man/systemd.network.xml

   1 <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   This file is part of systemd.
   7
   8   Copyright 2013 Tom Gundersen
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
  14
  15   systemd is distributed in the hope that it will be useful, but
  16   WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   Lesser General Public License for more details.
  19
  20   You should have received a copy of the GNU Lesser General Public License
  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22 -->
  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 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 bits 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>Bridge=</varname></term>
 412           <listitem>
 413             <para>The name of the bridge to add the link to.</para>
 414           </listitem>
 415         </varlistentry>
 416         <varlistentry>
 417           <term><varname>Bond=</varname></term>
 418           <listitem>
 419             <para>The name of the bond to add the link to.</para>
 420           </listitem>
 421         </varlistentry>
 422         <varlistentry>
 423           <term><varname>VLAN=</varname></term>
 424           <listitem>
 425             <para>The name of a VLAN to create on the link. This
 426             option may be specified more than once.</para>
 427           </listitem>
 428         </varlistentry>
 429         <varlistentry>
 430           <term><varname>MACVLAN=</varname></term>
 431           <listitem>
 432             <para>The name of a MACVLAN to create on the link. This
 433             option may be specified more than once.</para>
 434           </listitem>
 435         </varlistentry>
 436         <varlistentry>
 437           <term><varname>VXLAN=</varname></term>
 438           <listitem>
 439             <para>The name of a VXLAN to create on the link. This
 440             option may be specified more than once.</para>
 441           </listitem>
 442         </varlistentry>
 443         <varlistentry>
 444           <term><varname>Tunnel=</varname></term>
 445           <listitem>
 446             <para>The name of a Tunnel to create on the link. This
 447             option may be specified more than once.</para>
 448           </listitem>
 449         </varlistentry>
 450       </variablelist>
 451
 452   </refsect1>
 453
 454   <refsect1>
 455     <title>[Address] Section Options</title>
 456
 457       <para>An <literal>[Address]</literal> section accepts the
 458       following keys. Specify several <literal>[Address]</literal>
 459       sections to configure several addresses.</para>
 460
 461       <variablelist class='network-directives'>
 462         <varlistentry>
 463           <term><varname>Address=</varname></term>
 464           <listitem>
 465             <para>As in the <literal>[Network]</literal> section. This
 466             key is mandatory.</para>
 467           </listitem>
 468         </varlistentry>
 469         <varlistentry>
 470           <term><varname>Peer=</varname></term>
 471           <listitem>
 472             <para>The peer address in a point-to-point connection.
 473             Accepts the same format as the <literal>Address</literal>
 474             key.</para>
 475           </listitem>
 476         </varlistentry>
 477         <varlistentry>
 478           <term><varname>Broadcast=</varname></term>
 479           <listitem>
 480             <para>The broadcast address, which must be in the format
 481             described in
 482             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 483             This key only applies to IPv4 addresses. If it is not
 484             given, it is derived from the <literal>Address</literal>
 485             key.</para>
 486           </listitem>
 487         </varlistentry>
 488         <varlistentry>
 489           <term><varname>Label=</varname></term>
 490           <listitem>
 491             <para>An address label.</para>
 492           </listitem>
 493         </varlistentry>
 494       </variablelist>
 495   </refsect1>
 496
 497   <refsect1>
 498     <title>[Route] Section Options</title>
 499       <para>The <literal>[Route]</literal> section accepts the
 500       following keys. Specify several <literal>[Route]</literal>
 501       sections to configure several routes.</para>
 502
 503       <variablelist class='network-directives'>
 504         <varlistentry>
 505           <term><varname>Gateway=</varname></term>
 506           <listitem>
 507             <para>As in the <literal>[Network]</literal> section.</para>
 508           </listitem>
 509         </varlistentry>
 510         <varlistentry>
 511           <term><varname>Destination=</varname></term>
 512           <listitem>
 513             <para>The destination prefix of the route. Possibly
 514             followed by a slash and the prefixlength. If omitted, a
 515             full-length host route is assumed.</para>
