060         </varlistentry>
1061         <varlistentry>
1062           <term><varname>UseMTU=</varname></term>
1063           <listitem>
1064             <para>When true, the interface maximum transmission unit
1065             from the DHCP server will be used on the current link.
1066             Defaults to false.</para>
1067           </listitem>
1068         </varlistentry>
1069         <varlistentry>
1070           <term><varname>Anonymize=</varname></term>
1071           <listitem>
1072             <para>Takes a boolean argument. When true, the options sent to the DHCP server will
1073             follow the <ulink url="https://tools.ietf.org/html/rfc7844">RFC 7844</ulink>
1074             (Anonymity Profiles for DHCP Clients) to minimize disclosure of identifying information.
1075             Defaults to false.</para>
1076
1077             <para>This option should only be set to true when
1078             <varname>MACAddressPolicy=</varname> is set to <literal>random</literal>
1079             (see <citerefentry
1080             project='man-pages'><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para>
1081
1082             <para>Note that this configuration will overwrite others.
1083             In concrete, the following variables will be ignored:
1084             <varname>SendHostname=</varname>, <varname>ClientIdentifier=</varname>,
1085             <varname>UseRoutes=</varname>, <varname>SendHostname=</varname>,
1086             <varname>UseMTU=</varname>, <varname>VendorClassIdentifier=</varname>,
1087             <varname>UseTimezone=</varname>.</para>
1088           </listitem>
1089         </varlistentry>
1090         <varlistentry>
1091           <term><varname>SendHostname=</varname></term>
1092           <listitem>
1093             <para>When true (the default), the machine's hostname will
1094             be sent to the DHCP server.</para>
1095           </listitem>
1096         </varlistentry>
1097         <varlistentry>
1098           <term><varname>UseHostname=</varname></term>
1099           <listitem>
1100             <para>When true (the default), the hostname received from
1101             the DHCP server will be set as the transient hostname of the system
1102             </para>
1103           </listitem>
1104         </varlistentry>
1105         <varlistentry>
1106         <term><varname>Hostname=</varname></term>
1107         <listitem>
1108           <para>Use this value for the hostname which is sent to the
1109           DHCP server, instead of machine's hostname.</para>
1110         </listitem>
1111       </varlistentry>
1112         <varlistentry>
1113           <term><varname>UseDomains=</varname></term>
1114           <listitem>
1115             <para>Takes a boolean argument, or the special value <literal>route</literal>. When true, the domain name
1116             received from the DHCP server will be used as DNS search domain over this link, similar to the effect of
1117             the <option>Domains=</option> setting. If set to <literal>route</literal>, the domain name received from
1118             the DHCP server will be used for routing DNS queries only, but not for searching, similar to the effect of
1119             the <option>Domains=</option> setting when the argument is prefixed with <literal>~</literal>. Defaults to
1120             false.</para>
1121
1122             <para>It is recommended to enable this option only on trusted networks, as setting this affects resolution
1123             of all host names, in particular of single-label names. It is generally safer to use the supplied domain
1124             only as routing domain, rather than as search domain, in order to not have it affect local resolution of
1125             single-label names.</para>
1126
1127             <para>When set to true, this setting corresponds to the <option>domain</option> option in <citerefentry
1128             project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
1129           </listitem>
1130         </varlistentry>
1131         <varlistentry>
1132           <term><varname>UseRoutes=</varname></term>
1133           <listitem>
1134             <para>When true (the default), the static routes will be requested from the DHCP server and added to the
1135               routing table with a metric of 1024, and a scope of "global", "link" or "host", depending on the route's
