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     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>Note that DHCPv6 will by default be triggered by Router
 231             Advertisment, if that is enabled, regardless of this parameter.
 232             By enabling DHCPv6 support explicitly, the DHCPv6 client will
 233             be started regardless of the presence of routers on the link,
 234             or what flags the routers pass. See
 235             <literal>IPv6AcceptRouterAdvertisements=</literal>.</para>
 236
 237             <para>Furthermore, note that by default the domain name
 238             specified through DHCP is not used for name resolution.
 239             See option <option>UseDomains=</option> below.</para>
 240           </listitem>
 241         </varlistentry>
 242         <varlistentry>
 243           <term><varname>DHCPServer=</varname></term>
 244           <listitem>
 245             <para>A boolean. Enables DHCPv4 server support. Defaults
 246             to <literal>no</literal>. Further settings for the DHCP
 247             server may be set in the <literal>[DHCPServer]</literal>
 248             section described below.</para>
 249           </listitem>
 250         </varlistentry>
 251         <varlistentry>
 252           <term><varname>LinkLocalAddressing=</varname></term>
 253           <listitem>
 254             <para>Enables link-local address autoconfiguration. Accepts
 255             <literal>yes</literal>, <literal>no</literal>,
 256             <literal>ipv4</literal>, or <literal>ipv6</literal>. Defaults to
 257             <literal>ipv6</literal>.</para>
 258           </listitem>
 259         </varlistentry>
 260         <varlistentry>
 261           <term><varname>IPv4LLRoute=</varname></term>
 262           <listitem>
 263             <para>A boolean. When true, sets up the route needed for
 264             non-IPv4LL hosts to communicate with IPv4LL-only hosts. Defaults
 265             to false.
 266             </para>
 267           </listitem>
 268         </varlistentry>
 269         <varlistentry>
 270           <term><varname>IPv6Token=</varname></term>
 271           <listitem>
 272             <para>An IPv6 address with the top 64 bits unset. When set, indicates the
 273             64-bit interface part of SLAAC IPv6 addresses for this link. By default,
 274             it is autogenerated.</para>
 275           </listitem>
 276         </varlistentry>
 277         <varlistentry>
 278           <term><varname>LLMNR=</varname></term>
 279           <listitem>
 280             <para>A boolean or <literal>resolve</literal>. When true, enables
 281             Link-Local Multicast Name Resolution on the link. When set to
 282             <literal>resolve</literal>, only resolution is enabled, but not
 283             announcement. Defaults to true.</para>
 284           </listitem>
 285         </varlistentry>
 286         <varlistentry>
 287           <term><varname>LLDP=</varname></term>
 288           <listitem>
 289             <para>A boolean. When true, enables LLDP link receive support.
 290             </para>
 291           </listitem>
 292         </varlistentry>
 293         <varlistentry>
 294           <term><varname>BindCarrier=</varname></term>
 295           <listitem>
 296             <para>A port or a list of ports. When set, controls the
 297             behavior of the current interface. When all ports in the list
 298             are in an operational down state, the current interface is brought
 299             down. When at least one port has carrier, the current interface
 300             is brought up.
 301             </para>
 302           </listitem>
 303         </varlistentry>
 304         <varlistentry>
 305           <term><varname>Address=</varname></term>
 306           <listitem>
 307             <para>A static IPv4 or IPv6 address and its prefix length,
 308             separated by a <literal>/</literal> character. Specify
 309             this key more than once to configure several addresses.
 310             The format of the address must be as described in
 311             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 312             This is a short-hand for an [Address] section only
 313             containing an Address key (see below). This option may be
 314             specified more than once.
