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>Network files must have the extension
  62     <filename>.network</filename>; other extensions are ignored.
  63     Networks are applied to links whenever the links appear.</para>
  64
  65     <para>The <filename>.network</filename> files are read from the
  66     files located in the system network directory
  67     <filename>/usr/lib/systemd/network</filename>, the volatile
  68     runtime network directory
  69     <filename>/run/systemd/network</filename> and the local
  70     administration network directory
  71     <filename>/etc/systemd/network</filename>. All configuration files
  72     are collectively sorted and processed in lexical order, regardless
  73     of the directories in which they live. However, files with
  74     identical filenames replace each other. Files in
  75     <filename>/etc</filename> have the highest priority, files in
  76     <filename>/run</filename> take precedence over files with the same
  77     name in <filename>/usr/lib</filename>. This can be used to
  78     override a system-supplied configuration file with a local file if
  79     needed; a symlink in <filename>/etc</filename> with the same name
  80     as a configuration file in <filename>/usr/lib</filename>, pointing
  81     to <filename>/dev/null</filename>, disables the configuration file
  82     entirely.</para>
  83
  84   </refsect1>
  85
  86   <refsect1>
  87     <title>[Match] Section Options</title>
  88
  89       <para>The network file contains a <literal>[Match]</literal>
  90       section, which determines if a given network file may be applied
  91       to a given device; and a <literal>[Network]</literal> section
  92       specifying how the device should be configured. The first (in
  93       lexical order) of the network files that matches a given device
  94       is applied, all later files are ignored, even if they match as
  95       well.</para>
  96
  97       <para>A network file is said to match a device if each of the
  98       entries in the <literal>[Match]</literal> section matches, or if
  99       the section is empty. The following keys are accepted:</para>
 100
 101       <variablelist class='network-directives'>
 102         <varlistentry>
 103           <term><varname>MACAddress=</varname></term>
 104           <listitem>
 105             <para>The hardware address.</para>
 106           </listitem>
 107         </varlistentry>
 108         <varlistentry>
 109           <term><varname>Path=</varname></term>
 110           <listitem>
 111             <para>A whitespace-separated list of shell-style globs
 112             matching the persistent path, as exposed by the udev
 113             property <literal>ID_PATH</literal>.</para>
 114           </listitem>
 115         </varlistentry>
 116         <varlistentry>
 117           <term><varname>Driver=</varname></term>
 118           <listitem>
 119             <para>A whitespace-separated list of shell-style globs
 120             matching the driver currently bound to the device, as
 121             exposed by the udev property <literal>DRIVER</literal>
 122             of its parent device, or if that is not set the driver
 123             as exposed by <literal>ethtool -i</literal> of the
 124             device itself.</para>
 125           </listitem>
 126         </varlistentry>
 127         <varlistentry>
 128           <term><varname>Type=</varname></term>
 129           <listitem>
 130             <para>A whitespace-separated list of shell-style globs
 131             matching the device type, as exposed by the udev property
 132             <literal>DEVTYPE</literal>.</para>
 133           </listitem>
 134         </varlistentry>
 135         <varlistentry>
 136           <term><varname>Name=</varname></term>
 137           <listitem>
 138             <para>A whitespace-separated list of shell-style globs
 139             matching the device name, as exposed by the udev property
 140             <literal>INTERFACE</literal>.</para>
 141           </listitem>
 142         </varlistentry>
 143         <varlistentry>
 144           <term><varname>Host=</varname></term>
 145           <listitem>
 146             <para>Matches against the hostname or machine ID of the
 147             host. See <literal>ConditionHost=</literal> in
 148             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 149             for details.
 150             </para>
 151           </listitem>
 152         </varlistentry>
 153         <varlistentry>
 154           <term><varname>Virtualization=</varname></term>
 155           <listitem>
 156             <para>Checks whether the system is executed in a virtualized
 157             environment and optionally test whether it is a specific
 158             implementation. See <literal>ConditionVirtualization=</literal> in
 159             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 160             for details.
