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. As a special case, an empty file (file size 0) or symlink
  80     with the same name pointing to <filename>/dev/null</filename>,
  81     disable the configuration file entirely (it is "masked").</para>
  82   </refsect1>
  83
  84   <refsect1>
  85     <title>[Match] Section Options</title>
  86
  87       <para>The network file contains a <literal>[Match]</literal>
  88       section, which determines if a given network file may be applied
  89       to a given device; and a <literal>[Network]</literal> section
  90       specifying how the device should be configured. The first (in
  91       lexical order) of the network files that matches a given device
  92       is applied, all later files are ignored, even if they match as
  93       well.</para>
  94
  95       <para>A network file is said to match a device if each of the
  96       entries in the <literal>[Match]</literal> section matches, or if
  97       the section is empty. The following keys are accepted:</para>
  98
  99       <variablelist class='network-directives'>
 100         <varlistentry>
 101           <term><varname>MACAddress=</varname></term>
 102           <listitem>
 103             <para>The hardware address.</para>
 104           </listitem>
 105         </varlistentry>
 106         <varlistentry>
 107           <term><varname>Path=</varname></term>
 108           <listitem>
 109             <para>A whitespace-separated list of shell-style globs
 110             matching the persistent path, as exposed by the udev
 111             property <literal>ID_PATH</literal>.</para>
 112           </listitem>
 113         </varlistentry>
 114         <varlistentry>
 115           <term><varname>Driver=</varname></term>
 116           <listitem>
 117             <para>A whitespace-separated list of shell-style globs
 118             matching the driver currently bound to the device, as
 119             exposed by the udev property <literal>DRIVER</literal>
 120             of its parent device, or if that is not set the driver
 121             as exposed by <literal>ethtool -i</literal> of the
 122             device itself.</para>
 123           </listitem>
 124         </varlistentry>
 125         <varlistentry>
 126           <term><varname>Type=</varname></term>
 127           <listitem>
 128             <para>A whitespace-separated list of shell-style globs
 129             matching the device type, as exposed by the udev property
 130             <literal>DEVTYPE</literal>.</para>
 131           </listitem>
 132         </varlistentry>
 133         <varlistentry>
 134           <term><varname>Name=</varname></term>
 135           <listitem>
 136             <para>A whitespace-separated list of shell-style globs
 137             matching the device name, as exposed by the udev property
 138             <literal>INTERFACE</literal>.</para>
 139           </listitem>
 140         </varlistentry>
 141         <varlistentry>
 142           <term><varname>Host=</varname></term>
 143           <listitem>
 144             <para>Matches against the hostname or machine ID of the
 145             host. See <literal>ConditionHost=</literal> in
 146             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 147             for details.
 148             </para>
 149           </listitem>
 150         </varlistentry>
 151         <varlistentry>
 152           <term><varname>Virtualization=</varname></term>
 153           <listitem>
 154             <para>Checks whether the system is executed in a virtualized
 155             environment and optionally test whether it is a specific
 156             implementation. See <literal>ConditionVirtualization=</literal> in
 157             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 158             for details.
 159             </para>
 160           </listitem>
 161         </varlistentry>
 162         <varlistentry>
 163           <term><varname>KernelCommandLine=</varname></term>
 164           <listitem>
 165             <para>Checks whether a specific kernel command line option is
 166             set (or if prefixed with the exclamation mark unset). See
 167             <literal>ConditionKernelCommandLine=</literal> in
 168             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 169             for details.
 170             </para>
 171           </listitem>
 172         </varlistentry>
 173         <varlistentry>
 174           <term><varname>Architecture=</varname></term>
 175           <listitem>
 176             <para>Checks whether the system is running on a specific
 177             architecture. See <literal>ConditionArchitecture=</literal> in
 178             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 179             for details.
