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>Note that DHCPv6 will by default be triggered by Router
 231             Advertisement, 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,
 281             enables <ulink
 282             url="https://tools.ietf.org/html/rfc4795">Link-Local
 283             Multicast Name Resolution</ulink> on the link. When set to
 284             <literal>resolve</literal>, only resolution is enabled,
 285             but not host registration and announcement. Defaults to
 286             true. This setting is read by
 287             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 288           </listitem>
 289         </varlistentry>
 290         <varlistentry>
 291           <term><varname>MulticastDNS=</varname></term>
 292           <listitem>
 293             <para>A boolean or <literal>resolve</literal>. When true,
 294             enables <ulink
 295             url="https://tools.ietf.org/html/rfc6762">Multicast
 296             DNS</ulink> support on the link. When set to
 297             <literal>resolve</literal>, only resolution is enabled,
 298             but not host or service registration and
 299             announcement. Defaults to false. This setting is read by
 300             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 301           </listitem>
 302         </varlistentry>
 303         <varlistentry>
 304           <term><varname>DNSSEC=</varname></term>
 305           <listitem>
 306             <para>A boolean or
 307             <literal>allow-downgrade</literal>. When true, enables
 308             <ulink
 309             url="https://tools.ietf.org/html/rfc4033">DNSSEC</ulink>
 310             DNS validation support on the link. When set to
 311             <literal>allow-downgrade</literal>, compatibility with
 312             non-DNSSEC capable networks is increased, by automatically
 313             turning off DNSEC in this case. This option defines a
 314             per-interface setting for
 315             <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>'s
 316             global <varname>DNSSEC=</varname> option. Defaults to
 317             false. This setting is read by
 318             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 319           </listitem>
 320         </varlistentry>
 321         <varlistentry>
 322           <term><varname>DNSSECNegativeTrustAnchors=</varname></term>
 323           <listitem><para>A space-separated list of DNSSEC negative
 324           trust anchor domains. If specified and DNSSEC is enabled,
 325           look-ups done via the interface's DNS server will be subject
 326           to the list of negative trust anchors, and not require
 327           authentication for the specified domains, or anything below
 328           it. Use this to disable DNSSEC authentication for specific
 329           private domains, that cannot be proven valid using the
 330           Internet DNS hierarchy. Defaults to the empty list. This
 331           setting is read by
 332           <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 333           </listitem>
 334         </varlistentry>
 335         <varlistentry>
 336           <term><varname>LLDP=</varname></term>
 337           <listitem>
 338             <para>A boolean. When true, enables LLDP link receive support.
 339             </para>
 340           </listitem>
 341         </varlistentry>
 342         <varlistentry>
 343           <term><varname>BindCarrier=</varname></term>
 344           <listitem>
 345             <para>A port or a list of ports. When set, controls the
 346             behavior of the current interface. When all ports in the list
 347             are in an operational down state, the current interface is brought
 348             down. When at least one port has carrier, the current interface
 349             is brought up.
 350             </para>
 351           </listitem>
 352         </varlistentry>
 353         <varlistentry>
 354           <term><varname>Address=</varname></term>
 355           <listitem>
 356             <para>A static IPv4 or IPv6 address and its prefix length,
 357             separated by a <literal>/</literal> character. Specify
 358             this key more than once to configure several addresses.
 359             The format of the address must be as described in
 360             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 361             This is a short-hand for an [Address] section only
 362             containing an Address key (see below). This option may be
 363             specified more than once.