 161             </para>
 162           </listitem>
 163         </varlistentry>
 164         <varlistentry>
 165           <term><varname>KernelCommandLine=</varname></term>
 166           <listitem>
 167             <para>Checks whether a specific kernel command line option is
 168             set (or if prefixed with the exclamation mark unset). See
 169             <literal>ConditionKernelCommandLine=</literal> in
 170             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 171             for details.
 172             </para>
 173           </listitem>
 174         </varlistentry>
 175         <varlistentry>
 176           <term><varname>Architecture=</varname></term>
 177           <listitem>
 178             <para>Checks whether the system is running on a specific
 179             architecture. See <literal>ConditionArchitecture=</literal> in
 180             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 181             for details.
 182             </para>
 183           </listitem>
 184         </varlistentry>
 185       </variablelist>
 186
 187   </refsect1>
 188
 189   <refsect1>
 190     <title>[Link] Section Options</title>
 191
 192     <para> The <literal>[Link]</literal> section accepts the following keys:</para>
 193
 194     <variablelist class='network-directives'>
 195       <varlistentry>
 196         <term><varname>MACAddress=</varname></term>
 197         <listitem>
 198           <para>The hardware address.</para>
 199         </listitem>
 200       </varlistentry>
 201       <varlistentry>
 202         <term><varname>MTUBytes=</varname></term>
 203         <listitem>
 204           <para>The maximum transmission unit in bytes to set for the
 205           device. The usual suffixes K, M, G, are supported and are
 206           understood to the base of 1024.</para>
 207         </listitem>
 208       </varlistentry>
 209     </variablelist>
 210   </refsect1>
 211
 212   <refsect1>
 213     <title>[Network] Section Options</title>
 214
 215       <para>The <literal>[Network]</literal> section accepts the following keys:</para>
 216
 217       <variablelist class='network-directives'>
 218         <varlistentry>
 219           <term><varname>Description=</varname></term>
 220           <listitem>
 221             <para>A description of the device. This is only used for
 222             presentation purposes.</para>
 223           </listitem>
 224         </varlistentry>
 225         <varlistentry>
 226           <term><varname>DHCP=</varname></term>
 227           <listitem>
 228             <para>Enables DHCPv4 and/or DHCPv6 support. Accepts
 229             <literal>yes</literal>, <literal>no</literal>,
 230             <literal>ipv4</literal>, or <literal>ipv6</literal>.</para>
 231
 232             <para>Please note that by default the domain name
 233             specified through DHCP is not used for name resolution.
 234             See option <option>UseDomains=</option> below.</para>
 235           </listitem>
 236         </varlistentry>
 237         <varlistentry>
 238           <term><varname>DHCPServer=</varname></term>
 239           <listitem>
 240             <para>A boolean. Enables a basic DHCPv4 server on the
 241             device. Mostly useful for handing out leases to container
 242             instances.</para>
 243           </listitem>
 244         </varlistentry>
 245         <varlistentry>
 246           <term><varname>LinkLocalAddressing=</varname></term>
 247           <listitem>
 248             <para>Enables link-local address autoconfiguration. Accepts
 249             <literal>yes</literal>, <literal>no</literal>,
 250             <literal>ipv4</literal>, or <literal>ipv6</literal>. Defaults to
 251             <literal>ipv6</literal>.</para>
 252           </listitem>
 253         </varlistentry>
 254         <varlistentry>
 255           <term><varname>IPv4LLRoute=</varname></term>
 256           <listitem>
 257             <para>A boolean. When true, sets up the route needed for
 258             non-IPv4LL hosts to communicate with IPv4LL-only hosts. Defaults
 259             to false.
 260             </para>
 261           </listitem>
 262         </varlistentry>
 263         <varlistentry>
 264           <term><varname>IPv6Token=</varname></term>
 265           <listitem>
 266             <para>An IPv6 address with the top 64 bits unset. When set, indicates the
 267             64 bits interface part of SLAAC IPv6 addresses for this link. By default
 268             it is autogenerated.</para>
 269           </listitem>
 270         </varlistentry>
 271         <varlistentry>
 272           <term><varname>LLMNR=</varname></term>
 273           <listitem>
 274             <para>A boolean or <literal>resolve</literal>. When true, enables
 275             Link-Local Multicast Name Resolution on the link, when set to
 276             <literal>resolve</literal> only resolution is enabled, but not
 277             announcement. Defaults to true.</para>
 278           </listitem>
 279         </varlistentry>
 280         <varlistentry>
 281           <term><varname>LLDP=</varname></term>
 282           <listitem>
 283             <para>A boolean. When true, enables LLDP link receive support.