 516           </listitem>
 517         </varlistentry>
 518         <varlistentry>
 519           <term><varname>Source=</varname></term>
 520           <listitem>
 521             <para>The source prefix of the route. Possibly followed by
 522             a slash and the prefixlength. If omitted, a full-length
 523             host route is assumed.</para>
 524           </listitem>
 525         </varlistentry>
 526         <varlistentry>
 527           <term><varname>Metric=</varname></term>
 528           <listitem>
 529             <para>The metric of the route. An unsigned integer</para>
 530           </listitem>
 531         </varlistentry>
 532         <varlistentry>
 533           <term><varname>Scope=</varname></term>
 534           <listitem>
 535             <para>The scope of the route. One of the values <literal>global</literal>,
 536             <literal>link</literal> or <literal>host</literal>. Defaults to
 537             <literal>global</literal>.</para>
 538           </listitem>
 539         </varlistentry>
 540       </variablelist>
 541   </refsect1>
 542
 543   <refsect1>
 544     <title>[DHCP] Section Options</title>
 545       <para>The <literal>[DHCP]</literal> section configures the
 546       DHCPv4 and DHCP6 client, if it is enabled with the
 547       <varname>DHCP=</varname> setting described above:</para>
 548
 549       <variablelist class='network-directives'>
 550         <varlistentry>
 551           <term><varname>UseDNS=</varname></term>
 552           <listitem>
 553             <para>When true (the default), the DNS servers received
 554             from the DHCP server will be used and take precedence over
 555             any statically configured ones.</para>
 556
 557             <para>This corresponds to the <option>nameserver</option>
 558             option in <citerefentry
 559             project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 560           </listitem>
 561         </varlistentry>
 562         <varlistentry>
 563           <term><varname>UseNTP=</varname></term>
 564           <listitem>
 565             <para>When true (the default), the NTP servers received
 566             from the DHCP server will be used by systemd-timesyncd
 567             and take precedence over any statically configured ones.</para>
 568           </listitem>
 569         </varlistentry>
 570         <varlistentry>
 571           <term><varname>UseMTU=</varname></term>
 572           <listitem>
 573             <para>When true, the interface maximum transmission unit
 574             from the DHCP server will be used on the current link.
 575             Defaults to false.</para>
 576           </listitem>
 577         </varlistentry>
 578         <varlistentry>
 579           <term><varname>SendHostname=</varname></term>
 580           <listitem>
 581             <para>When true (the default), the machine's hostname will
 582             be sent to the DHCP server.</para>
 583           </listitem>
 584         </varlistentry>
 585         <varlistentry>
 586           <term><varname>UseHostname=</varname></term>
 587           <listitem>
 588             <para>When true (the default), the hostname received from
 589             the DHCP server will be set as the transient hostname of the system
 590             </para>
 591           </listitem>
 592         </varlistentry>
 593         <varlistentry>
 594         <term><varname>Hostname=</varname></term>
 595         <listitem>
 596           <para>Use this value for the hostname which is sent to the
 597           DHCP server, instead of machine's hostname.</para>
 598         </listitem>
 599       </varlistentry>
 600         <varlistentry>
 601           <term><varname>UseDomains=</varname></term>
 602           <listitem>
 603             <para>When true (not the default), the domain name
 604             received from the DHCP server will be used for DNS
 605             resolution over this link. When a name cannot be resolved
 606             as specified, the domain name will be used a suffix and
 607             name resolution of that will be attempted.</para>
 608
 609             <para>This corresponds to the <option>domain</option>
 610             option in <citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 611             and should not be enabled on untrusted networks.</para>
 612           </listitem>
 613         </varlistentry>
 614         <varlistentry>
 615           <term><varname>UseRoutes=</varname></term>
 616           <listitem>
 617             <para>When true (the default), the static routes will be
 618             requested from the DHCP server and added to the routing
 619             table with metric of 1024.</para>
 620           </listitem>
 621         </varlistentry>
 622
 623         <varlistentry>
 624           <term><varname>UseTimezone=</varname></term>
 625
 626           <listitem><para>When true, the timezone received from the
 627           DHCP server will be set as as timezone of the local