 315             </para>
 316
 317             <para>If the specified address is 0.0.0.0 (for IPv4) or
 318             [::] (for IPv6), a new address range of the requested size
 319             is automatically allocated from a system-wide pool of
 320             unused ranges. The allocated range is checked against all
 321             current network interfaces and all known network
 322             configuration files to avoid address range conflicts. The
 323             default system-wide pool consists of 192.168.0.0/16,
 324             172.16.0.0/12 and 10.0.0.0/8 for IPv4, and fc00::/7 for
 325             IPv6. This functionality is useful to manage a large
 326             number of dynamically created network interfaces with the
 327             same network configuration and automatic address range
 328             assignment.</para>
 329
 330           </listitem>
 331         </varlistentry>
 332         <varlistentry>
 333           <term><varname>Gateway=</varname></term>
 334           <listitem>
 335             <para>The gateway address, which must be in the format
 336             described in
 337             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 338             This is a short-hand for a [Route] section only containing
 339             a Gateway key. This option may be specified more than
 340             once.</para>
 341           </listitem>
 342         </varlistentry>
 343         <varlistentry>
 344           <term><varname>DNS=</varname></term>
 345           <listitem>
 346             <para>A DNS server address, which must be in the format
 347             described in
 348             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 349             This option may be specified more than once.</para>
 350           </listitem>
 351         </varlistentry>
 352         <varlistentry>
 353           <term><varname>Domains=</varname></term>
 354           <listitem>
 355             <para>The domains used for DNS resolution over this link.</para>
 356           </listitem>
 357         </varlistentry>
 358         <varlistentry>
 359           <term><varname>NTP=</varname></term>
 360           <listitem>
 361             <para>An NTP server address. This option may be specified more than once.</para>
 362           </listitem>
 363         </varlistentry>
 364         <varlistentry>
 365           <term><varname>IPForward=</varname></term>
 366           <listitem><para>Configures IP forwarding for the network
 367           interface. If enabled, incoming packets on the network
 368           interface will be forwarded to other interfaces according to
 369           the routing table. Takes either a boolean argument, or the
 370           values <literal>ipv4</literal> or <literal>ipv6</literal>,
 371           which only enables IP forwarding for the specified address
 372           family, or <literal>kernel</literal>, which preserves existing sysctl settings.
 373           This controls the
 374           <filename>net.ipv4.conf.&lt;interface&gt;.forwarding</filename>
 375           and
 376           <filename>net.ipv6.conf.&lt;interface&gt;.forwarding</filename>
 377           sysctl options of the network interface (see <ulink
 378           url="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">ip-sysctl.txt</ulink>
 379           for details about sysctl options). Defaults to
 380           <literal>no</literal>.</para>
 381
 382          <para>Note: unless this option is turned on, or set to <literal>kernel</literal>,
 383           no IP forwarding is done on this interface, even if this is
 384           globally turned on in the kernel, with the
 385           <filename>net.ipv4.ip_forward</filename>,
 386           <filename>net.ipv4.conf.all.forwarding</filename>, and
 387           <filename>net.ipv6.conf.all.forwarding</filename> sysctl
 388           options.</para>
 389           </listitem>
 390         </varlistentry>
 391         <varlistentry>
 392           <term><varname>IPMasquerade=</varname></term>
 393           <listitem><para>Configures IP masquerading for the network
 394           interface. If enabled, packets forwarded from the network
 395           interface will be appear as coming from the local host.
 396           Takes a boolean argument. Implies
 397           <varname>IPForward=ipv4</varname>. Defaults to
 398           <literal>no</literal>.</para></listitem>
 399         </varlistentry>
 400         <varlistentry>
 401           <term><varname>IPv6PrivacyExtensions=</varname></term>
 402           <listitem><para>Configures use of stateless temporary
 403           addresses that change over time (see <ulink
 404           url="https://tools.ietf.org/html/rfc4941">RFC 4941</ulink>,
 405           Privacy Extensions for Stateless Address Autoconfiguration
 406           in IPv6). Takes a boolean or the special values
 407           <literal>prefer-public</literal> and
 408           <literal>kernel</literal>. When true, enables the privacy
 409           extensions and prefers temporary addresses over public
 410           addresses. When <literal>prefer-public</literal>, enables the
 411           privacy extensions, but prefers public addresses over
 412           temporary addresses. When false, the privacy extensions
 413           remain disabled. When <literal>kernel</literal>, the kernel's
 414           default setting will be left in place.  Defaults to
 415           <literal>no</literal>.</para></listitem>
 416         </varlistentry>
 417         <varlistentry>
 418           <term><varname>IPv6AcceptRouterAdvertisements=</varname></term>
 419           <listitem><para>Force the setting of the <filename>accept_ra</filename>
 420           (router advertisements) setting for the interface.
 421           When unset, the kernel default is used, and router
 422           advertisements are accepted only when local forwarding
 423           is disabled for that interface.
 424           When router advertisements are accepted, they will
 425           trigger the start of the DHCPv6 client if the relevant
 426           flags are passed, or if no routers are found on the link.