1136               destination and gateway. If the destination is on the local host, e.g., 127.x.x.x, or the same as the
1137               link's own address, the scope will be set to "host". Otherwise if the gateway is null (a direct route), a
1138               "link" scope will be used. For anything else, scope defaults to "global".</para>
1139           </listitem>
1140         </varlistentry>
1141
1142         <varlistentry>
1143           <term><varname>UseTimezone=</varname></term>
1144
1145           <listitem><para>When true, the timezone received from the
1146           DHCP server will be set as timezone of the local
1147           system. Defaults to <literal>no</literal>.</para></listitem>
1148         </varlistentry>
1149
1150         <varlistentry>
1151           <term><varname>CriticalConnection=</varname></term>
1152           <listitem>
1153             <para>When true, the connection will never be torn down
1154             even if the DHCP lease expires. This is contrary to the
1155             DHCP specification, but may be the best choice if, say,
1156             the root filesystem relies on this connection. Defaults to
1157             false.</para>
1158           </listitem>
1159         </varlistentry>
1160
1161         <varlistentry>
1162           <term><varname>ClientIdentifier=</varname></term>
1163           <listitem>
1164             <para>The DHCPv4 client identifier to use. Either <literal>mac</literal> to use the MAC address of the link
1165             or <literal>duid</literal> (the default, see below) to use an RFC4361-compliant Client ID.</para>
1166           </listitem>
1167         </varlistentry>
1168
1169         <varlistentry>
1170           <term><varname>VendorClassIdentifier=</varname></term>
1171           <listitem>
1172             <para>The vendor class identifier used to identify vendor
1173             type and configuration.</para>
1174           </listitem>
1175         </varlistentry>
1176
1177         <varlistentry>
1178           <term><varname>DUIDType=</varname></term>
1179           <listitem>
1180             <para>Override the global <varname>DUIDType</varname> setting for this network. See
1181             <citerefentry><refentrytitle>networkd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1182             for a description of possible values.</para>
1183           </listitem>
1184         </varlistentry>
1185
1186         <varlistentry>
1187           <term><varname>DUIDRawData=</varname></term>
1188           <listitem>
1189             <para>Override the global <varname>DUIDRawData</varname> setting for this network. See
1190             <citerefentry><refentrytitle>networkd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1191             for a description of possible values.</para>
1192           </listitem>
1193         </varlistentry>
1194
1195         <varlistentry>
1196           <term><varname>IAID=</varname></term>
1197           <listitem>
1198             <para>The DHCP Identity Association Identifier (IAID) for the interface, a 32-bit unsigned integer.</para>
1199           </listitem>
1200         </varlistentry>
1201
1202         <varlistentry>
1203           <term><varname>RequestBroadcast=</varname></term>
1204           <listitem>
1205             <para>Request the server to use broadcast messages before
1206             the IP address has been configured. This is necessary for
1207             devices that cannot receive RAW packets, or that cannot
1208             receive packets at all before an IP address has been
1209             configured. On the other hand, this must not be enabled on
1210             networks where broadcasts are filtered out.</para>
1211           </listitem>
1212         </varlistentry>
1213
1214         <varlistentry>
1215           <term><varname>RouteMetric=</varname></term>
1216           <listitem>
1217             <para>Set the routing metric for routes specified by the
1218             DHCP server.</para>
1219           </listitem>
1220         </varlistentry>
1221
1222         <varlistentry>
1223           <term><varname>RouteTable=<replaceable>num</replaceable></varname></term>
1224           <listitem>
1225             <para>The table identifier for DHCP routes (a number between 1 and 4294967295, or 0 to unset).
