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     disables 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 client 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 DHCPv4 server support. Defaults
 239             to <literal>no</literal>. Further settings for the DHCP
 240             server may be set in the <literal>[DHCPServer]</literal>
 241             section described below.</para>
 242           </listitem>
 243         </varlistentry>
 244         <varlistentry>
 245           <term><varname>LinkLocalAddressing=</varname></term>
 246           <listitem>
 247             <para>Enables link-local address autoconfiguration. Accepts
 248             <literal>yes</literal>, <literal>no</literal>,
 249             <literal>ipv4</literal>, or <literal>ipv6</literal>. Defaults to
 250             <literal>ipv6</literal>.</para>
 251           </listitem>
 252         </varlistentry>
 253         <varlistentry>
 254           <term><varname>IPv4LLRoute=</varname></term>
 255           <listitem>
 256             <para>A boolean. When true, sets up the route needed for
 257             non-IPv4LL hosts to communicate with IPv4LL-only hosts. Defaults
 258             to false.
 259             </para>
 260           </listitem>
 261         </varlistentry>
 262         <varlistentry>
 263           <term><varname>IPv6Token=</varname></term>
 264           <listitem>
 265             <para>An IPv6 address with the top 64 bits unset. When set, indicates the
 266             64-bit interface part of SLAAC IPv6 addresses for this link. By default,
 267             it is autogenerated.</para>
 268           </listitem>
 269         </varlistentry>
 270         <varlistentry>
 271           <term><varname>LLMNR=</varname></term>
 272           <listitem>
 273             <para>A boolean or <literal>resolve</literal>. When true, enables
 274             Link-Local Multicast Name Resolution on the link. When set to
 275             <literal>resolve</literal>, only resolution is enabled, but not
 276             announcement. Defaults to true.</para>
 277           </listitem>
 278         </varlistentry>
 279         <varlistentry>
 280           <term><varname>LLDP=</varname></term>
 281           <listitem>
 282             <para>A boolean. When true, enables LLDP link receive support.
 283             </para>
 284           </listitem>
 285         </varlistentry>
 286         <varlistentry>
 287           <term><varname>BindCarrier=</varname></term>
 288           <listitem>
 289             <para>A port or a list of ports. When set, controls the
 290             behavior of the current interface. When all ports in the list
 291             are in an operational down state, the current interface is brought
 292             down. When at least one port has carrier, the current interface
 293             is brought up.
 294             </para>
 295           </listitem>
 296         </varlistentry>
 297         <varlistentry>
 298           <term><varname>Address=</varname></term>
 299           <listitem>
 300             <para>A static IPv4 or IPv6 address and its prefix length,
 301             separated by a <literal>/</literal> character. Specify
 302             this key more than once to configure several addresses.
 303             The format of the address must be as described in
 304             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 305             This is a short-hand for an [Address] section only
 306             containing an Address key (see below). This option may be
 307             specified more than once.
 308             </para>
 309
 310             <para>If the specified address is 0.0.0.0 (for IPv4) or
 311             [::] (for IPv6), a new address range of the requested size
 312             is automatically allocated from a system-wide pool of
 313             unused ranges. The allocated range is checked against all
 314             current network interfaces and all known network
 315             configuration files to avoid address range conflicts. The
 316             default system-wide pool consists of 192.168.0.0/16,
 317             172.16.0.0/12 and 10.0.0.0/8 for IPv4, and fc00::/7 for
 318             IPv6. This functionality is useful to manage a large
 319             number of dynamically created network interfaces with the
 320             same network configuration and automatic address range
 321             assignment.</para>
 322
 323           </listitem>
 324         </varlistentry>
 325         <varlistentry>
 326           <term><varname>Gateway=</varname></term>
 327           <listitem>
 328             <para>The gateway address, which must be in the format
 329             described in
 330             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 331             This is a short-hand for a [Route] section only containing
 332             a Gateway key. This option may be specified more than
 333             once.</para>
 334           </listitem>
 335         </varlistentry>
 336         <varlistentry>
 337           <term><varname>DNS=</varname></term>
 338           <listitem>
 339             <para>A DNS server address, which must be in the format
 340             described in
 341             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 342             This option may be specified more than once.</para>
 343           </listitem>
 344         </varlistentry>
 345         <varlistentry>
 346           <term><varname>Domains=</varname></term>
 347           <listitem>
 348             <para>The domains used for DNS resolution over this link.</para>
 349           </listitem>
 350         </varlistentry>
 351         <varlistentry>
 352           <term><varname>NTP=</varname></term>
 353           <listitem>
 354             <para>An NTP server address. This option may be specified more than once.</para>
 355           </listitem>
 356         </varlistentry>
 357         <varlistentry>
 358           <term><varname>IPForward=</varname></term>
 359           <listitem><para>Configures IP forwarding for the network
 360           interface. If enabled, incoming packets on the network
 361           interface will be forwarded to other interfaces according to
 362           the routing table. Takes either a boolean argument, or the
 363           values <literal>ipv4</literal> or <literal>ipv6</literal>,
 364           which only enables IP forwarding for the specified address
 365           family, or <literal>kernel</literal>, which preserves existing sysctl settings.