 427           Takes a boolean. If true, router advertisements are
 428           accepted, when false, router advertisements are ignored,
 429           independently of the local forwarding state.</para>
 430
 431           <para>See
 432           <ulink url="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">ip-sysctl.txt</ulink>
 433           in the kernel documentation, but note that systemd's
 434           setting of <constant>1</constant> corresponds to
 435           kernel's setting of <constant>2</constant>.</para>
 436         </listitem>
 437         </varlistentry>
 438         <varlistentry>
 439           <term><varname>IPv6DuplicateAddressDetection=</varname></term>
 440           <listitem><para>Configures the amount of IPv6 Duplicate
 441           Address Detection (DAD) probes to send. Defaults to unset.
 442         </para></listitem>
 443         </varlistentry>
 444         <varlistentry>
 445           <term><varname>IPv6HopLimit=</varname></term>
 446           <listitem><para>Configures IPv6 Hop Limit. For each router that
 447           forwards the packet, the hop limit is decremented by 1. When the
 448           hop limit field reaches zero, the packet is discarded.
 449           Defaults to unset.
 450         </para></listitem>
 451         </varlistentry>
 452         <varlistentry>
 453           <term><varname>Bridge=</varname></term>
 454           <listitem>
 455             <para>The name of the bridge to add the link to.</para>
 456           </listitem>
 457         </varlistentry>
 458         <varlistentry>
 459           <term><varname>Bond=</varname></term>
 460           <listitem>
 461             <para>The name of the bond to add the link to.</para>
 462           </listitem>
 463         </varlistentry>
 464         <varlistentry>
 465           <term><varname>VLAN=</varname></term>
 466           <listitem>
 467             <para>The name of a VLAN to create on the link. This
 468             option may be specified more than once.</para>
 469           </listitem>
 470         </varlistentry>
 471         <varlistentry>
 472           <term><varname>MACVLAN=</varname></term>
 473           <listitem>
 474             <para>The name of a MACVLAN to create on the link. This
 475             option may be specified more than once.</para>
 476           </listitem>
 477         </varlistentry>
 478         <varlistentry>
 479           <term><varname>VXLAN=</varname></term>
 480           <listitem>
 481             <para>The name of a VXLAN to create on the link. This
 482             option may be specified more than once.</para>
 483           </listitem>
 484         </varlistentry>
 485         <varlistentry>
 486           <term><varname>Tunnel=</varname></term>
 487           <listitem>
 488             <para>The name of a Tunnel to create on the link. This
 489             option may be specified more than once.</para>
 490           </listitem>
 491         </varlistentry>
 492       </variablelist>
 493
 494   </refsect1>
 495
 496   <refsect1>
 497     <title>[Address] Section Options</title>
 498
 499       <para>An <literal>[Address]</literal> section accepts the
 500       following keys. Specify several <literal>[Address]</literal>
 501       sections to configure several addresses.</para>
 502
 503       <variablelist class='network-directives'>
 504         <varlistentry>
 505           <term><varname>Address=</varname></term>
 506           <listitem>
 507             <para>As in the <literal>[Network]</literal> section. This
 508             key is mandatory.</para>
 509           </listitem>
 510         </varlistentry>
 511         <varlistentry>
 512           <term><varname>Peer=</varname></term>
 513           <listitem>
 514             <para>The peer address in a point-to-point connection.