1226             The table can be retrieved using <command>ip route show table <replaceable>num</replaceable></command>.
1227             </para>
1228             <para>When used in combination with <varname>VRF=</varname> the
1229             VRF's routing table is used unless this parameter is specified.
1230             </para>
1231           </listitem>
1232         </varlistentry>
1233
1234         <varlistentry>
1235           <term><varname>ListenPort=</varname></term>
1236           <listitem>
1237             <para>Allow setting custom port for the DHCP client to listen on.</para>
1238           </listitem>
1239         </varlistentry>
1240       </variablelist>
1241     </refsect1>
1242
1243   <refsect1>
1244     <title>[IPv6AcceptRA] Section Options</title>
1245       <para>The <literal>[IPv6AcceptRA]</literal> section configures the IPv6 Router Advertisement
1246       (RA) client, if it is enabled with the <varname>IPv6AcceptRA=</varname> setting described
1247       above:</para>
1248
1249       <variablelist class='network-directives'>
1250         <varlistentry>
1251           <term><varname>UseDNS=</varname></term>
1252           <listitem>
1253             <para>When true (the default), the DNS servers received in the Router Advertisement will be used and take
1254             precedence over any statically configured ones.</para>
1255
1256             <para>This corresponds to the <option>nameserver</option> option in <citerefentry
1257             project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
1258           </listitem>
1259         </varlistentry>
1260
1261         <varlistentry>
1262           <term><varname>UseDomains=</varname></term>
1263           <listitem>
1264             <para>Takes a boolean argument, or the special value <literal>route</literal>. When true, the domain name
1265             received via IPv6 Router Advertisement (RA) will be used as DNS search domain over this link, similar to
1266             the effect of the <option>Domains=</option> setting. If set to <literal>route</literal>, the domain name
1267             received via IPv6 RA will be used for routing DNS queries only, but not for searching, similar to the
1268             effect of the <option>Domains=</option> setting when the argument is prefixed with
1269             <literal>~</literal>. Defaults to false.</para>
1270
1271             <para>It is recommended to enable this option only on trusted networks, as setting this affects resolution
1272             of all host names, in particular of single-label names. It is generally safer to use the supplied domain
1273             only as routing domain, rather than as search domain, in order to not have it affect local resolution of
1274             single-label names.</para>
1275
1276             <para>When set to true, this setting corresponds to the <option>domain</option> option in <citerefentry
1277             project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
1278           </listitem>
1279         </varlistentry>
1280
1281         <varlistentry>
1282           <term><varname>RouteTable=<replaceable>num</replaceable></varname></term>
1283           <listitem>
1284             <para>The table identifier for the routes received in the Router Advertisement
1285             (a number between 1 and 4294967295, or 0 to unset).
1286             The table can be retrieved using <command>ip route show table <replaceable>num</replaceable></command>.
1287             </para>
1288           </listitem>
1289         </varlistentry>
1290       </variablelist>
1291   </refsect1>
1292
1293
1294   <refsect1>
1295     <title>[DHCPServer] Section Options</title>
1296     <para>The <literal>[DHCPServer]</literal> section contains
1297     settings for the DHCP server, if enabled via the
1298     <varname>DHCPServer=</varname> option described above:</para>
1299
1300     <variablelist class='network-directives'>
1301
1302       <varlistentry>
1303         <term><varname>PoolOffset=</varname></term>
1304         <term><varname>PoolSize=</varname></term>
1305
1306         <listitem><para>Configures the pool of addresses to hand out. The pool
1307         is a contiguous sequence of IP addresses in the subnet configured for
1308         the server address, which does not include the subnet nor the broadcast
1309         address. <varname>PoolOffset=</varname> takes the offset of the pool
1310         from the start of subnet, or zero to use the default value.
1311         <varname>PoolSize=</varname> takes the number of IP addresses in the
1312         pool or zero to use the default value. By default, the pool starts at
1313         the first address after the subnet address and takes up the rest of
1314         the subnet, excluding the broadcast address. If the pool includes
1315         the server address (the default), this is reserved and not handed
1316         out to clients.</para></listitem>
1317       </varlistentry>
1318
1319       <varlistentry>
1320         <term><varname>DefaultLeaseTimeSec=</varname></term>
1321         <term><varname>MaxLeaseTimeSec=</varname></term>
1322
1323         <listitem><para>Control the default and maximum DHCP lease
1324         time to pass to clients. These settings take time values in seconds or
1325         another common time unit, depending on the suffix. The default
1326         lease time is used for clients that did not ask for a specific
1327         lease time. If a client asks for a lease time longer than the
1328         maximum lease time, it is automatically shortened to the
1329         specified time. The default lease time defaults to 1h, the
1330         maximum lease time to 12h. Shorter lease times are beneficial
1331         if the configuration data in DHCP leases changes frequently
1332         and clients shall learn the new settings with shorter
1333         latencies. Longer lease times reduce the generated DHCP
1334         network traffic.</para></listitem>
1335       </varlistentry>
1336
1337       <varlistentry>
1338         <term><varname>EmitDNS=</varname></term>
1339         <term><varname>DNS=</varname></term>