 180             </para>
 181           </listitem>
 182         </varlistentry>
 183       </variablelist>
 184
 185   </refsect1>
 186
 187   <refsect1>
 188     <title>[Link] Section Options</title>
 189
 190     <para> The <literal>[Link]</literal> section accepts the following keys:</para>
 191
 192     <variablelist class='network-directives'>
 193       <varlistentry>
 194         <term><varname>MACAddress=</varname></term>
 195         <listitem>
 196           <para>The hardware address.</para>
 197         </listitem>
 198       </varlistentry>
 199       <varlistentry>
 200         <term><varname>MTUBytes=</varname></term>
 201         <listitem>
 202           <para>The maximum transmission unit in bytes to set for the
 203           device. The usual suffixes K, M, G, are supported and are
 204           understood to the base of 1024.</para>
 205         </listitem>
 206       </varlistentry>
 207     </variablelist>
 208   </refsect1>
 209
 210   <refsect1>
 211     <title>[Network] Section Options</title>
 212
 213       <para>The <literal>[Network]</literal> section accepts the following keys:</para>
 214
 215       <variablelist class='network-directives'>
 216         <varlistentry>
 217           <term><varname>Description=</varname></term>
 218           <listitem>
 219             <para>A description of the device. This is only used for
 220             presentation purposes.</para>
 221           </listitem>
 222         </varlistentry>
 223         <varlistentry>
 224           <term><varname>DHCP=</varname></term>
 225           <listitem>
 226             <para>Enables DHCPv4 and/or DHCPv6 support. Accepts
 227             <literal>yes</literal>, <literal>no</literal>,
 228             <literal>ipv4</literal>, or <literal>ipv6</literal>.</para>
 229
 230             <para>Please note that by default the domain name
 231             specified through DHCP is not used for name resolution.
 232             See option <option>UseDomains=</option> below.</para>
 233           </listitem>
 234         </varlistentry>
 235         <varlistentry>
 236           <term><varname>DHCPServer=</varname></term>
 237           <listitem>
 238             <para>A boolean. Enables a basic DHCPv4 server on the
 239             device. Mostly useful for handing out leases to container
 240             instances.</para>
 241           </listitem>
 242         </varlistentry>
 243         <varlistentry>
 244           <term><varname>LinkLocalAddressing=</varname></term>
 245           <listitem>
 246             <para>Enables link-local address autoconfiguration. Accepts
 247             <literal>yes</literal>, <literal>no</literal>,
 248             <literal>ipv4</literal>, or <literal>ipv6</literal>. Defaults to
 249             <literal>ipv6</literal>.</para>
 250           </listitem>
 251         </varlistentry>
 252         <varlistentry>
 253           <term><varname>IPv4LLRoute=</varname></term>
 254           <listitem>
 255             <para>A boolean. When true, sets up the route needed for
 256             non-IPv4LL hosts to communicate with IPv4LL-only hosts. Defaults
 257             to false.
 258             </para>
 259           </listitem>
 260         </varlistentry>
 261         <varlistentry>
 262           <term><varname>IPv6Token=</varname></term>
 263           <listitem>
 264             <para>An IPv6 address with the top 64 bits unset. When set, indicates the
 265             64 bits interface part of SLAAC IPv6 addresses for this link. By default
 266             it is autogenerated.</para>
 267           </listitem>
 268         </varlistentry>
 269         <varlistentry>
 270           <term><varname>LLMNR=</varname></term>
 271           <listitem>
 272             <para>A boolean or <literal>resolve</literal>. When true, enables
 273             Link-Local Multicast Name Resolution on the link, when set to
 274             <literal>resolve</literal> only resolution is enabled, but not
 275             announcement. Defaults to true.</para>
 276           </listitem>
 277         </varlistentry>
 278         <varlistentry>
 279           <term><varname>LLDP=</varname></term>
 280           <listitem>
 281             <para>A boolean. When true, enables LLDP link receive support.
 282             </para>
 283           </listitem>
 284         </varlistentry>
 285         <varlistentry>
 286           <term><varname>BindCarrier=</varname></term>
 287           <listitem>
 288             <para>A port or a list of ports. When set, controls the
 289             behavior of the current interface. When all ports in the list
 290             are in an operational down state, the current interface is brought
 291             down. When at least one port has carrier, the current interface
 292             is brought up.