 515             Accepts the same format as the <literal>Address</literal>
 516             key.</para>
 517           </listitem>
 518         </varlistentry>
 519         <varlistentry>
 520           <term><varname>Broadcast=</varname></term>
 521           <listitem>
 522             <para>The broadcast address, which must be in the format
 523             described in
 524             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 525             This key only applies to IPv4 addresses. If it is not
 526             given, it is derived from the <literal>Address</literal>
 527             key.</para>
 528           </listitem>
 529         </varlistentry>
 530         <varlistentry>
 531           <term><varname>Label=</varname></term>
 532           <listitem>
 533             <para>An address label.</para>
 534           </listitem>
 535         </varlistentry>
 536       </variablelist>
 537   </refsect1>
 538
 539   <refsect1>
 540     <title>[Route] Section Options</title>
 541       <para>The <literal>[Route]</literal> section accepts the
 542       following keys. Specify several <literal>[Route]</literal>
 543       sections to configure several routes.</para>
 544
 545       <variablelist class='network-directives'>
 546         <varlistentry>
 547           <term><varname>Gateway=</varname></term>
 548           <listitem>
 549             <para>As in the <literal>[Network]</literal> section.</para>
 550           </listitem>
 551         </varlistentry>
 552         <varlistentry>
 553           <term><varname>Destination=</varname></term>
 554           <listitem>
 555             <para>The destination prefix of the route. Possibly
 556             followed by a slash and the prefix length. If omitted, a
 557             full-length host route is assumed.</para>
 558           </listitem>
 559         </varlistentry>
 560         <varlistentry>
 561           <term><varname>Source=</varname></term>
 562           <listitem>
 563             <para>The source prefix of the route. Possibly followed by
 564             a slash and the prefix length. If omitted, a full-length
 565             host route is assumed.</para>
 566           </listitem>
 567         </varlistentry>
 568         <varlistentry>
 569           <term><varname>Metric=</varname></term>
 570           <listitem>
 571             <para>The metric of the route (an unsigned integer).</para>
 572           </listitem>
 573         </varlistentry>
 574         <varlistentry>
 575           <term><varname>Scope=</varname></term>
 576           <listitem>
 577             <para>The scope of the route, which can be <literal>global</literal>,
 578             <literal>link</literal> or <literal>host</literal>. Defaults to
 579             <literal>global</literal>.</para>
 580           </listitem>
 581         </varlistentry>
 582         <varlistentry>
 583           <term><varname>PreferredSource=</varname></term>
 584           <listitem>
 585             <para>The preferred source address of the route. The address
 586             must be in the format described in
 587             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
 588           </listitem>
 589         </varlistentry>
 590       </variablelist>
 591   </refsect1>
 592
 593   <refsect1>
 594     <title>[DHCP] Section Options</title>
 595       <para>The <literal>[DHCP]</literal> section configures the
 596       DHCPv4 and DHCP6 client, if it is enabled with the
 597       <varname>DHCP=</varname> setting described above:</para>
 598
 599       <variablelist class='network-directives'>
 600         <varlistentry>
 601           <term><varname>UseDNS=</varname></term>
 602           <listitem>
 603             <para>When true (the default), the DNS servers received
 604             from the DHCP server will be used and take precedence over
 605             any statically configured ones.</para>
 606
 607             <para>This corresponds to the <option>nameserver</option>
 608             option in <citerefentry
 609             project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 610           </listitem>
 611         </varlistentry>
 612         <varlistentry>
 613           <term><varname>UseNTP=</varname></term>
 614           <listitem>
 615             <para>When true (the default), the NTP servers received
 616             from the DHCP server will be used by systemd-timesyncd
 617             and take precedence over any statically configured ones.</para>
 618           </listitem>
 619         </varlistentry>
 620         <varlistentry>
 621           <term><varname>UseMTU=</varname></term>
 622           <listitem>
 623             <para>When true, the interface maximum transmission unit
 624             from the DHCP server will be used on the current link.
 625             Defaults to false.</para>
 626           </listitem>
 627         </varlistentry>
 628         <varlistentry>
 629           <term><varname>SendHostname=</varname></term>
 630           <listitem>
 631             <para>When true (the default), the machine's hostname will
 632             be sent to the DHCP server.</para>
 633           </listitem>
 634         </varlistentry>
 635         <varlistentry>
 636           <term><varname>UseHostname=</varname></term>
 637           <listitem>
 638             <para>When true (the default), the hostname received from
 639             the DHCP server will be set as the transient hostname of the system
 640             </para>
 641           </listitem>
 642         </varlistentry>
 643         <varlistentry>
 644         <term><varname>Hostname=</varname></term>
 645         <listitem>
 646           <para>Use this value for the hostname which is sent to the