1340
1341         <listitem><para>Configures whether the DHCP leases handed out
1342         to clients shall contain DNS server information. The
1343         <varname>EmitDNS=</varname> setting takes a boolean argument
1344         and defaults to <literal>yes</literal>. The DNS servers to
1345         pass to clients may be configured with the
1346         <varname>DNS=</varname> option, which takes a list of IPv4
1347         addresses. If the <varname>EmitDNS=</varname> option is
1348         enabled but no servers configured, the servers are
1349         automatically propagated from an "uplink" interface that has
1350         appropriate servers set. The "uplink" interface is determined
1351         by the default route of the system with the highest
1352         priority. Note that this information is acquired at the time
1353         the lease is handed out, and does not take uplink interfaces
1354         into account that acquire DNS or NTP server information at a
1355         later point. DNS server propagation does not take
1356         <filename>/etc/resolv.conf</filename> into account. Also, note
1357         that the leases are not refreshed if the uplink network
1358         configuration changes. To ensure clients regularly acquire the
1359         most current uplink DNS server information, it is thus
1360         advisable to shorten the DHCP lease time via
1361         <varname>MaxLeaseTimeSec=</varname> described
1362         above.</para></listitem>
1363       </varlistentry>
1364
1365       <varlistentry>
1366         <term><varname>EmitNTP=</varname></term>
1367         <term><varname>NTP=</varname></term>
1368
1369         <listitem><para>Similar to the <varname>EmitDNS=</varname> and
1370         <varname>DNS=</varname> settings described above, these
1371         settings configure whether and what NTP server information
1372         shall be emitted as part of the DHCP lease. The same syntax,
1373         propagation semantics and defaults apply as for
1374         <varname>EmitDNS=</varname> and
1375         <varname>DNS=</varname>.</para></listitem>
1376       </varlistentry>
1377
1378       <varlistentry>
1379         <term><varname>EmitRouter=</varname></term>
1380
1381         <listitem><para>Similar to the <varname>EmitDNS=</varname>
1382         setting described above, this setting configures whether the
1383         DHCP lease should contain the router option. The same syntax,
1384         propagation semantics and defaults apply as for
1385         <varname>EmitDNS=</varname>.</para></listitem>
1386       </varlistentry>
1387
1388       <varlistentry>
1389         <term><varname>EmitTimezone=</varname></term>
1390         <term><varname>Timezone=</varname></term>
1391
1392         <listitem><para>Configures whether the DHCP leases handed out
1393         to clients shall contain timezone information. The
1394         <varname>EmitTimezone=</varname> setting takes a boolean
1395         argument and defaults to <literal>yes</literal>. The
1396         <varname>Timezone=</varname> setting takes a timezone string
1397         (such as <literal>Europe/Berlin</literal> or
1398         <literal>UTC</literal>) to pass to clients. If no explicit
1399         timezone is set, the system timezone of the local host is
1400         propagated, as determined by the
1401         <filename>/etc/localtime</filename> symlink.</para></listitem>
1402       </varlistentry>
1403
1404     </variablelist>
1405   </refsect1>
1406
1407   <refsect1>
1408     <title>[IPv6PrefixDelegation] Section Options</title>
1409     <para>The <literal>[IPv6PrefixDelegation]</literal> section contains
1410     settings for sending IPv6 Router Advertisements and whether to act as
1411     a router, if enabled via the <varname>IPv6PrefixDelegation=</varname>
1412     option described above. IPv6 network prefixes are defined with one or
1413     more <literal>[IPv6Prefix]</literal> sections.</para>
1414
1415     <variablelist class='network-directives'>
1416
1417       <varlistentry>
1418         <term><varname>Managed=</varname></term>
1419         <term><varname>OtherInformation=</varname></term>
1420
1421         <listitem><para>Controls whether a DHCPv6 server is used to acquire IPv6
1422         addresses on the network link when <varname>Managed=</varname> boolean
1423         is set to <literal>true</literal> or if only additional network
1424         information can be obtained via DHCPv6 for the network link when
1425         <varname>OtherInformation=</varname> boolean is set to
1426         <literal>true</literal>. Both settings default to
1427         <literal>false</literal>, which means that a DHCPv6 server is not being
1428         used.</para></listitem>
1429       </varlistentry>
1430
1431       <varlistentry>
1432         <term><varname>RouterLifetimeSec=</varname></term>
1433
1434         <listitem><para>Configures the IPv6 router lifetime in seconds. If set,
1435         this host also announces itself in Router Advertisements as an IPv6
1436         router for the network link. Defaults to unset, which means the host is
1437         not acting as a router.</para>
1438         </listitem>
1439       </varlistentry>
1440
1441       <varlistentry>
1442         <term><varname>RouterPreference=</varname></term>
1443
1444         <listitem><para>Configures IPv6 router preference if
1445         <varname>RouterLifetimeSec=</varname> is non-zero. Valid values are
1446         <literal>high</literal>, <literal>medium</literal> and
1447         <literal>low</literal>, with <literal>normal</literal> and
1448         <literal>default</literal> added as synonyms for
1449         <literal>medium</literal> just to make configuration easier. See
1450         <ulink url="https://tools.ietf.org/html/rfc4191">RFC 4191</ulink>
1451         for details. Defaults to <literal>medium</literal>.</para></listitem>
1452       </varlistentry>
1453
1454       <varlistentry>
1455         <term><varname>DNS=</varname></term>
1456
1457         <listitem><para>A list of recursive DNS server IPv6 addresses
1458         distributed via Router Advertisement messages.
