1SYSTEMD.NETWORK(5)              systemd.network             SYSTEMD.NETWORK(5)
2
3
4

NAME

6       systemd.network - Network configuration
7

SYNOPSIS

9       network.network
10

DESCRIPTION

12       A plain ini-style text file that encodes network configuration for
13       matching network interfaces, used by systemd-networkd(8). See
14       systemd.syntax(7) for a general description of the syntax.
15
16       The main network file must have the extension .network; other
17       extensions are ignored. Networks are applied to links whenever the
18       links appear.
19
20       The .network files are read from the files located in the system
21       network directories /usr/lib/systemd/network and
22       /usr/local/lib/systemd/network, the volatile runtime network directory
23       /run/systemd/network and the local administration network directory
24       /etc/systemd/network. All configuration files are collectively sorted
25       and processed in lexical order, regardless of the directories in which
26       they live. However, files with identical filenames replace each other.
27       Files in /etc have the highest priority, files in /run take precedence
28       over files with the same name under /usr. This can be used to override
29       a system-supplied configuration file with a local file if needed. As a
30       special case, an empty file (file size 0) or symlink with the same name
31       pointing to /dev/null disables the configuration file entirely (it is
32       "masked").
33
34       Along with the network file foo.network, a "drop-in" directory
35       foo.network.d/ may exist. All files with the suffix ".conf" from this
36       directory will be parsed after the file itself is parsed. This is
37       useful to alter or add configuration settings, without having to modify
38       the main configuration file. Each drop-in file must have appropriate
39       section headers.
40
41       In addition to /etc/systemd/network, drop-in ".d" directories can be
42       placed in /usr/lib/systemd/network or /run/systemd/network directories.
43       Drop-in files in /etc take precedence over those in /run which in turn
44       take precedence over those in /usr/lib. Drop-in files under any of
45       these directories take precedence over the main network file wherever
46       located.
47

[MATCH] SECTION OPTIONS

49       The network file contains a [Match] section, which determines if a
50       given network file may be applied to a given device; and a [Network]
51       section specifying how the device should be configured. The first (in
52       lexical order) of the network files that matches a given device is
53       applied, all later files are ignored, even if they match as well.
54
55       A network file is said to match a network interface if all matches
56       specified by the [Match] section are satisfied. When a network file
57       does not contain valid settings in [Match] section, then the file will
58       match all interfaces and systemd-networkd warns about that. Hint: to
59       avoid the warning and to make it clear that all interfaces shall be
60       matched, add the following:
61
62           Name=*
63
64       The following keys are accepted:
65
66       MACAddress=
67           A whitespace-separated list of hardware addresses. Use full colon-,
68           hyphen- or dot-delimited hexadecimal. See the example below. This
69           option may appear more than once, in which case the lists are
70           merged. If the empty string is assigned to this option, the list of
71           hardware addresses defined prior to this is reset.
72
73           Example:
74
75               MACAddress=01:23:45:67:89:ab 00-11-22-33-44-55 AABB.CCDD.EEFF
76
77       PermanentMACAddress=
78           A whitespace-separated list of hardware's permanent addresses.
79           While MACAddress= matches the device's current MAC address, this
80           matches the device's permanent MAC address, which may be different
81           from the current one. Use full colon-, hyphen- or dot-delimited
82           hexadecimal. This option may appear more than once, in which case
83           the lists are merged. If the empty string is assigned to this
84           option, the list of hardware addresses defined prior to this is
85           reset.
86
87       Path=
88           A whitespace-separated list of shell-style globs matching the
89           persistent path, as exposed by the udev property ID_PATH.
90
91       Driver=
92           A whitespace-separated list of shell-style globs matching the
93           driver currently bound to the device, as exposed by the udev
94           property ID_NET_DRIVER of its parent device, or if that is not set,
95           the driver as exposed by ethtool -i of the device itself. If the
96           list is prefixed with a "!", the test is inverted.
97
98       Type=
99           A whitespace-separated list of shell-style globs matching the
100           device type, as exposed by networkctl status. If the list is
101           prefixed with a "!", the test is inverted.
102
103       Property=
104           A whitespace-separated list of udev property name with its value
105           after a equal ("="). If multiple properties are specified, the test
106           results are ANDed. If the list is prefixed with a "!", the test is
107           inverted. If a value contains white spaces, then please quote whole
108           key and value pair. If a value contains quotation, then please
109           escape the quotation with "\".
110
111           Example: if a .link file has the following:
112
113               Property=ID_MODEL_ID=9999 "ID_VENDOR_FROM_DATABASE=vendor name" "KEY=with \"quotation\""
114
115           then, the .link file matches only when an interface has all the
116           above three properties.
117
118       Name=
119           A whitespace-separated list of shell-style globs matching the
120           device name, as exposed by the udev property "INTERFACE", or
121           device's alternative names. If the list is prefixed with a "!", the
122           test is inverted.
123
124       WLANInterfaceType=
125           A whitespace-separated list of wireless network type. Supported
126           values are "ad-hoc", "station", "ap", "ap-vlan", "wds", "monitor",
127           "mesh-point", "p2p-client", "p2p-go", "p2p-device", "ocb", and
128           "nan". If the list is prefixed with a "!", the test is inverted.
129
130       SSID=
131           A whitespace-separated list of shell-style globs matching the SSID
132           of the currently connected wireless LAN. If the list is prefixed
133           with a "!", the test is inverted.
134
135       BSSID=
136           A whitespace-separated list of hardware address of the currently
137           connected wireless LAN. Use full colon-, hyphen- or dot-delimited
138           hexadecimal. See the example in MACAddress=. This option may appear
139           more than once, in which case the lists are merged. If the empty
140           string is assigned to this option, the list is reset.
141
142       Host=
143           Matches against the hostname or machine ID of the host. See
144           ConditionHost= in systemd.unit(5) for details. When prefixed with
145           an exclamation mark ("!"), the result is negated. If an empty
146           string is assigned, then previously assigned value is cleared.
147
148       Virtualization=
149           Checks whether the system is executed in a virtualized environment
150           and optionally test whether it is a specific implementation. See
151           ConditionVirtualization= in systemd.unit(5) for details. When
152           prefixed with an exclamation mark ("!"), the result is negated. If
153           an empty string is assigned, then previously assigned value is
154           cleared.
155
156       KernelCommandLine=
157           Checks whether a specific kernel command line option is set. See
158           ConditionKernelCommandLine= in systemd.unit(5) for details. When
159           prefixed with an exclamation mark ("!"), the result is negated. If
160           an empty string is assigned, then previously assigned value is
161           cleared.
162
163       KernelVersion=
164           Checks whether the kernel version (as reported by uname -r) matches
165           a certain expression. See ConditionKernelVersion= in
166           systemd.unit(5) for details. When prefixed with an exclamation mark
167           ("!"), the result is negated. If an empty string is assigned, then
168           previously assigned value is cleared.
169
170       Architecture=
171           Checks whether the system is running on a specific architecture.
172           See ConditionArchitecture= in systemd.unit(5) for details. When
173           prefixed with an exclamation mark ("!"), the result is negated. If
174           an empty string is assigned, then previously assigned value is
175           cleared.
176