 647           DHCP server, instead of machine's hostname.</para>
 648         </listitem>
 649       </varlistentry>
 650         <varlistentry>
 651           <term><varname>UseDomains=</varname></term>
 652           <listitem>
 653             <para>When true (not the default), the domain name
 654             received from the DHCP server will be used for DNS
 655             resolution over this link. When a name cannot be resolved
 656             as specified, the domain name will be used a suffix and
 657             name resolution of that will be attempted.</para>
 658
 659             <para>This corresponds to the <option>domain</option>
 660             option in <citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 661             and should not be enabled on untrusted networks.</para>
 662           </listitem>
 663         </varlistentry>
 664         <varlistentry>
 665           <term><varname>UseRoutes=</varname></term>
 666           <listitem>
 667             <para>When true (the default), the static routes will be
 668             requested from the DHCP server and added to the routing
 669             table with a metric of 1024.</para>
 670           </listitem>
 671         </varlistentry>
 672
 673         <varlistentry>
 674           <term><varname>UseTimezone=</varname></term>
 675
 676           <listitem><para>When true, the timezone received from the
 677           DHCP server will be set as as timezone of the local
 678           system. Defaults to <literal>no</literal>.</para></listitem>
 679         </varlistentry>
 680
 681         <varlistentry>
 682           <term><varname>CriticalConnection=</varname></term>
 683           <listitem>
 684             <para>When true, the connection will never be torn down
 685             even if the DHCP lease expires. This is contrary to the
 686             DHCP specification, but may be the best choice if, say,
 687             the root filesystem relies on this connection. Defaults to
 688             false.</para>
 689           </listitem>
 690         </varlistentry>
 691         <varlistentry>
 692           <term><varname>ClientIdentifier=</varname></term>
 693           <listitem>
 694             <para>DHCP client identifier to use. Either <literal>mac</literal>
 695             to use the MAC address of the link or <literal>duid</literal>
 696             (the default) to use a RFC4361-compliant Client ID.</para>
 697           </listitem>
 698         </varlistentry>
 699         <varlistentry>
 700           <term><varname>VendorClassIdentifier=</varname></term>
 701           <listitem>
 702             <para>The vendor class identifier used to identify vendor
 703             type and configuration.</para>
 704           </listitem>
 705         </varlistentry>
 706         <varlistentry>
 707           <term><varname>RequestBroadcast=</varname></term>
 708           <listitem>
 709             <para>Request the server to use broadcast messages before
 710             the IP address has been configured. This is necessary for
 711             devices that cannot receive RAW packets, or that cannot
 712             receive packets at all before an IP address has been
 713             configured. On the other hand, this must not be enabled on
 714             networks where broadcasts are filtered out.</para>
 715           </listitem>
 716         </varlistentry>
 717         <varlistentry>
 718           <term><varname>RouteMetric=</varname></term>
 719           <listitem>
 720             <para>Set the routing metric for routes specified by the
 721             DHCP server.</para>
 722           </listitem>
 723         </varlistentry>
 724       </variablelist>
 725
 726   </refsect1>
 727
 728   <refsect1>
 729     <title>[DHCPServer] Section Options</title>
 730     <para>The <literal>[DHCPServer]</literal> section contains
 731     settings for the DHCP server, if enabled via the
 732     <varname>DHCPServer=</varname> option described above:</para>
 733
 734     <variablelist class='network-directives'>
 735
 736       <varlistentry>
 737         <term><varname>PoolOffset=</varname></term>
 738         <term><varname>PoolSize=</varname></term>
 739
 740         <listitem><para>Configures the pool of addresses to hand out. The pool
 741         is a contiguous sequence of IP addresses in the subnet configured for
 742         the server address, which does not include the subnet nor the broadcast
 743         address. <varname>PoolOffset=</varname> takes the offset of the pool
 744         from the start of subnet, or zero to use the default value.
 745         <varname>PoolSize=</varname> takes the number of IP addresses in the
 746         pool or zero to use the default value. By default, the pool starts at
 747         the first address after the subnet address and takes up the rest of
 748         the subnet, excluding the broadcast address. If the pool includes
 749         the server address (the default), this is reserved and not handed
 750         out to clients.</para></listitem>
 751       </varlistentry>
 752
 753       <varlistentry>
 754         <term><varname>DefaultLeaseTimeSec=</varname></term>
 755         <term><varname>MaxLeaseTimeSec=</varname></term>
 756
 757         <listitem><para>Control the default and maximum DHCP lease
 758         time to pass to clients. These settings take time values in seconds or
 759         another common time unit, depending on the suffix. The default
 760         lease time is used for clients that did not ask for a specific
 761         lease time. If a client asks for a lease time longer than the
 762         maximum lease time, it is automatically shortened to the