 364             </para>
 365
 366             <para>If the specified address is 0.0.0.0 (for IPv4) or
 367             [::] (for IPv6), a new address range of the requested size
 368             is automatically allocated from a system-wide pool of
 369             unused ranges. The allocated range is checked against all
 370             current network interfaces and all known network
 371             configuration files to avoid address range conflicts. The
 372             default system-wide pool consists of 192.168.0.0/16,
 373             172.16.0.0/12 and 10.0.0.0/8 for IPv4, and fc00::/7 for
 374             IPv6. This functionality is useful to manage a large
 375             number of dynamically created network interfaces with the
 376             same network configuration and automatic address range
 377             assignment.</para>
 378
 379           </listitem>
 380         </varlistentry>
 381         <varlistentry>
 382           <term><varname>Gateway=</varname></term>
 383           <listitem>
 384             <para>The gateway address, which must be in the format
 385             described in
 386             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 387             This is a short-hand for a [Route] section only containing
 388             a Gateway key. This option may be specified more than
 389             once.</para>
 390           </listitem>
 391         </varlistentry>
 392         <varlistentry>
 393           <term><varname>DNS=</varname></term>
 394           <listitem>
 395             <para>A DNS server address, which must be in the format
 396             described in
 397             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 398             This option may be specified more than once. This setting is read by
 399             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 400           </listitem>
 401         </varlistentry>
 402         <varlistentry>
 403           <term><varname>Domains=</varname></term>
 404           <listitem>
 405             <para>The domains used for DNS host name resolution on this link. Takes a list of DNS domain names which
 406             are used as search suffixes for extending single-label host names (host names containing no dots) to become
 407             fully qualified domain names (FQDNs). If a single-label host name is resolved on this interface, each of
 408             the specified search domains are appended to it in turn, converting it into a fully qualified domain name,
 409             until one of them may be successfully resolved.</para>
 410
 411             <para>The specified domains are also used for routing of DNS queries: look-ups for host names ending in the
 412             domains specified here are preferably routed to the DNS servers configured for this interface. If a domain
 413             name is prefixed with <literal>~</literal>, the domain name becomes a pure "routing" domain, is used for
 414             DNS query routing purposes only and is not used in the described domain search logic. By specifying a
 415             routing domain of <literal>~.</literal> (the tilda indicating definition of a routing domain, the dot
 416             referring to the DNS root domain which is the implied suffix of all valid DNS names) it is possible to
 417             route all DNS traffic preferably to the DNS server specified for this interface. The route domain logic is
 418             particularly useful on multi-homed hosts with DNS servers serving particular private DNS zones on each
 419             interface.</para>
 420
 421             <para>This setting is read by
 422             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 423           </listitem>
 424         </varlistentry>
 425         <varlistentry>
 426           <term><varname>NTP=</varname></term>
 427           <listitem>
 428             <para>An NTP server address. This option may be specified more than once. This setting is read by
 429             <citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 430           </listitem>
 431         </varlistentry>
 432         <varlistentry>
 433           <term><varname>IPForward=</varname></term>
 434           <listitem><para>Configures IP packet forwarding for the
 435           system. If enabled, incoming packets on any network
 436           interface will be forwarded to any other interfaces
 437           according to the routing table. Takes either a boolean
 438           argument, or the values <literal>ipv4</literal> or
 439           <literal>ipv6</literal>, which only enable IP packet
 440           forwarding for the specified address family.  This controls
 441           the <filename>net.ipv4.ip_forward</filename> and
 442           <filename>net.ipv6.conf.all.forwarding</filename> sysctl
 443           options of the network interface (see <ulink
 444           url="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">ip-sysctl.txt</ulink>
 445           for details about sysctl options). Defaults to
 446           <literal>no</literal>.</para>
 447
 448           <para>Note: this setting controls a global kernel option,
 449           and does so one way only: if a network that has this setting
 450           enabled is set up the global setting is turned on.  However,
 451           it is never turned off again, even after all networks with
 452           this setting enabled are shut down again.</para>
 453
 454           <para>To allow IP packet forwarding only between specific
 455           network interfaces use a firewall.</para>
 456           </listitem>
 457         </varlistentry>
 458         <varlistentry>
 459           <term><varname>IPMasquerade=</varname></term>
 460           <listitem><para>Configures IP masquerading for the network
 461           interface. If enabled, packets forwarded from the network
 462           interface will be appear as coming from the local host.