 366           This controls the
 367           <filename>net.ipv4.conf.&lt;interface&gt;.forwarding</filename>
 368           and
 369           <filename>net.ipv6.conf.&lt;interface&gt;.forwarding</filename>
 370           sysctl options of the network interface (see <ulink
 371           url="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">ip-sysctl.txt</ulink>
 372           for details about sysctl options). Defaults to
 373           <literal>no</literal>.</para>
 374
 375          <para>Note: unless this option is turned on, or set to <literal>kernel</literal>,
 376           no IP forwarding is done on this interface, even if this is
 377           globally turned on in the kernel, with the
 378           <filename>net.ipv4.ip_forward</filename>,
 379           <filename>net.ipv4.conf.all.forwarding</filename>, and
 380           <filename>net.ipv6.conf.all.forwarding</filename> sysctl
 381           options.</para>
 382           </listitem>
 383         </varlistentry>
 384         <varlistentry>
 385           <term><varname>IPMasquerade=</varname></term>
 386           <listitem><para>Configures IP masquerading for the network
 387           interface. If enabled, packets forwarded from the network
 388           interface will be appear as coming from the local host.
 389           Takes a boolean argument. Implies
 390           <varname>IPForward=ipv4</varname>. Defaults to
 391           <literal>no</literal>.</para></listitem>
 392         </varlistentry>
 393         <varlistentry>
 394           <term><varname>IPv6PrivacyExtensions=</varname></term>
 395           <listitem><para>Configures use of stateless temporary
 396           addresses that change over time (see <ulink
 397           url="https://tools.ietf.org/html/rfc4941">RFC 4941</ulink>,
 398           Privacy Extensions for Stateless Address Autoconfiguration
 399           in IPv6). Takes a boolean or the special values
 400           <literal>prefer-public</literal> and
 401           <literal>kernel</literal>. When true, enables the privacy
 402           extensions and prefers temporary addresses over public
 403           addresses. When <literal>prefer-public</literal>, enables the
 404           privacy extensions, but prefers public addresses over
 405           temporary addresses. When false, the privacy extensions
 406           remain disabled. When <literal>kernel</literal>, the kernel's
 407           default setting will be left in place.  Defaults to
 408           <literal>no</literal>.</para></listitem>
 409         </varlistentry>
 410         <varlistentry>
 411           <term><varname>IPv6AcceptRouterAdvertisements=</varname></term>
 412           <listitem><para>Force the setting of the <filename>accept_ra</filename>
 413           (router advertisements) setting for the interface.
 414           When unset, the kernel default is used, and router
 415           advertisements are accepted only when local forwarding
 416           is disabled for that interface.