 763         specified time. The default lease time defaults to 1h, the
 764         maximum lease time to 12h. Shorter lease times are beneficial
 765         if the configuration data in DHCP leases changes frequently
 766         and clients shall learn the new settings with shorter
 767         latencies. Longer lease times reduce the generated DHCP
 768         network traffic.</para></listitem>
 769       </varlistentry>
 770
 771       <varlistentry>
 772         <term><varname>EmitDNS=</varname></term>
 773         <term><varname>DNS=</varname></term>
 774
 775         <listitem><para>Configures whether the DHCP leases handed out
 776         to clients shall contain DNS server information. The
 777         <varname>EmitDNS=</varname> setting takes a boolean argument
 778         and defaults to <literal>yes</literal>. The DNS servers to
 779         pass to clients may be configured with the
 780         <varname>DNS=</varname> option, which takes a list of IPv4
 781         addresses. If the <varname>EmitDNS=</varname> option is
 782         enabled but no servers configured, the servers are
 783         automatically propagated from an "uplink" interface that has
 784         appropriate servers set. The "uplink" interface is determined
 785         by the default route of the system with the highest
 786         priority. Note that this information is acquired at the time
 787         the lease is handed out, and does not take uplink interfaces
 788         into account that acquire DNS or NTP server information at a
 789         later point. DNS server propagation does not take
 790         <filename>/etc/resolv.conf</filename> into account. Also, note
 791         that the leases are not refreshed if the uplink network
 792         configuration changes. To ensure clients regularly acquire the
 793         most current uplink DNS server information, it is thus
 794         advisable to shorten the DHCP lease time via
 795         <varname>MaxLeaseTimeSec=</varname> described
 796         above.</para></listitem>
 797       </varlistentry>
 798
 799       <varlistentry>
 800         <term><varname>EmitNTP=</varname></term>
 801         <term><varname>NTP=</varname></term>
 802
 803         <listitem><para>Similar to the <varname>EmitDNS=</varname> and
 804         <varname>DNS=</varname> settings described above, these
 805         settings configure whether and what NTP server information
 806         shall be emitted as part of the DHCP lease. The same syntax,
 807         propagation semantics and defaults apply as for
 808         <varname>EmitDNS=</varname> and
 809         <varname>DNS=</varname>.</para></listitem>
 810       </varlistentry>
 811
 812       <varlistentry>
 813         <term><varname>EmitTimezone=</varname></term>
 814         <term><varname>Timezone=</varname></term>
 815
 816         <listitem><para>Configures whether the DHCP leases handed out
 817         to clients shall contain timezone information. The
 818         <varname>EmitTimezone=</varname> setting takes a boolean
 819         argument and defaults to <literal>yes</literal>. The
 820         <varname>Timezone=</varname> setting takes a timezone string
 821         (such as <literal>Europe/Berlin</literal> or
 822         <literal>UTC</literal>) to pass to clients. If no explicit
 823         timezone is set, the system timezone of the local host is
 824         propagated, as determined by the
 825         <filename>/etc/localtime</filename> symlink.</para></listitem>
 826       </varlistentry>
 827
 828     </variablelist>
 829   </refsect1>
 830
 831   <refsect1>
 832     <title>[Bridge] Section Options</title>
 833       <para>The <literal>[Bridge]</literal> section accepts the
 834       following keys.</para>
 835       <variablelist class='network-directives'>
 836         <varlistentry>
 837           <term><varname>UnicastFlood=</varname></term>
 838           <listitem>
 839             <para>A boolean. Controls whether the bridge should flood
 840             traffic for which an FDB entry is missing and the destination
 841             is unknown through this port. Defaults to on.
 842             </para>
 843           </listitem>
 844         </varlistentry>
 845         <varlistentry>
 846           <term><varname>HairPin=</varname></term>
 847           <listitem>
 848             <para>A boolean. Configures whether traffic may be sent back
 849             out of the port on which it was received. By default, this
 850             flag is false, and the bridge will not forward traffic back
 851             out of the receiving port.</para>
 852           </listitem>
 853         </varlistentry>
 854         <varlistentry>
 855           <term><varname>UseBPDU=</varname></term>
 856           <listitem>
 857             <para>A boolean. Configures whether STP Bridge Protocol Data Units will be
 858             processed by the bridge port. Defaults to yes.</para>
 859           </listitem>
 860         </varlistentry>
 861         <varlistentry>
 862           <term><varname>FastLeave=</varname></term>
 863           <listitem>
 864             <para>A boolean. This flag allows the bridge to immediately stop multicast
 865             traffic on a port that receives an IGMP Leave message. It is only used with
 866             IGMP snooping if enabled on the bridge. Defaults to off.</para>
 867           </listitem>
 868         </varlistentry>
 869         <varlistentry>
 870           <term><varname>AllowPortToBeRoot=</varname></term>
 871           <listitem>
 872             <para>A boolean. Configures whether a given port is allowed to
 873             become a root port. Only used when STP is enabled on the bridge.