 463           Takes a boolean argument. Implies
 464           <varname>IPForward=ipv4</varname>. Defaults to
 465           <literal>no</literal>.</para></listitem>
 466         </varlistentry>
 467         <varlistentry>
 468           <term><varname>IPv6PrivacyExtensions=</varname></term>
 469           <listitem><para>Configures use of stateless temporary
 470           addresses that change over time (see <ulink
 471           url="https://tools.ietf.org/html/rfc4941">RFC 4941</ulink>,
 472           Privacy Extensions for Stateless Address Autoconfiguration
 473           in IPv6). Takes a boolean or the special values
 474           <literal>prefer-public</literal> and
 475           <literal>kernel</literal>. When true, enables the privacy
 476           extensions and prefers temporary addresses over public
 477           addresses. When <literal>prefer-public</literal>, enables the
 478           privacy extensions, but prefers public addresses over
 479           temporary addresses. When false, the privacy extensions
 480           remain disabled. When <literal>kernel</literal>, the kernel's
 481           default setting will be left in place.  Defaults to
 482           <literal>no</literal>.</para></listitem>
 483         </varlistentry>
 484         <varlistentry>
 485           <term><varname>IPv6AcceptRouterAdvertisements=</varname></term>
 486           <listitem><para>Force the setting of the <filename>accept_ra</filename>
 487           (router advertisements) setting for the interface.
 488           When unset, the kernel default is used, and router
 489           advertisements are accepted only when local forwarding
 490           is disabled for that interface.
 491           When router advertisements are accepted, they will
 492           trigger the start of the DHCPv6 client if the relevant
 493           flags are passed, or if no routers are found on the link.
 494           Takes a boolean. If true, router advertisements are
 495           accepted, when false, router advertisements are ignored,
 496           independently of the local forwarding state.</para>
 497
 498           <para>See
 499           <ulink url="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">ip-sysctl.txt</ulink>
 500           in the kernel documentation, but note that systemd's
 501           setting of <constant>1</constant> corresponds to
 502           kernel's setting of <constant>2</constant>.</para>
 503         </listitem>
 504         </varlistentry>
 505         <varlistentry>
 506           <term><varname>IPv6DuplicateAddressDetection=</varname></term>
 507           <listitem><para>Configures the amount of IPv6 Duplicate
 508           Address Detection (DAD) probes to send. Defaults to unset.
 509         </para></listitem>
 510         </varlistentry>
 511         <varlistentry>
 512           <term><varname>IPv6HopLimit=</varname></term>
 513           <listitem><para>Configures IPv6 Hop Limit. For each router that
 514           forwards the packet, the hop limit is decremented by 1. When the
 515           hop limit field reaches zero, the packet is discarded.
 516           Defaults to unset.
 517         </para></listitem>
 518         </varlistentry>
 519         <varlistentry>
 520           <term><varname>Bridge=</varname></term>
 521           <listitem>
 522             <para>The name of the bridge to add the link to.</para>
 523           </listitem>
 524         </varlistentry>
 525         <varlistentry>
 526           <term><varname>Bond=</varname></term>
 527           <listitem>
 528             <para>The name of the bond to add the link to.</para>
 529           </listitem>
 530         </varlistentry>
 531         <varlistentry>
 532           <term><varname>VLAN=</varname></term>
 533           <listitem>
 534             <para>The name of a VLAN to create on the link. This
 535             option may be specified more than once.</para>
 536           </listitem>
 537         </varlistentry>
 538         <varlistentry>
 539           <term><varname>MACVLAN=</varname></term>
 540           <listitem>
 541             <para>The name of a MACVLAN to create on the link. This
 542             option may be specified more than once.</para>
 543           </listitem>
 544         </varlistentry>
 545         <varlistentry>
 546           <term><varname>VXLAN=</varname></term>
 547           <listitem>
 548             <para>The name of a VXLAN to create on the link. This
 549             option may be specified more than once.</para>
 550           </listitem>
 551         </varlistentry>
 552         <varlistentry>
 553           <term><varname>Tunnel=</varname></term>
 554           <listitem>
 555             <para>The name of a Tunnel to create on the link. This
 556             option may be specified more than once.</para>
 557           </listitem>
 558         </varlistentry>
 559       </variablelist>
 560
 561   </refsect1>
 562
 563   <refsect1>
 564     <title>[Address] Section Options</title>
 565
 566       <para>An <literal>[Address]</literal> section accepts the
 567       following keys. Specify several <literal>[Address]</literal>
 568       sections to configure several addresses.</para>
 569
 570       <variablelist class='network-directives'>
 571         <varlistentry>
 572           <term><varname>Address=</varname></term>
 573           <listitem>
 574             <para>As in the <literal>[Network]</literal> section. This
 575             key is mandatory.</para>
 576           </listitem>
 577         </varlistentry>
 578         <varlistentry>
 579           <term><varname>Peer=</varname></term>
 580           <listitem>
 581             <para>The peer address in a point-to-point connection.