 417           Takes a boolean. If true, router advertisements are
 418           accepted, when false, router advertisements are ignored,
 419           independently of the local forwarding state.</para>
 420
 421           <para>See
 422           <ulink url="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">ip-sysctl.txt</ulink>
 423           in the kernel documentation, but note that systemd's
 424           setting of <constant>1</constant> corresponds to
 425           kernel's setting of <constant>2</constant>.</para>
 426         </listitem>
 427         </varlistentry>
 428         <varlistentry>
 429           <term><varname>IPv6DuplicateAddressDetection=</varname></term>
 430           <listitem><para>Configures the amount of IPv6 Duplicate
 431           Address Detection (DAD) probes to send. Defaults to unset.
 432         </para></listitem>
 433         </varlistentry>
 434         <varlistentry>
 435           <term><varname>Bridge=</varname></term>
 436           <listitem>
 437             <para>The name of the bridge to add the link to.</para>
 438           </listitem>
 439         </varlistentry>
 440         <varlistentry>
 441           <term><varname>Bond=</varname></term>
 442           <listitem>
 443             <para>The name of the bond to add the link to.</para>
 444           </listitem>
 445         </varlistentry>
 446         <varlistentry>
 447           <term><varname>VLAN=</varname></term>
 448           <listitem>
 449             <para>The name of a VLAN to create on the link. This
 450             option may be specified more than once.</para>
 451           </listitem>
 452         </varlistentry>
 453         <varlistentry>
 454           <term><varname>MACVLAN=</varname></term>
 455           <listitem>
 456             <para>The name of a MACVLAN to create on the link. This
 457             option may be specified more than once.</para>
 458           </listitem>
 459         </varlistentry>
 460         <varlistentry>
 461           <term><varname>VXLAN=</varname></term>
 462           <listitem>
 463             <para>The name of a VXLAN to create on the link. This
 464             option may be specified more than once.</para>
 465           </listitem>
 466         </varlistentry>
 467         <varlistentry>
 468           <term><varname>Tunnel=</varname></term>
 469           <listitem>
 470             <para>The name of a Tunnel to create on the link. This
 471             option may be specified more than once.</para>
 472           </listitem>
 473         </varlistentry>
 474       </variablelist>
 475
 476   </refsect1>
 477
 478   <refsect1>
 479     <title>[Address] Section Options</title>
 480
 481       <para>An <literal>[Address]</literal> section accepts the
 482       following keys. Specify several <literal>[Address]</literal>
 483       sections to configure several addresses.</para>
 484
 485       <variablelist class='network-directives'>
 486         <varlistentry>
 487           <term><varname>Address=</varname></term>
 488           <listitem>
 489             <para>As in the <literal>[Network]</literal> section. This
 490             key is mandatory.</para>
 491           </listitem>
 492         </varlistentry>
 493         <varlistentry>
 494           <term><varname>Peer=</varname></term>
 495           <listitem>
 496             <para>The peer address in a point-to-point connection.
 497             Accepts the same format as the <literal>Address</literal>
 498             key.</para>
 499           </listitem>
 500         </varlistentry>
 501         <varlistentry>
 502           <term><varname>Broadcast=</varname></term>
 503           <listitem>
 504             <para>The broadcast address, which must be in the format
 505             described in
 506             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 507             This key only applies to IPv4 addresses. If it is not
 508             given, it is derived from the <literal>Address</literal>
 509             key.</para>
 510           </listitem>
 511         </varlistentry>
 512         <varlistentry>
 513           <term><varname>Label=</varname></term>
 514           <listitem>
 515             <para>An address label.</para>
 516           </listitem>
 517         </varlistentry>
 518       </variablelist>
 519   </refsect1>
 520
 521   <refsect1>
 522     <title>[Route] Section Options</title>
 523       <para>The <literal>[Route]</literal> section accepts the
 524       following keys. Specify several <literal>[Route]</literal>
 525       sections to configure several routes.</para>
 526
 527       <variablelist class='network-directives'>
 528         <varlistentry>
 529           <term><varname>Gateway=</varname></term>
 530           <listitem>
 531             <para>As in the <literal>[Network]</literal> section.</para>
 532           </listitem>
 533         </varlistentry>
 534         <varlistentry>
 535           <term><varname>Destination=</varname></term>
 536           <listitem>
 537             <para>The destination prefix of the route. Possibly
 538             followed by a slash and the prefix length. If omitted, a