 628           system. Defaults to <literal>no</literal>.</para></listitem>
 629         </varlistentry>
 630
 631         <varlistentry>
 632           <term><varname>CriticalConnection=</varname></term>
 633           <listitem>
 634             <para>When true, the connection will never be torn down
 635             even if the DHCP lease expires. This is contrary to the
 636             DHCP specification, but may be the best choice if, say,
 637             the root filesystem relies on this connection. Defaults to
 638             false.</para>
 639           </listitem>
 640         </varlistentry>
 641         <varlistentry>
 642           <term><varname>ClientIdentifier=</varname></term>
 643           <listitem>
 644             <para>DHCP client identifier to use. Either <literal>mac</literal>
 645             to use the MAC address of the link or <literal>duid</literal>
 646             (the default) to use a RFC4361-compliant Client ID.</para>
 647           </listitem>
 648         </varlistentry>
 649         <varlistentry>
 650           <term><varname>VendorClassIdentifier=</varname></term>
 651           <listitem>
 652             <para>The vendor class identifier used to identify vendor
 653             type and configuration.</para>
 654           </listitem>
 655         </varlistentry>
 656         <varlistentry>
 657           <term><varname>RequestBroadcast=</varname></term>
 658           <listitem>
 659             <para>Request the server to use broadcast messages before
 660             the IP address has been configured. This is necessary for
 661             devices that cannot receive RAW packets, or that cannot
 662             receive packets at all before an IP address has been
 663             configured. On the other hand, this must not be enabled on
 664             networks where broadcasts are filtered out.</para>
 665           </listitem>
 666         </varlistentry>
 667         <varlistentry>
 668           <term><varname>RouteMetric=</varname></term>
 669           <listitem>
 670             <para>Set the routing metric for routes specified by the
 671             DHCP server.</para>
 672           </listitem>
 673         </varlistentry>
 674       </variablelist>
 675
 676   </refsect1>
 677
 678   <refsect1>
 679     <title>[DHCPServer] Section Options</title>
 680     <para>The <literal>[DHCPServer]</literal> section contains
 681     settings for the DHCP server, if enabled via the
 682     <varname>DHCPServer=</varname> option described above:</para>
 683
 684     <variablelist class='network-directives'>
 685
 686       <varlistentry>
 687         <term><varname>PoolOffset=</varname></term>
 688         <term><varname>PoolSize=</varname></term>
 689
 690         <listitem><para>Configures the pool of addresses to hand out. The pool
 691         is a contiguous sequence of IP addresses in the subnet configured for
 692         the server address, which does not include the subnet nor the broadcast
 693         address. <varname>PoolOffset=</varname> takes the offset of the pool
 694         from the start of subnet, or zero to use the default value.
 695         <varname>PoolSize=</varname> takes the number of IP addresses in the
 696         pool or zero to use the default value. By default the pool starts at
 697         the first address after the subnet address and takes up the rest of
 698         the subnet, excluding the broadcast address. If the pool includes
 699         the server address (the default), this is reserved and not handed
 700         out to clients.</para></listitem>
 701       </varlistentry>
 702
 703       <varlistentry>
 704         <term><varname>DefaultLeaseTimeSec=</varname></term>
 705         <term><varname>MaxLeaseTimeSec=</varname></term>
 706
 707         <listitem><para>Control the default and maximum DHCP lease
 708         time to pass to clients. These settings take time values in seconds or
 709         another common time unit, depending on the suffix. The default
 710         lease time is used for clients that did not ask for a specific
 711         lease time. If a client asks for a lease time longer than the
 712         maximum lease time it is automatically shortened to the
 713         specified time. The default lease time defaults to 1h, the
 714         maximum lease time to 12h. Shorter lease times are beneficial
 715         if the configuration data in DHCP leases changes frequently
 716         and clients shall learn the new settings with shorter
 717         latencies. Longer lease times reduce the generated DHCP
 718         network traffic.</para></listitem>
 719       </varlistentry>
 720
 721       <varlistentry>
 722         <term><varname>EmitDNS=</varname></term>
 723         <term><varname>DNS=</varname></term>
 724
 725         <listitem><para>Configures whether the DHCP leases handed out
 726         to clients shall contain DNS server information. The