 582             Accepts the same format as the <literal>Address</literal>
 583             key.</para>
 584           </listitem>
 585         </varlistentry>
 586         <varlistentry>
 587           <term><varname>Broadcast=</varname></term>
 588           <listitem>
 589             <para>The broadcast address, which must be in the format
 590             described in
 591             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 592             This key only applies to IPv4 addresses. If it is not
 593             given, it is derived from the <literal>Address</literal>
 594             key.</para>
 595           </listitem>
 596         </varlistentry>
 597         <varlistentry>
 598           <term><varname>Label=</varname></term>
 599           <listitem>
 600             <para>An address label.</para>
 601           </listitem>
 602         </varlistentry>
 603       </variablelist>
 604   </refsect1>
 605
 606   <refsect1>
 607     <title>[Route] Section Options</title>
 608       <para>The <literal>[Route]</literal> section accepts the
 609       following keys. Specify several <literal>[Route]</literal>
 610       sections to configure several routes.</para>
 611
 612       <variablelist class='network-directives'>
 613         <varlistentry>
 614           <term><varname>Gateway=</varname></term>
 615           <listitem>
 616             <para>As in the <literal>[Network]</literal> section.</para>
 617           </listitem>
 618         </varlistentry>
 619         <varlistentry>
 620           <term><varname>Destination=</varname></term>
 621           <listitem>
 622             <para>The destination prefix of the route. Possibly
 623             followed by a slash and the prefix length. If omitted, a
 624             full-length host route is assumed.</para>
 625           </listitem>
 626         </varlistentry>
 627         <varlistentry>
 628           <term><varname>Source=</varname></term>
 629           <listitem>
 630             <para>The source prefix of the route. Possibly followed by
 631             a slash and the prefix length. If omitted, a full-length
 632             host route is assumed.</para>
 633           </listitem>
 634         </varlistentry>
 635         <varlistentry>
 636           <term><varname>Metric=</varname></term>
 637           <listitem>
 638             <para>The metric of the route (an unsigned integer).</para>
 639           </listitem>
 640         </varlistentry>
 641         <varlistentry>
 642           <term><varname>Scope=</varname></term>
 643           <listitem>
 644             <para>The scope of the route, which can be <literal>global</literal>,
 645             <literal>link</literal> or <literal>host</literal>. Defaults to
 646             <literal>global</literal>.</para>
 647           </listitem>
 648         </varlistentry>
 649         <varlistentry>
 650           <term><varname>PreferredSource=</varname></term>
 651           <listitem>
 652             <para>The preferred source address of the route. The address
 653             must be in the format described in
 654             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
 655           </listitem>
 656         </varlistentry>
 657       </variablelist>
 658   </refsect1>
 659
 660   <refsect1>
 661     <title>[DHCP] Section Options</title>
 662       <para>The <literal>[DHCP]</literal> section configures the
 663       DHCPv4 and DHCP6 client, if it is enabled with the
 664       <varname>DHCP=</varname> setting described above:</para>
 665
 666       <variablelist class='network-directives'>
 667         <varlistentry>
 668           <term><varname>UseDNS=</varname></term>
 669           <listitem>
 670             <para>When true (the default), the DNS servers received
 671             from the DHCP server will be used and take precedence over
 672             any statically configured ones.</para>
 673
 674             <para>This corresponds to the <option>nameserver</option>
 675             option in <citerefentry
 676             project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 677           </listitem>
 678         </varlistentry>
 679         <varlistentry>
 680           <term><varname>UseNTP=</varname></term>
 681           <listitem>
 682             <para>When true (the default), the NTP servers received
 683             from the DHCP server will be used by systemd-timesyncd
 684             and take precedence over any statically configured ones.</para>
 685           </listitem>
 686         </varlistentry>
 687         <varlistentry>
 688           <term><varname>UseMTU=</varname></term>
 689           <listitem>
 690             <para>When true, the interface maximum transmission unit
 691             from the DHCP server will be used on the current link.