 874             Defaults to on.</para>
 875           </listitem>
 876         </varlistentry>
 877         <varlistentry>
 878           <term><varname>Cost=</varname></term>
 879           <listitem>
 880             <para>Sets the "cost" of sending packets of this interface.
 881             Each port in a bridge may have a different speed and the cost
 882             is used to decide which link to use. Faster interfaces
 883             should have lower costs.</para>
 884           </listitem>
 885         </varlistentry>
 886       </variablelist>
 887   </refsect1>
 888   <refsect1>
 889     <title>[BridgeFDB] Section Options</title>
 890       <para>The <literal>[BridgeFDB]</literal> section manages the
 891       forwarding database table of a port and accepts the following
 892       keys. Specify several <literal>[BridgeFDB]</literal> sections to
 893       configure several static MAC table entries.</para>
 894
 895       <variablelist class='network-directives'>
 896         <varlistentry>
 897           <term><varname>MACAddress=</varname></term>
 898           <listitem>
 899             <para>As in the <literal>[Network]</literal> section. This
 900             key is mandatory.</para>
 901           </listitem>
 902         </varlistentry>
 903         <varlistentry>
 904           <term><varname>VLANId=</varname></term>
 905           <listitem>
 906             <para>The VLAN ID for the new static MAC table entry. If
 907             omitted, no VLAN ID info is appended to the new static MAC
 908             table entry.</para>
 909           </listitem>
 910         </varlistentry>
 911       </variablelist>
 912   </refsect1>
 913
 914   <refsect1>
 915     <title>Example</title>
 916     <example>
 917       <title>/etc/systemd/network/50-static.network</title>
 918
 919       <programlisting>[Match]
 920 Name=enp2s0
 921
 922 [Network]
 923 Address=192.168.0.15/24
 924 Gateway=192.168.0.1</programlisting>
 925     </example>
 926
 927     <example>
 928       <title>/etc/systemd/network/80-dhcp.network</title>
 929
 930       <programlisting>[Match]
 931 Name=en*
 932
 933 [Network]
 934 DHCP=yes</programlisting>
 935     </example>
 936
 937     <example>
 938       <title>/etc/systemd/network/25-bridge-static.network</title>
 939
 940       <programlisting>[Match]
 941 Name=bridge0
 942
 943 [Network]
 944 Address=192.168.0.15/24
 945 Gateway=192.168.0.1
 946 DNS=192.168.0.1</programlisting>
 947     </example>
 948
 949     <example>
 950       <title>/etc/systemd/network/25-bridge-slave-interface.network</title>
 951
 952       <programlisting>[Match]
 953 Name=enp2s0
 954
 955 [Network]
 956 Bridge=bridge0</programlisting>
 957     </example>
 958     <example>
 959       <title>/etc/systemd/network/25-ipip.network</title>
 960
 961       <programlisting>[Match]
 962 Name=em1
 963
 964 [Network]
 965 Tunnel=ipip-tun</programlisting>
 966     </example>
 967
 968     <example>
 969       <title>/etc/systemd/network/25-sit.network</title>
 970
 971       <programlisting>[Match]
 972 Name=em1
 973
 974 [Network]
 975 Tunnel=sit-tun</programlisting>
 976     </example>
 977
 978     <example>
 979       <title>/etc/systemd/network/25-gre.network</title>
 980
 981       <programlisting>[Match]
 982 Name=em1
 983
 984 [Network]
 985 Tunnel=gre-tun</programlisting>
 986     </example>
 987
 988     <example>
 989       <title>/etc/systemd/network/25-vti.network</title>
 990
 991       <programlisting>[Match]
 992 Name=em1
 993
 994 [Network]
 995 Tunnel=vti-tun</programlisting>
 996     </example>
 997
 998     <example>
 999       <title>/etc/systemd/network/25-bond.network</title>
1000
1001       <programlisting>[Match]
1002 Name=bond1
1003
1004 [Network]
1005 DHCP=yes
1006 </programlisting>
1007     </example>
1008
1009   </refsect1>
1010
1011   <refsect1>
1012     <title>See Also</title>
1013     <para>
1014       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1015       <citerefentry><refentrytitle>systemd-networkd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1016       <citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1017       <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1018     </para>
1019   </refsect1>
1020
1021 </refentry>