 284             </para>
 285           </listitem>
 286         </varlistentry>
 287         <varlistentry>
 288           <term><varname>BindCarrier=</varname></term>
 289           <listitem>
 290             <para>A port or a list of ports. When set, controls the
 291             behaviour of the current interface. When all ports in the list
 292             are in an operational down state, the current interface is brought
 293             down. When at least one port has carrier, the current interface
 294             is brought up.
 295             </para>
 296           </listitem>
 297         </varlistentry>
 298         <varlistentry>
 299           <term><varname>Address=</varname></term>
 300           <listitem>
 301             <para>A static IPv4 or IPv6 address and its prefix length,
 302             separated by a <literal>/</literal> character. Specify
 303             this key more than once to configure several addresses.
 304             The format of the address must be as described in
 305             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 306             This is a short-hand for an [Address] section only
 307             containing an Address key (see below). This option may be
 308             specified more than once.
 309             </para>
 310
 311             <para>If the specified address is 0.0.0.0 (for IPv4) or
 312             [::] (for IPv6), a new address range of the requested size
 313             is automatically allocated from a system-wide pool of
 314             unused ranges. The allocated range is checked against all
 315             current network interfaces and all known network
 316             configuration files to avoid address range conflicts. The
 317             default system-wide pool consists of 192.168.0.0/16,
 318             172.16.0.0/12 and 10.0.0.0/8 for IPv4, and fc00::/7 for
 319             IPv6. This functionality is useful to manage a large
 320             number of dynamically created network interfaces with the
 321             same network configuration and automatic address range
 322             assignment.</para>
 323
 324           </listitem>
 325         </varlistentry>
 326         <varlistentry>
 327           <term><varname>Gateway=</varname></term>
 328           <listitem>
 329             <para>The gateway address, which must be in the format
 330             described in
 331             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 332             This is a short-hand for a [Route] section only containing
 333             a Gateway key. This option may be specified more than
 334             once.</para>
 335           </listitem>
 336         </varlistentry>
 337         <varlistentry>
 338           <term><varname>DNS=</varname></term>
 339           <listitem>
 340             <para>A DNS server address, which must be in the format
 341             described in
 342             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 343             This option may be specified more than once.</para>
 344           </listitem>
 345         </varlistentry>
 346         <varlistentry>
 347           <term><varname>Domains=</varname></term>
 348           <listitem>
 349             <para>The domains used for DNS resolution over this link.</para>
 350           </listitem>
 351         </varlistentry>
 352         <varlistentry>
 353           <term><varname>NTP=</varname></term>
 354           <listitem>
 355             <para>An NTP server address. This option may be specified more than once.</para>
 356           </listitem>
 357         </varlistentry>
 358         <varlistentry>
 359           <term><varname>IPForward=</varname></term>
 360           <listitem><para>Configures IP forwarding for the network
 361           interface. If enabled incoming packets on the network
 362           interface will be forwarded to other interfaces according to
 363           the routing table. Takes either a boolean argument, or the
 364           values <literal>ipv4</literal> or <literal>ipv6</literal>,
 365           which only enables IP forwarding for the specified address
 366           family, or <literal>kernel</literal>, which preserves existing sysctl settings.
 367           This controls the
 368           <filename>net.ipv4.conf.&lt;interface&gt;.forwarding</filename>
 369           and
 370           <filename>net.ipv6.conf.&lt;interface&gt;.forwarding</filename>
 371           sysctl options of the network interface (see <ulink
 372           url="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">ip-sysctl.txt</ulink>
 373           for details about sysctl options). Defaults to
 374           <literal>no</literal>.</para>
 375
 376          <para>Note: unless this option is turned on, or set to <literal>kernel</literal>,
 377           no IP forwarding is done on this interface, even if this is
 378           globally turned on in the kernel, with the
 379           <filename>net.ipv4.ip_forward</filename>,
 380           <filename>net.ipv4.conf.all.forwarding</filename>, and
 381           <filename>net.ipv6.conf.all.forwarding</filename> sysctl
 382           options.</para>
 383           </listitem>
 384         </varlistentry>
 385         <varlistentry>
 386           <term><varname>IPMasquerade=</varname></term>
 387           <listitem><para>Configures IP masquerading for the network
 388           interface. If enabled packets forwarded from the network
 389           interface will be appear as coming from the local host.