 692             Defaults to false.</para>
 693           </listitem>
 694         </varlistentry>
 695         <varlistentry>
 696           <term><varname>SendHostname=</varname></term>
 697           <listitem>
 698             <para>When true (the default), the machine's hostname will
 699             be sent to the DHCP server.</para>
 700           </listitem>
 701         </varlistentry>
 702         <varlistentry>
 703           <term><varname>UseHostname=</varname></term>
 704           <listitem>
 705             <para>When true (the default), the hostname received from
 706             the DHCP server will be set as the transient hostname of the system
 707             </para>
 708           </listitem>
 709         </varlistentry>
 710         <varlistentry>
 711         <term><varname>Hostname=</varname></term>
 712         <listitem>
 713           <para>Use this value for the hostname which is sent to the
 714           DHCP server, instead of machine's hostname.</para>
 715         </listitem>
 716       </varlistentry>
 717         <varlistentry>
 718           <term><varname>UseDomains=</varname></term>
 719           <listitem>
 720             <para>When true (not the default), the domain name
 721             received from the DHCP server will be used for DNS
 722             resolution over this link. When a name cannot be resolved
 723             as specified, the domain name will be used a suffix and
 724             name resolution of that will be attempted.</para>
 725
 726             <para>This corresponds to the <option>domain</option>
 727             option in <citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 728             and should not be enabled on untrusted networks.</para>
 729           </listitem>
 730         </varlistentry>
 731         <varlistentry>
 732           <term><varname>UseRoutes=</varname></term>
 733           <listitem>
 734             <para>When true (the default), the static routes will be
 735             requested from the DHCP server and added to the routing
 736             table with a metric of 1024.</para>
 737           </listitem>
 738         </varlistentry>
 739
 740         <varlistentry>
 741           <term><varname>UseTimezone=</varname></term>
 742
 743           <listitem><para>When true, the timezone received from the
 744           DHCP server will be set as timezone of the local
 745           system. Defaults to <literal>no</literal>.</para></listitem>
 746         </varlistentry>
 747
 748         <varlistentry>
 749           <term><varname>CriticalConnection=</varname></term>
 750           <listitem>
 751             <para>When true, the connection will never be torn down
 752             even if the DHCP lease expires. This is contrary to the
 753             DHCP specification, but may be the best choice if, say,
 754             the root filesystem relies on this connection. Defaults to
 755             false.</para>
 756           </listitem>
 757         </varlistentry>
 758         <varlistentry>
 759           <term><varname>ClientIdentifier=</varname></term>
 760           <listitem>
 761             <para>DHCP client identifier to use. Either <literal>mac</literal>
 762             to use the MAC address of the link or <literal>duid</literal>
 763             (the default) to use a RFC4361-compliant Client ID.</para>
 764           </listitem>
 765         </varlistentry>
 766         <varlistentry>
 767           <term><varname>VendorClassIdentifier=</varname></term>
 768           <listitem>
 769             <para>The vendor class identifier used to identify vendor
 770             type and configuration.</para>
 771           </listitem>
 772         </varlistentry>
 773         <varlistentry>
 774           <term><varname>RequestBroadcast=</varname></term>
 775           <listitem>
 776             <para>Request the server to use broadcast messages before
 777             the IP address has been configured. This is necessary for
 778             devices that cannot receive RAW packets, or that cannot
 779             receive packets at all before an IP address has been
 780             configured. On the other hand, this must not be enabled on