1459         </para></listitem>
1460       </varlistentry>
1461
1462       <varlistentry>
1463         <term><varname>Domains=</varname></term>
1464
1465         <listitem><para>A list of DNS search domains distributed via
1466         Router Advertisement messages. Defaults to empty, i.e. no search
1467         domains are sent.</para></listitem>
1468       </varlistentry>
1469
1470       <varlistentry>
1471         <term><varname>DNSLifetimeSec=</varname></term>
1472
1473         <listitem><para>Lifetime in seconds for the DNS server addresses listed
1474         in <varname>DNS=</varname> and search domains listed in
1475         <varname>Domains=</varname>.</para></listitem>
1476       </varlistentry>
1477
1478     </variablelist>
1479     </refsect1>
1480
1481       <refsect1>
1482     <title>[IPv6Prefix] Section Options</title>
1483     <para>One or more <literal>[IPv6Prefix]</literal> sections contain the IPv6
1484     prefixes that are announced via Router Advertisements. See
1485     <ulink url="https://tools.ietf.org/html/rfc4861">RFC 4861</ulink>
1486     for further details.</para>
1487
1488     <variablelist class='network-directives'>
1489
1490       <varlistentry>
1491         <term><varname>AddressAutoconfiguration=</varname></term>
1492         <term><varname>OnLink=</varname></term>
1493
1494         <listitem><para>Boolean values to specify whether IPv6 addresses can be
1495         autoconfigured with this prefix and whether the prefix can be used for
1496         onlink determination. Both settings default to <literal>true</literal>
1497         in order to ease configuration.
1498         </para></listitem>
1499       </varlistentry>
1500
1501       <varlistentry>
1502         <term><varname>Prefix=</varname></term>
1503
1504         <listitem><para>The IPv6 prefix that is to be distributed to hosts.
1505         Similarly to configuring static IPv6 addresses, the setting is
1506         configured as an IPv6 prefix and its prefix length, separated by a
1507         <literal>/</literal> character. Use multiple
1508         <literal>[IPv6Prefix]</literal> sections to configure multiple IPv6
1509         prefixes since prefix lifetimes, address autoconfiguration and onlink
1510         status may differ from one prefix to another.</para></listitem>
1511       </varlistentry>
1512
1513       <varlistentry>
1514         <term><varname>PreferredLifetimeSec=</varname></term>
1515         <term><varname>ValidLifetimeSec=</varname></term>
1516
1517         <listitem><para>Preferred and valid lifetimes for the prefix measured in
1518         seconds. <varname>PreferredLifetimeSec=</varname> defaults to 604800
1519         seconds (one week) and <varname>ValidLifetimeSec=</varname> defaults
1520         to 2592000 seconds (30 days).</para></listitem>
1521       </varlistentry>
1522
1523     </variablelist>
1524     </refsect1>
1525
1526     <refsect1>
1527     <title>[Bridge] Section Options</title>
1528       <para>The <literal>[Bridge]</literal> section accepts the
1529       following keys.</para>
1530       <variablelist class='network-directives'>
1531         <varlistentry>
1532           <term><varname>UnicastFlood=</varname></term>
1533           <listitem>
1534             <para>A boolean. Controls whether the bridge should flood
1535             traffic for which an FDB entry is missing and the destination
1536             is unknown through this port. Defaults to on.