 390           Takes a boolean argument. Implies
 391           <varname>IPForward=ipv4</varname>. Defaults to
 392           <literal>no</literal>.</para></listitem>
 393         </varlistentry>
 394         <varlistentry>
 395           <term><varname>IPv6PrivacyExtensions=</varname></term>
 396           <listitem><para>Configures use of stateless temporary
 397           addresses that change over time (see <ulink
 398           url="https://tools.ietf.org/html/rfc4941">RFC 4941</ulink>,
 399           Privacy Extensions for Stateless Address Autoconfiguration
 400           in IPv6). Takes a boolean or the special values
 401           <literal>prefer-public</literal> and
 402           <literal>kernel</literal>. When true enables the privacy
 403           extensions and prefers temporary addresses over public
 404           addresses. When <literal>prefer-public</literal> enables the
 405           privacy extensions, but prefers public addresses over
 406           temporary addresses. When false, the privacy extensions
 407           remain disabled. When <literal>kernel</literal> the kernel's
 408           default setting will be left in place.  Defaults to
 409           <literal>no</literal>.</para></listitem>
 410         </varlistentry>
 411         <varlistentry>
 412           <term><varname>Bridge=</varname></term>
 413           <listitem>
 414             <para>The name of the bridge to add the link to.</para>
 415           </listitem>
 416         </varlistentry>
 417         <varlistentry>
 418           <term><varname>Bond=</varname></term>
 419           <listitem>
 420             <para>The name of the bond to add the link to.</para>
 421           </listitem>
 422         </varlistentry>
 423         <varlistentry>
 424           <term><varname>VLAN=</varname></term>
 425           <listitem>
 426             <para>The name of a VLAN to create on the link. This
 427             option may be specified more than once.</para>
 428           </listitem>
 429         </varlistentry>
 430         <varlistentry>
 431           <term><varname>MACVLAN=</varname></term>
 432           <listitem>
 433             <para>The name of a MACVLAN to create on the link. This
 434             option may be specified more than once.</para>
 435           </listitem>
 436         </varlistentry>
 437         <varlistentry>
 438           <term><varname>VXLAN=</varname></term>
 439           <listitem>
 440             <para>The name of a VXLAN to create on the link. This
 441             option may be specified more than once.</para>
 442           </listitem>
 443         </varlistentry>
 444         <varlistentry>
 445           <term><varname>Tunnel=</varname></term>
 446           <listitem>
 447             <para>The name of a Tunnel to create on the link. This
 448             option may be specified more than once.</para>
 449           </listitem>
 450         </varlistentry>
 451       </variablelist>
 452
 453   </refsect1>
 454
 455   <refsect1>
 456     <title>[Address] Section Options</title>
 457
 458       <para>An <literal>[Address]</literal> section accepts the
 459       following keys. Specify several <literal>[Address]</literal>
 460       sections to configure several addresses.</para>
 461
 462       <variablelist class='network-directives'>
 463         <varlistentry>
 464           <term><varname>Address=</varname></term>
 465           <listitem>
 466             <para>As in the <literal>[Network]</literal> section. This
 467             key is mandatory.</para>
 468           </listitem>
 469         </varlistentry>
 470         <varlistentry>
 471           <term><varname>Peer=</varname></term>
 472           <listitem>
 473             <para>The peer address in a point-to-point connection.