 781             networks where broadcasts are filtered out.</para>
 782           </listitem>
 783         </varlistentry>
 784         <varlistentry>
 785           <term><varname>RouteMetric=</varname></term>
 786           <listitem>
 787             <para>Set the routing metric for routes specified by the
 788             DHCP server.</para>
 789           </listitem>
 790         </varlistentry>
 791       </variablelist>
 792
 793   </refsect1>
 794
 795   <refsect1>
 796     <title>[DHCPServer] Section Options</title>
 797     <para>The <literal>[DHCPServer]</literal> section contains
 798     settings for the DHCP server, if enabled via the
 799     <varname>DHCPServer=</varname> option described above:</para>
 800
 801     <variablelist class='network-directives'>
 802
 803       <varlistentry>
 804         <term><varname>PoolOffset=</varname></term>
 805         <term><varname>PoolSize=</varname></term>
 806
 807         <listitem><para>Configures the pool of addresses to hand out. The pool
 808         is a contiguous sequence of IP addresses in the subnet configured for
 809         the server address, which does not include the subnet nor the broadcast
 810         address. <varname>PoolOffset=</varname> takes the offset of the pool
 811         from the start of subnet, or zero to use the default value.
 812         <varname>PoolSize=</varname> takes the number of IP addresses in the
 813         pool or zero to use the default value. By default, the pool starts at
 814         the first address after the subnet address and takes up the rest of
 815         the subnet, excluding the broadcast address. If the pool includes
 816         the server address (the default), this is reserved and not handed
 817         out to clients.</para></listitem>
 818       </varlistentry>
 819
 820       <varlistentry>
 821         <term><varname>DefaultLeaseTimeSec=</varname></term>
 822         <term><varname>MaxLeaseTimeSec=</varname></term>
 823
 824         <listitem><para>Control the default and maximum DHCP lease
 825         time to pass to clients. These settings take time values in seconds or
 826         another common time unit, depending on the suffix. The default
 827         lease time is used for clients that did not ask for a specific
 828         lease time. If a client asks for a lease time longer than the
 829         maximum lease time, it is automatically shortened to the
 830         specified time. The default lease time defaults to 1h, the
 831         maximum lease time to 12h. Shorter lease times are beneficial
 832         if the configuration data in DHCP leases changes frequently
 833         and clients shall learn the new settings with shorter
 834         latencies. Longer lease times reduce the generated DHCP
 835         network traffic.</para></listitem>
 836       </varlistentry>
 837
 838       <varlistentry>
 839         <term><varname>EmitDNS=</varname></term>
 840         <term><varname>DNS=</varname></term>
 841
 842         <listitem><para>Configures whether the DHCP leases handed out
 843         to clients shall contain DNS server information. The
 844         <varname>EmitDNS=</varname> setting takes a boolean argument
 845         and defaults to <literal>yes</literal>. The DNS servers to
 846         pass to clients may be configured with the
 847         <varname>DNS=</varname> option, which takes a list of IPv4
 848         addresses. If the <varname>EmitDNS=</varname> option is
 849         enabled but no servers configured, the servers are
 850         automatically propagated from an "uplink" interface that has
 851         appropriate servers set. The "uplink" interface is determined
 852         by the default route of the system with the highest
 853         priority. Note that this information is acquired at the time
 854         the lease is handed out, and does not take uplink interfaces
 855         into account that acquire DNS or NTP server information at a
 856         later point. DNS server propagation does not take
 857         <filename>/etc/resolv.conf</filename> into account. Also, note
 858         that the leases are not refreshed if the uplink network