 293             </para>
 294           </listitem>
 295         </varlistentry>
 296         <varlistentry>
 297           <term><varname>Address=</varname></term>
 298           <listitem>
 299             <para>A static IPv4 or IPv6 address and its prefix length,
 300             separated by a <literal>/</literal> character. Specify
 301             this key more than once to configure several addresses.
 302             The format of the address must be as described in
 303             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 304             This is a short-hand for an [Address] section only
 305             containing an Address key (see below). This option may be
 306             specified more than once.
 307             </para>
 308
 309             <para>If the specified address is 0.0.0.0 (for IPv4) or
 310             [::] (for IPv6), a new address range of the requested size
 311             is automatically allocated from a system-wide pool of
 312             unused ranges. The allocated range is checked against all
 313             current network interfaces and all known network
 314             configuration files to avoid address range conflicts. The
 315             default system-wide pool consists of 192.168.0.0/16,
 316             172.16.0.0/12 and 10.0.0.0/8 for IPv4, and fc00::/7 for
 317             IPv6. This functionality is useful to manage a large
 318             number of dynamically created network interfaces with the
 319             same network configuration and automatic address range
 320             assignment.</para>
 321
 322           </listitem>
 323         </varlistentry>
 324         <varlistentry>
 325           <term><varname>Gateway=</varname></term>
 326           <listitem>
 327             <para>The gateway address, which must be in the format
 328             described in
 329             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 330             This is a short-hand for a [Route] section only containing
 331             a Gateway key. This option may be specified more than
 332             once.</para>
 333           </listitem>
 334         </varlistentry>
 335         <varlistentry>
 336           <term><varname>DNS=</varname></term>
 337           <listitem>
 338             <para>A DNS server address, which must be in the format
 339             described in
 340             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 341             This option may be specified more than once.</para>
 342           </listitem>
 343         </varlistentry>
 344         <varlistentry>
 345           <term><varname>Domains=</varname></term>
 346           <listitem>
 347             <para>The domains used for DNS resolution over this link.</para>
 348           </listitem>
 349         </varlistentry>
 350         <varlistentry>
 351           <term><varname>NTP=</varname></term>
 352           <listitem>
 353             <para>An NTP server address. This option may be specified more than once.</para>
 354           </listitem>
 355         </varlistentry>
 356         <varlistentry>
 357           <term><varname>IPForward=</varname></term>
 358           <listitem><para>Configures IP forwarding for the network
 359           interface. If enabled incoming packets on the network
 360           interface will be forwarded to other interfaces according to
 361           the routing table. Takes either a boolean argument, or the
 362           values <literal>ipv4</literal> or <literal>ipv6</literal>,
 363           which only enables IP forwarding for the specified address
 364           family, or <literal>kernel</literal>, which preserves existing sysctl settings.
 365           This controls the
 366           <filename>net.ipv4.conf.&lt;interface&gt;.forwarding</filename>
 367           and
 368           <filename>net.ipv6.conf.&lt;interface&gt;.forwarding</filename>
 369           sysctl options of the network interface (see <ulink
 370           url="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">ip-sysctl.txt</ulink>
 371           for details about sysctl options). Defaults to
 372           <literal>no</literal>.</para>
 373
 374          <para>Note: unless this option is turned on, or set to <literal>kernel</literal>,
 375           no IP forwarding is done on this interface, even if this is
 376           globally turned on in the kernel, with the
 377           <filename>net.ipv4.ip_forward</filename>,
 378           <filename>net.ipv4.conf.all.forwarding</filename>, and
 379           <filename>net.ipv6.conf.all.forwarding</filename> sysctl
 380           options.</para>
 381           </listitem>
 382         </varlistentry>
 383         <varlistentry>
 384           <term><varname>IPMasquerade=</varname></term>
 385           <listitem><para>Configures IP masquerading for the network
 386           interface. If enabled packets forwarded from the network
 387           interface will be appear as coming from the local host.