 474             Accepts the same format as the <literal>Address</literal>
 475             key.</para>
 476           </listitem>
 477         </varlistentry>
 478         <varlistentry>
 479           <term><varname>Broadcast=</varname></term>
 480           <listitem>
 481             <para>The broadcast address, which must be in the format
 482             described in
 483             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 484             This key only applies to IPv4 addresses. If it is not
 485             given, it is derived from the <literal>Address</literal>
 486             key.</para>
 487           </listitem>
 488         </varlistentry>
 489         <varlistentry>
 490           <term><varname>Label=</varname></term>
 491           <listitem>
 492             <para>An address label.</para>
 493           </listitem>
 494         </varlistentry>
 495       </variablelist>
 496   </refsect1>
 497
 498   <refsect1>
 499     <title>[Route] Section Options</title>
 500       <para>The <literal>[Route]</literal> section accepts the
 501       following keys. Specify several <literal>[Route]</literal>
 502       sections to configure several routes.</para>
 503
 504       <variablelist class='network-directives'>
 505         <varlistentry>
 506           <term><varname>Gateway=</varname></term>
 507           <listitem>
 508             <para>As in the <literal>[Network]</literal> section.</para>
 509           </listitem>
 510         </varlistentry>
 511         <varlistentry>
 512           <term><varname>Destination=</varname></term>
 513           <listitem>
 514             <para>The destination prefix of the route. Possibly
 515             followed by a slash and the prefixlength. If omitted, a
 516             full-length host route is assumed.</para>
 517           </listitem>
 518         </varlistentry>
 519         <varlistentry>
 520           <term><varname>Source=</varname></term>
 521           <listitem>
 522             <para>The source prefix of the route. Possibly followed by
 523             a slash and the prefixlength. If omitted, a full-length
 524             host route is assumed.</para>
 525           </listitem>
 526         </varlistentry>
 527         <varlistentry>
 528           <term><varname>Metric=</varname></term>
 529           <listitem>
 530             <para>The metric of the route. An unsigned integer</para>
 531           </listitem>
 532         </varlistentry>
 533         <varlistentry>
 534           <term><varname>Scope=</varname></term>
 535           <listitem>
 536             <para>The scope of the route. One of the values <literal>global</literal>,
 537             <literal>link</literal> or <literal>host</literal>. Defaults to
 538             <literal>global</literal>.</para>
 539           </listitem>
 540         </varlistentry>
 541       </variablelist>
 542   </refsect1>
 543
 544   <refsect1>
 545     <title>[DHCP] Section Options</title>
 546       <para>The <literal>[DHCP]</literal> section accepts the following keys:</para>
 547
 548       <variablelist class='network-directives'>
 549         <varlistentry>
 550           <term><varname>UseDNS=</varname></term>
 551           <listitem>
 552             <para>When true (the default), the DNS servers received
 553             from the DHCP server will be used and take precedence over
 554             any statically configured ones.</para>
 555
 556             <para>This corresponds to the <option>nameserver</option>
 557             option in <citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 558           </listitem>
 559         </varlistentry>
 560         <varlistentry>
 561           <term><varname>UseNTP=</varname></term>
 562           <listitem>
 563             <para>When true (the default), the NTP servers received
 564             from the DHCP server will be used by systemd-timesyncd
 565             and take precedence over any statically configured ones.</para>
 566           </listitem>
 567         </varlistentry>
 568         <varlistentry>
 569           <term><varname>UseMTU=</varname></term>
 570           <listitem>
 571             <para>When true, the interface maximum transmission unit
 572             from the DHCP server will be used on the current link.