1537             </para>
1538           </listitem>
1539         </varlistentry>
1540         <varlistentry>
1541           <term><varname>HairPin=</varname></term>
1542           <listitem>
1543             <para>A boolean. Configures whether traffic may be sent back
1544             out of the port on which it was received. By default, this
1545             flag is false, and the bridge will not forward traffic back
1546             out of the receiving port.</para>
1547           </listitem>
1548         </varlistentry>
1549         <varlistentry>
1550           <term><varname>UseBPDU=</varname></term>
1551           <listitem>
1552             <para>A boolean. Configures whether STP Bridge Protocol Data Units will be
1553             processed by the bridge port. Defaults to yes.</para>
1554           </listitem>
1555         </varlistentry>
1556         <varlistentry>
1557           <term><varname>FastLeave=</varname></term>
1558           <listitem>
1559             <para>A boolean. This flag allows the bridge to immediately stop multicast
1560             traffic on a port that receives an IGMP Leave message. It is only used with
1561             IGMP snooping if enabled on the bridge. Defaults to off.</para>
1562           </listitem>
1563         </varlistentry>
1564         <varlistentry>
1565           <term><varname>AllowPortToBeRoot=</varname></term>
1566           <listitem>
1567             <para>A boolean. Configures whether a given port is allowed to
1568             become a root port. Only used when STP is enabled on the bridge.
1569             Defaults to on.</para>
1570           </listitem>
1571         </varlistentry>
1572         <varlistentry>
1573           <term><varname>Cost=</varname></term>
1574           <listitem>
1575             <para>Sets the "cost" of sending packets of this interface.
1576             Each port in a bridge may have a different speed and the cost
1577             is used to decide which link to use. Faster interfaces
1578             should have lower costs. It is an integer value between 1 and
1579             65535.</para>
1580           </listitem>
1581         </varlistentry>
1582         <varlistentry>
1583           <term><varname>Priority=</varname></term>
1584           <listitem>
1585             <para>Sets the "priority" of sending packets on this interface.
1586             Each port in a bridge may have a different priority which is used
1587             to decide which link to use. Lower value means higher priority.
1588             It is an integer value between 0 to 63. Networkd does not set any
1589             default, meaning the kernel default value of 32 is used.</para>
1590           </listitem>
1591         </varlistentry>
1592       </variablelist>
1593   </refsect1>
1594   <refsect1>
1595     <title>[BridgeFDB] Section Options</title>
1596       <para>The <literal>[BridgeFDB]</literal> section manages the
1597       forwarding database table of a port and accepts the following
1598       keys. Specify several <literal>[BridgeFDB]</literal> sections to
1599       configure several static MAC table entries.</para>
1600
1601       <variablelist class='network-directives'>
1602         <varlistentry>
1603           <term><varname>MACAddress=</varname></term>
1604           <listitem>
1605             <para>As in the <literal>[Network]</literal> section. This
1606             key is mandatory.</para>
1607           </listitem>
1608         </varlistentry>
1609         <varlistentry>
1610           <term><varname>VLANId=</varname></term>
1611           <listitem>
1612             <para>The VLAN ID for the new static MAC table entry. If
1613             omitted, no VLAN ID info is appended to the new static MAC
1614             table entry.</para>
1615           </listitem>
1616         </varlistentry>
1617       </variablelist>
1618   </refsect1>
1619   <refsect1>
1620     <title>[BridgeVLAN] Section Options</title>
1621       <para>The <literal>[BridgeVLAN]</literal> section manages the VLAN ID configuration of a bridge port and accepts
1622       the following keys. Specify several <literal>[BridgeVLAN]</literal> sections to configure several VLAN entries.