 388           Takes a boolean argument. Implies
 389           <varname>IPForward=ipv4</varname>. Defaults to
 390           <literal>no</literal>.</para></listitem>
 391         </varlistentry>
 392         <varlistentry>
 393           <term><varname>IPv6PrivacyExtensions=</varname></term>
 394           <listitem><para>Configures use of stateless temporary
 395           addresses that change over time (see <ulink
 396           url="https://tools.ietf.org/html/rfc4941">RFC 4941</ulink>,
 397           Privacy Extensions for Stateless Address Autoconfiguration
 398           in IPv6). Takes a boolean or the special values
 399           <literal>prefer-public</literal> and
 400           <literal>kernel</literal>. When true enables the privacy
 401           extensions and prefers temporary addresses over public
 402           addresses. When <literal>prefer-public</literal> enables the
 403           privacy extensions, but prefers public addresses over
 404           temporary addresses. When false, the privacy extensions
 405           remain disabled. When <literal>kernel</literal> the kernel's
 406           default setting will be left in place.  Defaults to
 407           <literal>no</literal>.</para></listitem>
 408         </varlistentry>
 409         <varlistentry>
 410           <term><varname>Bridge=</varname></term>
 411           <listitem>
 412             <para>The name of the bridge to add the link to.</para>
 413           </listitem>
 414         </varlistentry>
 415         <varlistentry>
 416           <term><varname>Bond=</varname></term>
 417           <listitem>
 418             <para>The name of the bond to add the link to.</para>
 419           </listitem>
 420         </varlistentry>
 421         <varlistentry>
 422           <term><varname>VLAN=</varname></term>
 423           <listitem>
 424             <para>The name of a VLAN to create on the link. This
 425             option may be specified more than once.</para>
 426           </listitem>
 427         </varlistentry>
 428         <varlistentry>
 429           <term><varname>MACVLAN=</varname></term>
 430           <listitem>
 431             <para>The name of a MACVLAN to create on the link. This
 432             option may be specified more than once.</para>
 433           </listitem>
 434         </varlistentry>
 435         <varlistentry>
 436           <term><varname>VXLAN=</varname></term>
 437           <listitem>
 438             <para>The name of a VXLAN to create on the link. This
 439             option may be specified more than once.</para>
 440           </listitem>
 441         </varlistentry>
 442         <varlistentry>
 443           <term><varname>Tunnel=</varname></term>
 444           <listitem>
 445             <para>The name of a Tunnel to create on the link. This
 446             option may be specified more than once.</para>
 447           </listitem>
 448         </varlistentry>
 449       </variablelist>
 450
 451   </refsect1>
 452
 453   <refsect1>
 454     <title>[Address] Section Options</title>
 455
 456       <para>An <literal>[Address]</literal> section accepts the
 457       following keys. Specify several <literal>[Address]</literal>
 458       sections to configure several addresses.</para>
 459
 460       <variablelist class='network-directives'>
 461         <varlistentry>
 462           <term><varname>Address=</varname></term>
 463           <listitem>
 464             <para>As in the <literal>[Network]</literal> section. This
 465             key is mandatory.</para>
 466           </listitem>
 467         </varlistentry>
 468         <varlistentry>
 469           <term><varname>Peer=</varname></term>
 470           <listitem>
 471             <para>The peer address in a point-to-point connection.