 539             full-length host route is assumed.</para>
 540           </listitem>
 541         </varlistentry>
 542         <varlistentry>
 543           <term><varname>Source=</varname></term>
 544           <listitem>
 545             <para>The source prefix of the route. Possibly followed by
 546             a slash and the prefix length. If omitted, a full-length
 547             host route is assumed.</para>
 548           </listitem>
 549         </varlistentry>
 550         <varlistentry>
 551           <term><varname>Metric=</varname></term>
 552           <listitem>
 553             <para>The metric of the route (an unsigned integer).</para>
 554           </listitem>
 555         </varlistentry>
 556         <varlistentry>
 557           <term><varname>Scope=</varname></term>
 558           <listitem>
 559             <para>The scope of the route, which can be <literal>global</literal>,
 560             <literal>link</literal> or <literal>host</literal>. Defaults to
 561             <literal>global</literal>.</para>
 562           </listitem>
 563         </varlistentry>
 564         <varlistentry>
 565           <term><varname>PreferredSource=</varname></term>
 566           <listitem>
 567             <para>The preferred source address of the route. The address
 568             must be in the format described in
 569             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
 570           </listitem>
 571         </varlistentry>
 572       </variablelist>
 573   </refsect1>
 574
 575   <refsect1>
 576     <title>[DHCP] Section Options</title>
 577       <para>The <literal>[DHCP]</literal> section configures the
 578       DHCPv4 and DHCP6 client, if it is enabled with the
 579       <varname>DHCP=</varname> setting described above:</para>
 580
 581       <variablelist class='network-directives'>
 582         <varlistentry>
 583           <term><varname>UseDNS=</varname></term>
 584           <listitem>
 585             <para>When true (the default), the DNS servers received
 586             from the DHCP server will be used and take precedence over
 587             any statically configured ones.</para>
 588
 589             <para>This corresponds to the <option>nameserver</option>
 590             option in <citerefentry
 591             project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 592           </listitem>
 593         </varlistentry>
 594         <varlistentry>
 595           <term><varname>UseNTP=</varname></term>
 596           <listitem>
 597             <para>When true (the default), the NTP servers received
 598             from the DHCP server will be used by systemd-timesyncd
 599             and take precedence over any statically configured ones.</para>
 600           </listitem>
 601         </varlistentry>
 602         <varlistentry>
 603           <term><varname>UseMTU=</varname></term>
 604           <listitem>
 605             <para>When true, the interface maximum transmission unit
 606             from the DHCP server will be used on the current link.
 607             Defaults to false.</para>
 608           </listitem>
 609         </varlistentry>
 610         <varlistentry>
 611           <term><varname>SendHostname=</varname></term>
 612           <listitem>
 613             <para>When true (the default), the machine's hostname will
 614             be sent to the DHCP server.</para>
 615           </listitem>
 616         </varlistentry>
 617         <varlistentry>
 618           <term><varname>UseHostname=</varname></term>
 619           <listitem>
 620             <para>When true (the default), the hostname received from
 621             the DHCP server will be set as the transient hostname of the system
 622             </para>
 623           </listitem>
 624         </varlistentry>
 625         <varlistentry>
 626         <term><varname>Hostname=</varname></term>
 627         <listitem>
 628           <para>Use this value for the hostname which is sent to the
 629           DHCP server, instead of machine's hostname.</para>
 630         </listitem>
 631       </varlistentry>
 632         <varlistentry>
 633           <term><varname>UseDomains=</varname></term>
 634           <listitem>
 635             <para>When true (not the default), the domain name
 636             received from the DHCP server will be used for DNS
 637             resolution over this link. When a name cannot be resolved
 638             as specified, the domain name will be used a suffix and
 639             name resolution of that will be attempted.</para>
 640
 641             <para>This corresponds to the <option>domain</option>
 642             option in <citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 643             and should not be enabled on untrusted networks.</para>
 644           </listitem>
 645         </varlistentry>
 646         <varlistentry>
 647           <term><varname>UseRoutes=</varname></term>
 648           <listitem>
 649             <para>When true (the default), the static routes will be
 650             requested from the DHCP server and added to the routing