 859         configuration changes. To ensure clients regularly acquire the
 860         most current uplink DNS server information, it is thus
 861         advisable to shorten the DHCP lease time via
 862         <varname>MaxLeaseTimeSec=</varname> described
 863         above.</para></listitem>
 864       </varlistentry>
 865
 866       <varlistentry>
 867         <term><varname>EmitNTP=</varname></term>
 868         <term><varname>NTP=</varname></term>
 869
 870         <listitem><para>Similar to the <varname>EmitDNS=</varname> and
 871         <varname>DNS=</varname> settings described above, these
 872         settings configure whether and what NTP server information
 873         shall be emitted as part of the DHCP lease. The same syntax,
 874         propagation semantics and defaults apply as for
 875         <varname>EmitDNS=</varname> and
 876         <varname>DNS=</varname>.</para></listitem>
 877       </varlistentry>
 878
 879       <varlistentry>
 880         <term><varname>EmitTimezone=</varname></term>
 881         <term><varname>Timezone=</varname></term>
 882
 883         <listitem><para>Configures whether the DHCP leases handed out
 884         to clients shall contain timezone information. The
 885         <varname>EmitTimezone=</varname> setting takes a boolean
 886         argument and defaults to <literal>yes</literal>. The
 887         <varname>Timezone=</varname> setting takes a timezone string
 888         (such as <literal>Europe/Berlin</literal> or
 889         <literal>UTC</literal>) to pass to clients. If no explicit
 890         timezone is set, the system timezone of the local host is
 891         propagated, as determined by the
 892         <filename>/etc/localtime</filename> symlink.</para></listitem>
 893       </varlistentry>
 894
 895     </variablelist>
 896   </refsect1>
 897
 898   <refsect1>
 899     <title>[Bridge] Section Options</title>
 900       <para>The <literal>[Bridge]</literal> section accepts the
 901       following keys.</para>
 902       <variablelist class='network-directives'>
 903         <varlistentry>
 904           <term><varname>UnicastFlood=</varname></term>
 905           <listitem>
 906             <para>A boolean. Controls whether the bridge should flood
 907             traffic for which an FDB entry is missing and the destination
 908             is unknown through this port. Defaults to on.
 909             </para>
 910           </listitem>
 911         </varlistentry>
 912         <varlistentry>
 913           <term><varname>HairPin=</varname></term>
 914           <listitem>
 915             <para>A boolean. Configures whether traffic may be sent back
 916             out of the port on which it was received. By default, this
 917             flag is false, and the bridge will not forward traffic back
 918             out of the receiving port.</para>
 919           </listitem>
 920         </varlistentry>
 921         <varlistentry>
 922           <term><varname>UseBPDU=</varname></term>
 923           <listitem>
 924             <para>A boolean. Configures whether STP Bridge Protocol Data Units will be
 925             processed by the bridge port. Defaults to yes.</para>
 926           </listitem>
 927         </varlistentry>
 928         <varlistentry>
 929           <term><varname>FastLeave=</varname></term>
 930           <listitem>
 931             <para>A boolean. This flag allows the bridge to immediately stop multicast
 932             traffic on a port that receives an IGMP Leave message. It is only used with
 933             IGMP snooping if enabled on the bridge. Defaults to off.</para>
 934           </listitem>
 935         </varlistentry>
 936         <varlistentry>
 937           <term><varname>AllowPortToBeRoot=</varname></term>
 938           <listitem>
 939             <para>A boolean. Configures whether a given port is allowed to
 940             become a root port. Only used when STP is enabled on the bridge.
 941             Defaults to on.</para>
 942           </listitem>
 943         </varlistentry>
 944         <varlistentry>
 945           <term><varname>Cost=</varname></term>
 946           <listitem>
 947             <para>Sets the "cost" of sending packets of this interface.