 573             Defaults to false.</para>
 574           </listitem>
 575         </varlistentry>
 576         <varlistentry>
 577           <term><varname>SendHostname=</varname></term>
 578           <listitem>
 579             <para>When true (the default), the machine's hostname will be sent to the DHCP
 580             server</para>
 581           </listitem>
 582         </varlistentry>
 583         <varlistentry>
 584           <term><varname>UseHostname=</varname></term>
 585           <listitem>
 586             <para>When true (the default), the hostname received from
 587             the DHCP server will be used as the transient
 588             hostname.</para>
 589           </listitem>
 590         </varlistentry>
 591         <varlistentry>
 592         <term><varname>Hostname=</varname></term>
 593         <listitem>
 594           <para>Hostname is a option to override the machine's hostname that will be sent to the DHCP server</para>
 595         </listitem>
 596       </varlistentry>
 597         <varlistentry>
 598           <term><varname>UseDomains=</varname></term>
 599           <listitem>
 600             <para>When true (not the default), the domain name
 601             received from the DHCP server will be used for DNS
 602             resolution over this link. When a name cannot be resolved
 603             as specified, the domain name will be used a suffix and
 604             name resolution of that will be attempted.</para>
 605
 606             <para>This corresponds to the <option>domain</option>
 607             option in <citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 608             and should not be enabled on untrusted networks.</para>
 609           </listitem>
 610         </varlistentry>
 611         <varlistentry>
 612           <term><varname>UseRoutes=</varname></term>
 613           <listitem>
 614             <para>When true (the default), the static routes will be
 615             requested from the DHCP server and added to the routing
 616             table with metric of 1024.</para>
 617           </listitem>
 618         </varlistentry>
 619         <varlistentry>
 620           <term><varname>CriticalConnection=</varname></term>
 621           <listitem>
 622             <para>When true, the connection will never be torn down
 623             even if the DHCP lease expires. This is contrary to the
 624             DHCP specification, but may be the best choice if, say,
 625             the root filesystem relies on this connection. Defaults to
 626             false.</para>
 627           </listitem>
 628         </varlistentry>
 629         <varlistentry>
 630           <term><varname>ClientIdentifier=</varname></term>
 631           <listitem>
 632             <para>DHCP client identifier to use. Either <literal>mac</literal>
 633             to use the MAC address of the link or <literal>duid</literal>
 634             (the default) to use a RFC4361-compliant Client ID.</para>
 635           </listitem>
 636         </varlistentry>
 637         <varlistentry>
 638           <term><varname>VendorClassIdentifier=</varname></term>
 639           <listitem>
 640             <para>The vendor class identifier used to identify vendor
 641             type and configuration.</para>
 642           </listitem>
 643         </varlistentry>
 644         <varlistentry>
 645           <term><varname>RequestBroadcast=</varname></term>
 646           <listitem>
 647             <para>Request the server to use broadcast messages before
 648             the IP address has been configured. This is necessary for
 649             devices that cannot receive RAW packets, or that cannot
 650             receive packets at all before an IP address has been
 651             configured. On the other hand, this must not be enabled on
 652             networks where broadcasts are filtered out.</para>
 653           </listitem>
 654         </varlistentry>
 655         <varlistentry>
 656           <term><varname>RouteMetric=</varname></term>
 657           <listitem>
 658             <para>Set the routing metric for routes specified by the
 659             DHCP server.</para>
 660           </listitem>
 661         </varlistentry>
 662            </variablelist>
 663
 664   </refsect1>
 665
 666   <refsect1>
 667     <title>[Bridge] Section Options</title>
 668       <para>The <literal>[Bridge]</literal> section accepts the
 669       following keys.</para>
 670       <variablelist class='network-directives'>
 671         <varlistentry>
 672           <term><varname>UnicastFlood=</varname></term>
 673           <listitem>
 674             <para>A boolean. UnicastFlood configures whether a given port will flood
 675             unicast traffic for which there is no FDB entry. By default this
 676             flag is off.</para>
 677           </listitem>
 678         </varlistentry>
 679         <varlistentry>
 680           <term><varname>HairPin=</varname></term>
 681           <listitem>
 682             <para> A boolean. Configures whether traffic may be send back
 683             out of the port on which it was received.  By default, this
 684             flag is false. and the bridge will not forward traffic back
 685             out of the receiving port. By default the flag is off.</para>
 686           </listitem>
 687         </varlistentry>
 688         <varlistentry>
 689           <term><varname>BPDUGuard=</varname></term>
 690           <listitem>
 691             <para> A boolean. Configures whether STP Bridge Protocol Data Units will be
 692             processed by the bridge port. By default, the flag is false allowing BPDU
 693             processing. Turning this flag on will cause the port to stop processing
 694             STP Bridge Protocol Data Units. By default the flag is off.</para>
 695           </listitem>
 696         </varlistentry>
 697         <varlistentry>
 698           <term><varname>FastLeave=</varname></term>
 699           <listitem>
 700             <para> A boolean. This flag allows the bridge to immediately stop multicast
 701             traffic on a port that receives IGMP Leave message. It is only used with
 702             IGMP snooping if enabled on the bridge. By default the flag is off.</para>
 703           </listitem>
 704         </varlistentry>
 705         <varlistentry>
 706           <term><varname>RootBlock=</varname></term>
 707           <listitem>
 708             <para> A boolean. Configures whether a given port is allowed to
 709             become root port or not. Only used when STP is enabled on the bridge.