 727         <varname>EmitDNS=</varname> setting takes a boolean argument
 728         and defaults to <literal>yes</literal>. The DNS servers to
 729         pass to clients may be configured with the
 730         <varname>DNS=</varname> option, which takes a list of IPv4
 731         addresses. If the <varname>EmitDNS=</varname> option is
 732         enabled but no servers configured the servers are
 733         automatically propagated from an "uplink" interface that has
 734         appropriate servers set. The "uplink" interface is determined
 735         by the default route of the system with the highest
 736         priority. Note that this information is acquired at the time
 737         the lease is handed out, and does not take uplink interfaces
 738         into account that acquire DNS or NTP server information at a
 739         later point. DNS server propagation does not take
 740         <filename>/etc/resolv.conf</filename> into account. Also, note
 741         that the leases are not refreshed if uplink network
 742         configuration changes. To ensure clients regularly acquire the
 743         most current uplink DNS server information it is thus
 744         advisable to shorten the DHCP lease time via
 745         <varname>MaxLeaseTimeSec=</varname> described
 746         above.</para></listitem>
 747       </varlistentry>
 748
 749       <varlistentry>
 750         <term><varname>EmitNTP=</varname></term>
 751         <term><varname>NTP=</varname></term>
 752
 753         <listitem><para>Similar to the <varname>EmitDNS=</varname> and
 754         <varname>DNS=</varname> settings described above these
 755         settings configure whether and what NTP server information
 756         shall be emitted as part of the DHCP lease. The same syntax,
 757         propagation semantics and defaults apply as for
 758         <varname>EmitDNS=</varname> and
 759         <varname>DNS=</varname>.</para></listitem>
 760       </varlistentry>
 761
 762       <varlistentry>
 763         <term><varname>EmitTimezone=</varname></term>
 764         <term><varname>Timezone=</varname></term>
 765
 766         <listitem><para>Configures whether the DHCP leases handed out
 767         to clients shall contain timezone information. The
 768         <varname>EmitTimezone=</varname> setting takes a boolean
 769         argument and defaults to <literal>yes</literal>. The
 770         <varname>Timezone=</varname> setting takes a timezone string
 771         (such as <literal>Europe/Berlin</literal> or
 772         <literal>UTC</literal>) to pass to clients. If no explicit
 773         timezone is set the system timezone of the local host is
 774         propagated, as determined by the
 775         <filename>/etc/localtime</filename> symlink.</para></listitem>
 776       </varlistentry>
 777
 778     </variablelist>
 779   </refsect1>
 780
 781   <refsect1>
 782     <title>[Bridge] Section Options</title>
 783       <para>The <literal>[Bridge]</literal> section accepts the
 784       following keys.</para>
 785       <variablelist class='network-directives'>
 786         <varlistentry>
 787           <term><varname>UnicastFlood=</varname></term>
 788           <listitem>
 789             <para>A boolean. Controls whether the bridge should flood
 790             traffic for which an FDB entry is missing and the destination
 791             is unknown through this port. Defaults to on.
 792             </para>
 793           </listitem>
 794         </varlistentry>
 795         <varlistentry>
 796           <term><varname>HairPin=</varname></term>
 797           <listitem>
 798             <para>A boolean. Configures whether traffic may be sent back
 799             out of the port on which it was received. By default, this
 800             flag is false, and the bridge will not forward traffic back
 801             out of the receiving port.</para>
 802           </listitem>
 803         </varlistentry>
 804         <varlistentry>
 805           <term><varname>UseBPDU=</varname></term>
 806           <listitem>
 807             <para>A boolean. Configures whether STP Bridge Protocol Data Units will be
 808             processed by the bridge port. Defaults to yes.</para>
 809           </listitem>
 810         </varlistentry>
 811         <varlistentry>
 812           <term><varname>FastLeave=</varname></term>
 813           <listitem>
 814             <para>A boolean. This flag allows the bridge to immediately stop multicast
 815             traffic on a port that receives IGMP Leave message. It is only used with
 816             IGMP snooping if enabled on the bridge. Defaults to off.</para>
 817           </listitem>
 818         </varlistentry>
 819         <varlistentry>
 820           <term><varname>AllowPortToBeRoot=</varname></term>
 821           <listitem>
 822             <para>A boolean. Configures whether a given port is allowed to
 823             become a root port. Only used when STP is enabled on the bridge.