 948             Each port in a bridge may have a different speed and the cost
 949             is used to decide which link to use. Faster interfaces
 950             should have lower costs.</para>
 951           </listitem>
 952         </varlistentry>
 953       </variablelist>
 954   </refsect1>
 955   <refsect1>
 956     <title>[BridgeFDB] Section Options</title>
 957       <para>The <literal>[BridgeFDB]</literal> section manages the
 958       forwarding database table of a port and accepts the following
 959       keys. Specify several <literal>[BridgeFDB]</literal> sections to
 960       configure several static MAC table entries.</para>
 961
 962       <variablelist class='network-directives'>
 963         <varlistentry>
 964           <term><varname>MACAddress=</varname></term>
 965           <listitem>
 966             <para>As in the <literal>[Network]</literal> section. This
 967             key is mandatory.</para>
 968           </listitem>
 969         </varlistentry>
 970         <varlistentry>
 971           <term><varname>VLANId=</varname></term>
 972           <listitem>
 973             <para>The VLAN ID for the new static MAC table entry. If
 974             omitted, no VLAN ID info is appended to the new static MAC
 975             table entry.</para>
 976           </listitem>
 977         </varlistentry>
 978       </variablelist>
 979   </refsect1>
 980
 981   <refsect1>
 982     <title>Example</title>
 983     <example>
 984       <title>/etc/systemd/network/50-static.network</title>
 985
 986       <programlisting>[Match]
 987 Name=enp2s0
 988
 989 [Network]
 990 Address=192.168.0.15/24
 991 Gateway=192.168.0.1</programlisting>
 992     </example>
 993
 994     <example>
 995       <title>/etc/systemd/network/80-dhcp.network</title>
 996
 997       <programlisting>[Match]
 998 Name=en*
 999
1000 [Network]
1001 DHCP=yes</programlisting>
1002     </example>
1003
1004     <example>
1005       <title>/etc/systemd/network/25-bridge-static.network</title>
1006
1007       <programlisting>[Match]
1008 Name=bridge0
1009
1010 [Network]
1011 Address=192.168.0.15/24
1012 Gateway=192.168.0.1
1013 DNS=192.168.0.1</programlisting>
1014     </example>
1015
1016     <example>
1017       <title>/etc/systemd/network/25-bridge-slave-interface.network</title>
1018
1019       <programlisting>[Match]
1020 Name=enp2s0
1021
1022 [Network]
1023 Bridge=bridge0</programlisting>
1024     </example>
1025     <example>
1026       <title>/etc/systemd/network/25-ipip.network</title>
1027
1028       <programlisting>[Match]
1029 Name=em1
1030
1031 [Network]
1032 Tunnel=ipip-tun</programlisting>
1033     </example>
1034
1035     <example>
1036       <title>/etc/systemd/network/25-sit.network</title>
1037
1038       <programlisting>[Match]
1039 Name=em1
1040
1041 [Network]
1042 Tunnel=sit-tun</programlisting>
1043     </example>
1044
1045     <example>
1046       <title>/etc/systemd/network/25-gre.network</title>
1047
1048       <programlisting>[Match]
1049 Name=em1
1050
1051 [Network]
1052 Tunnel=gre-tun</programlisting>
1053     </example>
1054
1055     <example>
1056       <title>/etc/systemd/network/25-vti.network</title>
1057
1058       <programlisting>[Match]
1059 Name=em1
1060
1061 [Network]
1062 Tunnel=vti-tun</programlisting>
1063     </example>
1064
1065     <example>
1066       <title>/etc/systemd/network/25-bond.network</title>
1067
1068       <programlisting>[Match]
1069 Name=bond1
1070
1071 [Network]
1072 DHCP=yes
1073 </programlisting>
1074     </example>
1075
1076   </refsect1>
1077
1078   <refsect1>
1079     <title>See Also</title>
1080     <para>
1081       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1082       <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1083       <citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1084       <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1085       <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
1086     </para>
1087   </refsect1>
1088
1089 </refentry>