 651             table with a metric of 1024.</para>
 652           </listitem>
 653         </varlistentry>
 654
 655         <varlistentry>
 656           <term><varname>UseTimezone=</varname></term>
 657
 658           <listitem><para>When true, the timezone received from the
 659           DHCP server will be set as as timezone of the local
 660           system. Defaults to <literal>no</literal>.</para></listitem>
 661         </varlistentry>
 662
 663         <varlistentry>
 664           <term><varname>CriticalConnection=</varname></term>
 665           <listitem>
 666             <para>When true, the connection will never be torn down
 667             even if the DHCP lease expires. This is contrary to the
 668             DHCP specification, but may be the best choice if, say,
 669             the root filesystem relies on this connection. Defaults to
 670             false.</para>
 671           </listitem>
 672         </varlistentry>
 673         <varlistentry>
 674           <term><varname>ClientIdentifier=</varname></term>
 675           <listitem>
 676             <para>DHCP client identifier to use. Either <literal>mac</literal>
 677             to use the MAC address of the link or <literal>duid</literal>
 678             (the default) to use a RFC4361-compliant Client ID.</para>
 679           </listitem>
 680         </varlistentry>
 681         <varlistentry>
 682           <term><varname>VendorClassIdentifier=</varname></term>
 683           <listitem>
 684             <para>The vendor class identifier used to identify vendor
 685             type and configuration.</para>
 686           </listitem>
 687         </varlistentry>
 688         <varlistentry>
 689           <term><varname>RequestBroadcast=</varname></term>
 690           <listitem>
 691             <para>Request the server to use broadcast messages before
 692             the IP address has been configured. This is necessary for
 693             devices that cannot receive RAW packets, or that cannot
 694             receive packets at all before an IP address has been
 695             configured. On the other hand, this must not be enabled on
 696             networks where broadcasts are filtered out.</para>
 697           </listitem>
 698         </varlistentry>
 699         <varlistentry>
 700           <term><varname>RouteMetric=</varname></term>
 701           <listitem>
 702             <para>Set the routing metric for routes specified by the
 703             DHCP server.</para>
 704           </listitem>
 705         </varlistentry>
 706       </variablelist>
 707
 708   </refsect1>
 709
 710   <refsect1>
 711     <title>[DHCPServer] Section Options</title>
 712     <para>The <literal>[DHCPServer]</literal> section contains
 713     settings for the DHCP server, if enabled via the
 714     <varname>DHCPServer=</varname> option described above:</para>
 715
 716     <variablelist class='network-directives'>
 717
 718       <varlistentry>
 719         <term><varname>PoolOffset=</varname></term>
 720         <term><varname>PoolSize=</varname></term>
 721
 722         <listitem><para>Configures the pool of addresses to hand out. The pool
 723         is a contiguous sequence of IP addresses in the subnet configured for
 724         the server address, which does not include the subnet nor the broadcast
 725         address. <varname>PoolOffset=</varname> takes the offset of the pool
 726         from the start of subnet, or zero to use the default value.
 727         <varname>PoolSize=</varname> takes the number of IP addresses in the
 728         pool or zero to use the default value. By default, the pool starts at
 729         the first address after the subnet address and takes up the rest of
 730         the subnet, excluding the broadcast address. If the pool includes
 731         the server address (the default), this is reserved and not handed
 732         out to clients.</para></listitem>
 733       </varlistentry>
 734
 735       <varlistentry>
 736         <term><varname>DefaultLeaseTimeSec=</varname></term>
 737         <term><varname>MaxLeaseTimeSec=</varname></term>
 738
 739         <listitem><para>Control the default and maximum DHCP lease
 740         time to pass to clients. These settings take time values in seconds or
 741         another common time unit, depending on the suffix. The default
 742         lease time is used for clients that did not ask for a specific
 743         lease time. If a client asks for a lease time longer than the
 744         maximum lease time, it is automatically shortened to the
 745         specified time. The default lease time defaults to 1h, the
 746         maximum lease time to 12h. Shorter lease times are beneficial
 747         if the configuration data in DHCP leases changes frequently
 748         and clients shall learn the new settings with shorter
 749         latencies. Longer lease times reduce the generated DHCP
 750         network traffic.</para></listitem>
 751       </varlistentry>
 752
 753       <varlistentry>
 754         <term><varname>EmitDNS=</varname></term>
 755         <term><varname>DNS=</varname></term>
 756