 472             Accepts the same format as the <literal>Address</literal>
 473             key.</para>
 474           </listitem>
 475         </varlistentry>
 476         <varlistentry>
 477           <term><varname>Broadcast=</varname></term>
 478           <listitem>
 479             <para>The broadcast 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 key only applies to IPv4 addresses. If it is not
 483             given, it is derived from the <literal>Address</literal>
 484             key.</para>
 485           </listitem>
 486         </varlistentry>
 487         <varlistentry>
 488           <term><varname>Label=</varname></term>
 489           <listitem>
 490             <para>An address label.</para>
 491           </listitem>
 492         </varlistentry>
 493       </variablelist>
 494   </refsect1>
 495
 496   <refsect1>
 497     <title>[Route] Section Options</title>
 498       <para>The <literal>[Route]</literal> section accepts the
 499       following keys. Specify several <literal>[Route]</literal>
 500       sections to configure several routes.</para>
 501
 502       <variablelist class='network-directives'>
 503         <varlistentry>
 504           <term><varname>Gateway=</varname></term>
 505           <listitem>
 506             <para>As in the <literal>[Network]</literal> section.</para>
 507           </listitem>
 508         </varlistentry>
 509         <varlistentry>
 510           <term><varname>Destination=</varname></term>
 511           <listitem>
 512             <para>The destination prefix of the route. Possibly
 513             followed by a slash and the prefixlength. If omitted, a
 514             full-length host route is assumed.</para>
 515           </listitem>
 516         </varlistentry>
 517         <varlistentry>
 518           <term><varname>Source=</varname></term>
 519           <listitem>
 520             <para>The source prefix of the route. Possibly followed by
 521             a slash and the prefixlength. If omitted, a full-length
 522             host route is assumed.</para>
 523           </listitem>
 524         </varlistentry>
 525         <varlistentry>
 526           <term><varname>Metric=</varname></term>
 527           <listitem>
 528             <para>The metric of the route. An unsigned integer</para>
 529           </listitem>
 530         </varlistentry>
 531         <varlistentry>
 532           <term><varname>Scope=</varname></term>
 533           <listitem>
 534             <para>The scope of the route. One of the values <literal>global</literal>,
 535             <literal>link</literal> or <literal>host</literal>. Defaults to
 536             <literal>global</literal>.</para>
 537           </listitem>
 538         </varlistentry>
 539       </variablelist>
 540   </refsect1>
 541
 542   <refsect1>
 543     <title>[DHCP] Section Options</title>
 544       <para>The <literal>[DHCP]</literal> section accepts the following keys:</para>
 545
 546       <variablelist class='network-directives'>
 547         <varlistentry>
 548           <term><varname>UseDNS=</varname></term>
 549           <listitem>
 550             <para>When true (the default), the DNS servers received
 551             from the DHCP server will be used and take precedence over
 552             any statically configured ones.</para>
 553
 554             <para>This corresponds to the <option>nameserver</option>
 555             option in <citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 556           </listitem>
 557         </varlistentry>
 558         <varlistentry>
 559           <term><varname>UseNTP=</varname></term>
 560           <listitem>
 561             <para>When true (the default), the NTP servers received
 562             from the DHCP server will be used by systemd-timesyncd
 563             and take precedence over any statically configured ones.</para>
 564           </listitem>
 565         </varlistentry>
 566         <varlistentry>
 567           <term><varname>UseMTU=</varname></term>
 568           <listitem>
 569             <para>When true, the interface maximum transmission unit
 570             from the DHCP server will be used on the current link.
 571             Defaults to false.</para>
 572           </listitem>
 573         </varlistentry>
 574         <varlistentry>
 575           <term><varname>SendHostname=</varname></term>
 576           <listitem>
 577             <para>When true (the default), the machine's hostname will
 578             be sent to the DHCP server.</para>
 579           </listitem>
 580         </varlistentry>
 581         <varlistentry>
 582           <term><varname>UseHostname=</varname></term>
 583           <listitem>
 584             <para>When true (the default), the hostname received from
 585             the DHCP server will be used as the transient hostname.