1623       The <varname>VLANFiltering=</varname> option has to be enabled, see <literal>[Bridge]</literal> section in
1624       <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
1625
1626       <variablelist class='network-directives'>
1627         <varlistentry>
1628           <term><varname>VLAN=</varname></term>
1629           <listitem>
1630             <para>The VLAN ID allowed on the port. This can be either a single ID or a range M-N. VLAN IDs are valid
1631             from 1 to 4094.</para>
1632           </listitem>
1633         </varlistentry>
1634         <varlistentry>
1635           <term><varname>EgressUntagged=</varname></term>
1636           <listitem>
1637             <para>The VLAN ID specified here will be used to untag frames on egress. Configuring
1638             <varname>EgressUntagged=</varname> implicates the use of <varname>VLAN=</varname> above and will enable the
1639             VLAN ID for ingress as well. This can be either a single ID or a range M-N.</para>
1640           </listitem>
1641         </varlistentry>
1642         <varlistentry>
1643           <term><varname>PVID=</varname></term>
1644           <listitem>
1645             <para>The Port VLAN ID specified here is assigned to all untagged frames at ingress.
1646             <varname>PVID=</varname> can be used only once. Configuring <varname>PVID=</varname> implicates the use of
1647             <varname>VLAN=</varname> above and will enable the VLAN ID for ingress as well.</para>
1648           </listitem>
1649         </varlistentry>
1650       </variablelist>
1651   </refsect1>
1652
1653   <refsect1>
1654     <title>Examples</title>
1655     <example>
1656       <title>Static network configuration</title>
1657
1658       <programlisting># /etc/systemd/network/50-static.network
1659 [Match]
1660 Name=enp2s0
1661
1662 [Network]
1663 Address=192.168.0.15/24
1664 Gateway=192.168.0.1</programlisting>
1665
1666       <para>This brings interface <literal>enp2s0</literal> up with a static address. The
1667       specified gateway will be used for a default route.</para>
1668     </example>
1669
1670     <example>
1671       <title>DHCP on ethernet links</title>
1672
1673       <programlisting># /etc/systemd/network/80-dhcp.network
1674 [Match]
1675 Name=en*
1676
1677 [Network]
1678 DHCP=yes</programlisting>
1679
1680       <para>This will enable DHCPv4 and DHCPv6 on all interfaces with names starting with
1681       <literal>en</literal> (i.e. ethernet interfaces).</para>
1682     </example>
1683
1684     <example>
1685       <title>A bridge with two enslaved links</title>
1686
1687       <programlisting># /etc/systemd/network/25-bridge-static.network
1688 [Match]
1689 Name=bridge0
1690
1691 [Network]
1692 Address=192.168.0.15/24
1693 Gateway=192.168.0.1
1694 DNS=192.168.0.1</programlisting>
1695
1696       <programlisting># /etc/systemd/network/25-bridge-slave-interface-1.network
1697 [Match]
1698 Name=enp2s0
1699
1700 [Network]
1701 Bridge=bridge0</programlisting>
1702
1703       <programlisting># /etc/systemd/network/25-bridge-slave-interface-2.network
1704 [Match]
1705 Name=wlp3s0
1706
1707 [Network]
1708 Bridge=bridge0</programlisting>
1709
1710       <para>This creates a bridge and attaches devices <literal>enp2s0</literal> and
1711       <literal>wlp3s0</literal> to it. The bridge will have the specified static address
1712       and network assigned, and a default route via the specified gateway will be
1713       added. The specified DNS server will be added to the global list of DNS resolvers.