 757         <listitem><para>Configures whether the DHCP leases handed out
 758         to clients shall contain DNS server information. The
 759         <varname>EmitDNS=</varname> setting takes a boolean argument
 760         and defaults to <literal>yes</literal>. The DNS servers to
 761         pass to clients may be configured with the
 762         <varname>DNS=</varname> option, which takes a list of IPv4
 763         addresses. If the <varname>EmitDNS=</varname> option is
 764         enabled but no servers configured, the servers are
 765         automatically propagated from an "uplink" interface that has
 766         appropriate servers set. The "uplink" interface is determined
 767         by the default route of the system with the highest
 768         priority. Note that this information is acquired at the time
 769         the lease is handed out, and does not take uplink interfaces
 770         into account that acquire DNS or NTP server information at a
 771         later point. DNS server propagation does not take
 772         <filename>/etc/resolv.conf</filename> into account. Also, note
 773         that the leases are not refreshed if the uplink network
 774         configuration changes. To ensure clients regularly acquire the
 775         most current uplink DNS server information, it is thus
 776         advisable to shorten the DHCP lease time via
 777         <varname>MaxLeaseTimeSec=</varname> described
 778         above.</para></listitem>
 779       </varlistentry>
 780
 781       <varlistentry>
 782         <term><varname>EmitNTP=</varname></term>
 783         <term><varname>NTP=</varname></term>
 784
 785         <listitem><para>Similar to the <varname>EmitDNS=</varname> and
 786         <varname>DNS=</varname> settings described above, these
 787         settings configure whether and what NTP server information
 788         shall be emitted as part of the DHCP lease. The same syntax,
 789         propagation semantics and defaults apply as for
 790         <varname>EmitDNS=</varname> and
 791         <varname>DNS=</varname>.</para></listitem>
 792       </varlistentry>
 793
 794       <varlistentry>
 795         <term><varname>EmitTimezone=</varname></term>
 796         <term><varname>Timezone=</varname></term>
 797
 798         <listitem><para>Configures whether the DHCP leases handed out
 799         to clients shall contain timezone information. The
 800         <varname>EmitTimezone=</varname> setting takes a boolean
 801         argument and defaults to <literal>yes</literal>. The
 802         <varname>Timezone=</varname> setting takes a timezone string
 803         (such as <literal>Europe/Berlin</literal> or
 804         <literal>UTC</literal>) to pass to clients. If no explicit
 805         timezone is set, the system timezone of the local host is
 806         propagated, as determined by the
 807         <filename>/etc/localtime</filename> symlink.</para></listitem>
 808       </varlistentry>
 809
 810     </variablelist>
 811   </refsect1>
 812
 813   <refsect1>
 814     <title>[Bridge] Section Options</title>
 815       <para>The <literal>[Bridge]</literal> section accepts the
 816       following keys.</para>
 817       <variablelist class='network-directives'>
 818         <varlistentry>
 819           <term><varname>UnicastFlood=</varname></term>
 820           <listitem>
 821             <para>A boolean. Controls whether the bridge should flood
 822             traffic for which an FDB entry is missing and the destination
 823             is unknown through this port. Defaults to on.
 824             </para>
 825           </listitem>
 826         </varlistentry>
 827         <varlistentry>
 828           <term><varname>HairPin=</varname></term>
 829           <listitem>
 830             <para>A boolean. Configures whether traffic may be sent back
 831             out of the port on which it was received. By default, this
 832             flag is false, and the bridge will not forward traffic back
 833             out of the receiving port.</para>
 834           </listitem>
 835         </varlistentry>
 836         <varlistentry>
 837           <term><varname>UseBPDU=</varname></term>
 838           <listitem>
 839             <para>A boolean. Configures whether STP Bridge Protocol Data Units will be
 840             processed by the bridge port. Defaults to yes.</para>
 841           </listitem>
 842         </varlistentry>
 843         <varlistentry>
 844           <term><varname>FastLeave=</varname></term>
 845           <listitem>
 846             <para>A boolean. This flag allows the bridge to immediately stop multicast
 847             traffic on a port that receives an IGMP Leave message. It is only used with
 848             IGMP snooping if enabled on the bridge. Defaults to off.</para>
 849           </listitem>
 850         </varlistentry>
 851         <varlistentry>
 852           <term><varname>AllowPortToBeRoot=</varname></term>
 853           <listitem>
 854             <para>A boolean. Configures whether a given port is allowed to
 855             become a root port. Only used when STP is enabled on the bridge.