 586             </para>
 587           </listitem>
 588         </varlistentry>
 589         <varlistentry>
 590         <term><varname>Hostname=</varname></term>
 591         <listitem>
 592           <para>Use this value for the hostname which is sent to the
 593           DHCP server, instead of machine's hostname.</para>
 594         </listitem>
 595       </varlistentry>
 596         <varlistentry>
 597           <term><varname>UseDomains=</varname></term>
 598           <listitem>
 599             <para>When true (not the default), the domain name
 600             received from the DHCP server will be used for DNS
 601             resolution over this link. When a name cannot be resolved
 602             as specified, the domain name will be used a suffix and
 603             name resolution of that will be attempted.</para>
 604
 605             <para>This corresponds to the <option>domain</option>
 606             option in <citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 607             and should not be enabled on untrusted networks.</para>
 608           </listitem>
 609         </varlistentry>
 610         <varlistentry>
 611           <term><varname>UseRoutes=</varname></term>
 612           <listitem>
 613             <para>When true (the default), the static routes will be
 614             requested from the DHCP server and added to the routing
 615             table with metric of 1024.</para>
 616           </listitem>
 617         </varlistentry>
 618         <varlistentry>
 619           <term><varname>CriticalConnection=</varname></term>
 620           <listitem>
 621             <para>When true, the connection will never be torn down
 622             even if the DHCP lease expires. This is contrary to the
 623             DHCP specification, but may be the best choice if, say,
 624             the root filesystem relies on this connection. Defaults to
 625             false.</para>
 626           </listitem>
 627         </varlistentry>
 628         <varlistentry>
 629           <term><varname>ClientIdentifier=</varname></term>
 630           <listitem>
 631             <para>DHCP client identifier to use. Either <literal>mac</literal>
 632             to use the MAC address of the link or <literal>duid</literal>
 633             (the default) to use a RFC4361-compliant Client ID.</para>
 634           </listitem>
 635         </varlistentry>
 636         <varlistentry>
 637           <term><varname>VendorClassIdentifier=</varname></term>
 638           <listitem>
 639             <para>The vendor class identifier used to identify vendor
 640             type and configuration.</para>
 641           </listitem>
 642         </varlistentry>
 643         <varlistentry>
 644           <term><varname>RequestBroadcast=</varname></term>
 645           <listitem>
 646             <para>Request the server to use broadcast messages before
 647             the IP address has been configured. This is necessary for
 648             devices that cannot receive RAW packets, or that cannot
 649             receive packets at all before an IP address has been
 650             configured. On the other hand, this must not be enabled on
 651             networks where broadcasts are filtered out.</para>
 652           </listitem>
 653         </varlistentry>
 654         <varlistentry>
 655           <term><varname>RouteMetric=</varname></term>
 656           <listitem>
 657             <para>Set the routing metric for routes specified by the
 658             DHCP server.</para>
 659           </listitem>
 660         </varlistentry>
 661            </variablelist>
 662
 663   </refsect1>
 664
 665   <refsect1>
 666     <title>[Bridge] Section Options</title>
 667       <para>The <literal>[Bridge]</literal> section accepts the
 668       following keys.</para>
 669       <variablelist class='network-directives'>
 670         <varlistentry>
 671           <term><varname>UnicastFlood=</varname></term>
 672           <listitem>
 673             <para>A boolean. Controls whether the bridge should flood
 674             traffic for which an FDB entry is missing and the destination
 675             is unknown through this port. Defaults to on.
 676             </para>
 677           </listitem>
 678         </varlistentry>
 679         <varlistentry>
 680           <term><varname>HairPin=</varname></term>
 681           <listitem>
 682             <para>A boolean. Configures whether traffic may be sent 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.</para>
 686           </listitem>
 687         </varlistentry>
 688         <varlistentry>
 689           <term><varname>UseBPDU=</varname></term>
 690           <listitem>
 691             <para>A boolean. Configures whether STP Bridge Protocol Data Units will be
 692             processed by the bridge port. Defaults to yes.</para>
 693           </listitem>
 694         </varlistentry>
 695         <varlistentry>
 696           <term><varname>FastLeave=</varname></term>
 697           <listitem>
 698             <para>A boolean. This flag allows the bridge to immediately stop multicast
 699             traffic on a port that receives IGMP Leave message. It is only used with
 700             IGMP snooping if enabled on the bridge. Defaults to off.</para>
 701           </listitem>
 702         </varlistentry>
 703         <varlistentry>
 704           <term><varname>AllowPortToBeRoot=</varname></term>
 705           <listitem>
 706             <para>A boolean. Configures whether a given port is allowed to
 707             become a root port. Only used when STP is enabled on the bridge.
 708             Defaults to on.</para>
 709           </listitem>
 710         </varlistentry>
 711         <varlistentry>
 712           <term><varname>Cost=</varname></term>
 713           <listitem>
 714             <para>Sets the "cost" of sending packets of this interface.