 824             Defaults to on.</para>
 825           </listitem>
 826         </varlistentry>
 827         <varlistentry>
 828           <term><varname>Cost=</varname></term>
 829           <listitem>
 830             <para>Sets the "cost" of sending packets of this interface.
 831             Each port in a bridge may have different speed and the cost
 832             is used to decide which link to use. Faster interfaces
 833             should have lower costs.</para>
 834           </listitem>
 835         </varlistentry>
 836       </variablelist>
 837   </refsect1>
 838   <refsect1>
 839     <title>[BridgeFDB] Section Options</title>
 840       <para>The <literal>[BridgeFDB]</literal> section manages the
 841       forwarding database table of a port and accepts the following
 842       keys. Specify several <literal>[BridgeFDB]</literal> sections to
 843       configure several static MAC table entries.</para>
 844
 845       <variablelist class='network-directives'>
 846         <varlistentry>
 847           <term><varname>MACAddress=</varname></term>
 848           <listitem>
 849             <para>As in the <literal>[Network]</literal> section. This
 850             key is mandatory.</para>
 851           </listitem>
 852         </varlistentry>
 853         <varlistentry>
 854           <term><varname>VLANId=</varname></term>
 855           <listitem>
 856             <para>The VLAN Id for the new static MAC table entry. If
 857             omitted, no VLAN Id info is appended to the new static MAC
 858             table entry.</para>
 859           </listitem>
 860         </varlistentry>
 861       </variablelist>
 862   </refsect1>
 863
 864   <refsect1>
 865     <title>Example</title>
 866     <example>
 867       <title>/etc/systemd/network/50-static.network</title>
 868
 869       <programlisting>[Match]
 870 Name=enp2s0
 871
 872 [Network]
 873 Address=192.168.0.15/24
 874 Gateway=192.168.0.1</programlisting>
 875     </example>
 876
 877     <example>
 878       <title>/etc/systemd/network/80-dhcp.network</title>
 879
 880       <programlisting>[Match]
 881 Name=en*
 882
 883 [Network]
 884 DHCP=yes</programlisting>
 885     </example>
 886
 887     <example>
 888       <title>/etc/systemd/network/bridge-static.network</title>
 889
 890       <programlisting>[Match]
 891 Name=bridge0
 892
 893 [Network]
 894 Address=192.168.0.15/24
 895 Gateway=192.168.0.1
 896 DNS=192.168.0.1</programlisting>
 897     </example>
 898
 899     <example>
 900       <title>/etc/systemd/network/bridge-slave-interface.network</title>
 901
 902       <programlisting>[Match]
 903 Name=enp2s0
 904
 905 [Network]
 906 Bridge=bridge0</programlisting>
 907     </example>
 908     <example>
 909       <title>/etc/systemd/network/ipip.network</title>
 910
 911       <programlisting>[Match]
 912 Name=em1
 913
 914 [Network]
 915 Tunnel=ipip-tun</programlisting>
 916     </example>
 917
 918     <example>
 919       <title>/etc/systemd/network/sit.network</title>
 920
 921       <programlisting>[Match]
 922 Name=em1
 923
 924 [Network]
 925 Tunnel=sit-tun</programlisting>
 926     </example>
 927
 928     <example>
 929       <title>/etc/systemd/network/gre.network</title>
 930
 931       <programlisting>[Match]
 932 Name=em1
 933
 934 [Network]
 935 Tunnel=gre-tun</programlisting>
 936     </example>
 937
 938     <example>
 939       <title>/etc/systemd/network/vti.network</title>
 940
 941       <programlisting>[Match]
 942 Name=em1
 943
 944 [Network]
 945 Tunnel=vti-tun</programlisting>
 946     </example>
 947
 948     <example>
 949       <title>/etc/systemd/network/bond.network</title>
 950
 951       <programlisting>[Match]
 952 Name=bond1
 953
 954 [Network]
 955 DHCP=yes
 956 </programlisting>
 957     </example>
 958
 959   </refsect1>
 960
 961   <refsect1>
 962     <title>See Also</title>
 963     <para>
 964       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 965       <citerefentry><refentrytitle>systemd-networkd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 966       <citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 967       <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 968     </para>
 969   </refsect1>
 970
 971 </refentry>