 856             Defaults to on.</para>
 857           </listitem>
 858         </varlistentry>
 859         <varlistentry>
 860           <term><varname>Cost=</varname></term>
 861           <listitem>
 862             <para>Sets the "cost" of sending packets of this interface.
 863             Each port in a bridge may have a different speed and the cost
 864             is used to decide which link to use. Faster interfaces
 865             should have lower costs.</para>
 866           </listitem>
 867         </varlistentry>
 868       </variablelist>
 869   </refsect1>
 870   <refsect1>
 871     <title>[BridgeFDB] Section Options</title>
 872       <para>The <literal>[BridgeFDB]</literal> section manages the
 873       forwarding database table of a port and accepts the following
 874       keys. Specify several <literal>[BridgeFDB]</literal> sections to
 875       configure several static MAC table entries.</para>
 876
 877       <variablelist class='network-directives'>
 878         <varlistentry>
 879           <term><varname>MACAddress=</varname></term>
 880           <listitem>
 881             <para>As in the <literal>[Network]</literal> section. This
 882             key is mandatory.</para>
 883           </listitem>
 884         </varlistentry>
 885         <varlistentry>
 886           <term><varname>VLANId=</varname></term>
 887           <listitem>
 888             <para>The VLAN ID for the new static MAC table entry. If
 889             omitted, no VLAN ID info is appended to the new static MAC
 890             table entry.</para>
 891           </listitem>
 892         </varlistentry>
 893       </variablelist>
 894   </refsect1>
 895
 896   <refsect1>
 897     <title>Example</title>
 898     <example>
 899       <title>/etc/systemd/network/50-static.network</title>
 900
 901       <programlisting>[Match]
 902 Name=enp2s0
 903
 904 [Network]
 905 Address=192.168.0.15/24
 906 Gateway=192.168.0.1</programlisting>
 907     </example>
 908
 909     <example>
 910       <title>/etc/systemd/network/80-dhcp.network</title>
 911
 912       <programlisting>[Match]
 913 Name=en*
 914
 915 [Network]
 916 DHCP=yes</programlisting>
 917     </example>
 918
 919     <example>
 920       <title>/etc/systemd/network/25-bridge-static.network</title>
 921
 922       <programlisting>[Match]
 923 Name=bridge0
 924
 925 [Network]
 926 Address=192.168.0.15/24
 927 Gateway=192.168.0.1
 928 DNS=192.168.0.1</programlisting>
 929     </example>
 930
 931     <example>
 932       <title>/etc/systemd/network/25-bridge-slave-interface.network</title>
 933
 934       <programlisting>[Match]
 935 Name=enp2s0
 936
 937 [Network]
 938 Bridge=bridge0</programlisting>
 939     </example>
 940     <example>
 941       <title>/etc/systemd/network/25-ipip.network</title>
 942
 943       <programlisting>[Match]
 944 Name=em1
 945
 946 [Network]
 947 Tunnel=ipip-tun</programlisting>
 948     </example>
 949
 950     <example>
 951       <title>/etc/systemd/network/25-sit.network</title>
 952
 953       <programlisting>[Match]
 954 Name=em1
 955
 956 [Network]
 957 Tunnel=sit-tun</programlisting>
 958     </example>
 959
 960     <example>
 961       <title>/etc/systemd/network/25-gre.network</title>
 962
 963       <programlisting>[Match]
 964 Name=em1
 965
 966 [Network]
 967 Tunnel=gre-tun</programlisting>
 968     </example>
 969
 970     <example>
 971       <title>/etc/systemd/network/25-vti.network</title>
 972
 973       <programlisting>[Match]
 974 Name=em1
 975
 976 [Network]
 977 Tunnel=vti-tun</programlisting>
 978     </example>
 979
 980     <example>
 981       <title>/etc/systemd/network/25-bond.network</title>
 982
 983       <programlisting>[Match]
 984 Name=bond1
 985
 986 [Network]
 987 DHCP=yes
 988 </programlisting>
 989     </example>
 990
 991   </refsect1>
 992
 993   <refsect1>
 994     <title>See Also</title>
 995     <para>
 996       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 997       <citerefentry><refentrytitle>systemd-networkd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 998       <citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 999       <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1000     </para>
1001   </refsect1>
1002
1003 </refentry>