 715             Each port in a bridge may have different speed and the cost
 716             is used to decide which link to use. Faster interfaces
 717             should have lower costs.</para>
 718           </listitem>
 719         </varlistentry>
 720       </variablelist>
 721   </refsect1>
 722   <refsect1>
 723     <title>[BridgeFDB] Section Options</title>
 724       <para>The <literal>[BridgeFDB]</literal> section manages the
 725       forwarding database table of a port and accepts the following
 726       keys. Specify several <literal>[BridgeFDB]</literal> sections to
 727       configure several static MAC table entries.</para>
 728
 729       <variablelist class='network-directives'>
 730         <varlistentry>
 731           <term><varname>MACAddress=</varname></term>
 732           <listitem>
 733             <para>As in the <literal>[Network]</literal> section. This
 734             key is mandatory.</para>
 735           </listitem>
 736         </varlistentry>
 737         <varlistentry>
 738           <term><varname>VLANId=</varname></term>
 739           <listitem>
 740             <para>The VLAN Id for the new static MAC table entry. If
 741             omitted, no VLAN Id info is appended to the new static MAC
 742             table entry.</para>
 743           </listitem>
 744         </varlistentry>
 745       </variablelist>
 746   </refsect1>
 747
 748   <refsect1>
 749     <title>Example</title>
 750     <example>
 751       <title>/etc/systemd/network/50-static.network</title>
 752
 753       <programlisting>[Match]
 754 Name=enp2s0
 755
 756 [Network]
 757 Address=192.168.0.15/24
 758 Gateway=192.168.0.1</programlisting>
 759     </example>
 760
 761     <example>
 762       <title>/etc/systemd/network/80-dhcp.network</title>
 763
 764       <programlisting>[Match]
 765 Name=en*
 766
 767 [Network]
 768 DHCP=yes</programlisting>
 769     </example>
 770
 771     <example>
 772       <title>/etc/systemd/network/bridge-static.network</title>
 773
 774       <programlisting>[Match]
 775 Name=bridge0
 776
 777 [Network]
 778 Address=192.168.0.15/24
 779 Gateway=192.168.0.1
 780 DNS=192.168.0.1</programlisting>
 781     </example>
 782
 783     <example>
 784       <title>/etc/systemd/network/bridge-slave-interface.network</title>
 785
 786       <programlisting>[Match]
 787 Name=enp2s0
 788
 789 [Network]
 790 Bridge=bridge0</programlisting>
 791     </example>
 792     <example>
 793       <title>/etc/systemd/network/ipip.network</title>
 794
 795       <programlisting>[Match]
 796 Name=em1
 797
 798 [Network]
 799 Tunnel=ipip-tun</programlisting>
 800     </example>
 801
 802     <example>
 803       <title>/etc/systemd/network/sit.network</title>
 804
 805       <programlisting>[Match]
 806 Name=em1
 807
 808 [Network]
 809 Tunnel=sit-tun</programlisting>
 810     </example>
 811
 812     <example>
 813       <title>/etc/systemd/network/gre.network</title>
 814
 815       <programlisting>[Match]
 816 Name=em1
 817
 818 [Network]
 819 Tunnel=gre-tun</programlisting>
 820     </example>
 821
 822     <example>
 823       <title>/etc/systemd/network/vti.network</title>
 824
 825       <programlisting>[Match]
 826 Name=em1
 827
 828 [Network]
 829 Tunnel=vti-tun</programlisting>
 830     </example>
 831
 832     <example>
 833       <title>/etc/systemd/network/bond.network</title>
 834
 835       <programlisting>[Match]
 836 Name=bond1
 837
 838 [Network]
 839 DHCP=yes
 840 </programlisting>
 841     </example>
 842
 843   </refsect1>
 844
 845   <refsect1>
 846     <title>See Also</title>
 847     <para>
 848       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 849       <citerefentry><refentrytitle>systemd-networkd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 850       <citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 851       <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 852     </para>
 853   </refsect1>
 854
 855 </refentry>