1714       </para>
1715     </example>
1716
1717     <example>
1718       <title></title>
1719
1720       <programlisting>
1721 # /etc/systemd/network/20-bridge-slave-interface-vlan.network
1722 [Match]
1723 Name=enp2s0
1724
1725 [Network]
1726 Bridge=bridge0
1727
1728 [BridgeVLAN]
1729 VLAN=1-32
1730 PVID=42
1731 EgressUntagged=42
1732
1733 [BridgeVLAN]
1734 VLAN=100-200
1735
1736 [BridgeVLAN]
1737 EgressUntagged=300-400</programlisting>
1738
1739     <para>This overrides the configuration specified in the previous example for the
1740     interface <literal>enp2s0</literal>, and enables VLAN on that bridge port. VLAN IDs
1741     1-32, 42, 100-400 will be allowed. Packets tagged with VLAN IDs 42, 300-400 will be
1742     untagged when they leave on this interface. Untagged packets which arrive on this
1743     interface will be assigned VLAN ID 42.</para>
1744     </example>
1745
1746     <example>
1747       <title>Various tunnels</title>
1748
1749       <programlisting>/etc/systemd/network/25-tunnels.network
1750 [Match]
1751 Name=ens1
1752
1753 [Network]
1754 Tunnel=ipip-tun
1755 Tunnel=sit-tun
1756 Tunnel=gre-tun
1757 Tunnel=vti-tun
1758       </programlisting>
1759
1760       <programlisting>/etc/systemd/network/25-tunnel-ipip.netdev
1761 [NetDev]
1762 Name=ipip-tun
1763 Kind=ipip
1764       </programlisting>
1765
1766       <programlisting>/etc/systemd/network/25-tunnel-sit.netdev
1767 [NetDev]
1768 Name=sit-tun
1769 Kind=sit
1770       </programlisting>
1771
1772       <programlisting>/etc/systemd/network/25-tunnel-gre.netdev
1773 [NetDev]
1774 Name=gre-tun
1775 Kind=gre
1776       </programlisting>
1777
1778       <programlisting>/etc/systemd/network/25-tunnel-vti.netdev
1779 [NetDev]
1780 Name=vti-tun
1781 Kind=vti
1782       </programlisting>
1783
1784       <para>This will bring interface <literal>ens1</literal> up and create an IPIP tunnel,
1785       a SIT tunnel, a GRE tunnel, and a VTI tunnel using it.</para>
1786     </example>
1787
1788     <example>
1789       <title>A bond device</title>
1790
1791       <programlisting># /etc/systemd/network/30-bond1.network
1792 [Match]
1793 Name=bond1
1794
1795 [Network]
1796 DHCP=ipv6
1797 </programlisting>
1798
1799       <programlisting># /etc/systemd/network/30-bond1.netdev
1800 [NetDev]
1801 Name=bond1
1802 Kind=bond
1803 </programlisting>
1804
1805       <programlisting># /etc/systemd/network/30-bond1-dev1.network
1806 [Match]
1807 MACAddress=52:54:00:e9:64:41
1808
1809 [Network]
1810 Bond=bond1
1811 </programlisting>
1812
1813       <programlisting># /etc/systemd/network/30-bond1-dev2.network
1814 [Match]
1815 MACAddress=52:54:00:e9:64:42
1816
1817 [Network]
1818 Bond=bond1
1819 </programlisting>
1820
1821     <para>This will create a bond device <literal>bond1</literal> and enslave the two
1822     devices with MAC addresses 52:54:00:e9:64:41 and 52:54:00:e9:64:42 to it. IPv6 DHCP
1823     will be used to acquire an address.</para>
1824     </example>
1825
1826     <example>
1827       <title>Virtual Routing and Forwarding (VRF)</title>
1828       <para>Add the <literal>bond1</literal> interface to the VRF master interface
1829       <literal>vrf1</literal>. This will redirect routes generated on this interface to be
1830       within the routing table defined during VRF creation. For kernels before 4.8 traffic
1831       won't be redirected towards the VRFs routing table unless specific ip-rules are added.
1832       </para>
1833       <programlisting># /etc/systemd/network/25-vrf.network
1834 [Match]
1835 Name=bond1
1836
1837 [Network]
1838 VRF=vrf1
1839 </programlisting>
1840     </example>
1841
1842     <example>
1843       <title>MacVTap</title>
1844       <para>This brings up a network interface <literal>macvtap-test</literal>
1845       and attaches it to <literal>enp0s25</literal>.</para>
1846       <programlisting># /usr/lib/systemd/network/25-macvtap.network
1847 [Match]
1848 Name=enp0s25
1849
1850 [Network]
1851 MACVTAP=macvtap-test
1852 </programlisting>
1853     </example>
1854   </refsect1>
1855
1856   <refsect1>
1857     <title>See Also</title>
1858     <para>
1859       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1860       <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1861       <citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1862       <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1863       <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
1864     </para>
1865   </refsect1>
1866
1867 </refentry>