 710             By default the flag is off.</para>
 711           </listitem>
 712         </varlistentry>
 713         <varlistentry>
 714           <term><varname>Cost=</varname></term>
 715           <listitem>
 716             <para>Each port in a bridge may have different speed. Cost
 717             is used to decide which link to use. Faster interfaces
 718             should have lower costs</para>
 719           </listitem>
 720         </varlistentry>
 721       </variablelist>
 722   </refsect1>
 723   <refsect1>
 724     <title>[BridgeFDB] Section Options</title>
 725       <para>The <literal>[BridgeFDB]</literal> section manages the
 726       forwarding database table of a port and accepts the following
 727       keys. Specify several <literal>[BridgeFDB]</literal> sections to
 728       configure several static MAC table entries.</para>
 729
 730       <variablelist class='network-directives'>
 731         <varlistentry>
 732           <term><varname>MACAddress=</varname></term>
 733           <listitem>
 734             <para>As in the <literal>[Network]</literal> section. This
 735             key is mandatory.</para>
 736           </listitem>
 737         </varlistentry>
 738         <varlistentry>
 739           <term><varname>VLANId=</varname></term>
 740           <listitem>
 741             <para>The VLAN Id for the new static MAC table entry. If
 742             omitted, no VLAN Id info is appended to the new static MAC
 743             table entry.</para>
 744           </listitem>
 745         </varlistentry>
 746       </variablelist>
 747   </refsect1>
 748
 749   <refsect1>
 750     <title>Example</title>
 751     <example>
 752       <title>/etc/systemd/network/50-static.network</title>
 753
 754       <programlisting>[Match]
 755 Name=enp2s0
 756
 757 [Network]
 758 Address=192.168.0.15/24
 759 Gateway=192.168.0.1</programlisting>
 760     </example>
 761
 762     <example>
 763       <title>/etc/systemd/network/80-dhcp.network</title>
 764
 765       <programlisting>[Match]
 766 Name=en*
 767
 768 [Network]
 769 DHCP=yes</programlisting>
 770     </example>
 771
 772     <example>
 773       <title>/etc/systemd/network/bridge-static.network</title>
 774
 775       <programlisting>[Match]
 776 Name=bridge0
 777
 778 [Network]
 779 Address=192.168.0.15/24
 780 Gateway=192.168.0.1
 781 DNS=192.168.0.1</programlisting>
 782     </example>
 783
 784     <example>
 785       <title>/etc/systemd/network/bridge-slave-interface.network</title>
 786
 787       <programlisting>[Match]
 788 Name=enp2s0
 789
 790 [Network]
 791 Bridge=bridge0</programlisting>
 792     </example>
 793     <example>
 794       <title>/etc/systemd/network/ipip.network</title>
 795
 796       <programlisting>[Match]
 797 Name=em1
 798
 799 [Network]
 800 Tunnel=ipip-tun</programlisting>
 801     </example>
 802
 803     <example>
 804       <title>/etc/systemd/network/sit.network</title>
 805
 806       <programlisting>[Match]
 807 Name=em1
 808
 809 [Network]
 810 Tunnel=sit-tun</programlisting>
 811     </example>
 812
 813     <example>
 814       <title>/etc/systemd/network/gre.network</title>
 815
 816       <programlisting>[Match]
 817 Name=em1
 818
 819 [Network]
 820 Tunnel=gre-tun</programlisting>
 821     </example>
 822
 823     <example>
 824       <title>/etc/systemd/network/vti.network</title>
 825
 826       <programlisting>[Match]
 827 Name=em1
 828
 829 [Network]
 830 Tunnel=vti-tun</programlisting>
 831     </example>
 832   </refsect1>
 833
 834   <refsect1>
 835     <title>See Also</title>
 836     <para>
 837       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 838       <citerefentry><refentrytitle>systemd-networkd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 839       <citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 840       <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 841     </para>
 842   </refsect1>
 843
 844 </refentry>