[LINK] SECTION OPTIONS

178       The [Link] section accepts the following keys:
179
180       MACAddress=
181           The hardware address to set for the device.
182
183       MTUBytes=
184           The maximum transmission unit in bytes to set for the device. The
185           usual suffixes K, M, G, are supported and are understood to the
186           base of 1024.
187
188           Note that if IPv6 is enabled on the interface, and the MTU is
189           chosen below 1280 (the minimum MTU for IPv6) it will automatically
190           be increased to this value.
191
192       ARP=
193           Takes a boolean. If set to true, the ARP (low-level Address
194           Resolution Protocol) for this interface is enabled. When unset, the
195           kernel's default will be used.
196
197           For example, disabling ARP is useful when creating multiple MACVLAN
198           or VLAN virtual interfaces atop a single lower-level physical
199           interface, which will then only serve as a link/"bridge" device
200           aggregating traffic to the same physical link and not participate
201           in the network otherwise.
202
203       Multicast=
204           Takes a boolean. If set to true, the multicast flag on the device
205           is enabled.
206
207       AllMulticast=
208           Takes a boolean. If set to true, the driver retrieves all multicast
209           packets from the network. This happens when multicast routing is
210           enabled.
211
212       Unmanaged=
213           Takes a boolean. When "yes", no attempts are made to bring up or
214           configure matching links, equivalent to when there are no matching
215           network files. Defaults to "no".
216
217           This is useful for preventing later matching network files from
218           interfering with certain interfaces that are fully controlled by
219           other applications.
220
221       Group=
222           Link groups are similar to port ranges found in managed switches.
223           When network interfaces are added to a numbered group, operations
224           on all the interfaces from that group can be performed at once. An
225           unsigned integer in the range 0—4294967294. Defaults to unset.
226
227       RequiredForOnline=
228           Takes a boolean or a minimum operational state and an optional
229           maximum operational state. Please see networkctl(1) for possible
230           operational states. When "yes", the network is deemed required when
231           determining whether the system is online when running
232           systemd-networkd-wait-online. When "no", the network is ignored
233           when checking for online state. When a minimum operational state
234           and an optional maximum operational state are set, "yes" is
235           implied, and this controls the minimum and maximum operational
236           state required for the network interface to be considered online.
237           Defaults to "yes".
238
239           The network will be brought up normally in all cases, but in the
240           event that there is no address being assigned by DHCP or the cable
241           is not plugged in, the link will simply remain offline and be
242           skipped automatically by systemd-networkd-wait-online if
243           "RequiredForOnline=no".
244

[SR-IOV] SECTION OPTIONS

246       The [SR-IOV] section accepts the following keys. Specify several
247       [SR-IOV] sections to configure several SR-IOVs. SR-IOV provides the
248       ability to partition a single physical PCI resource into virtual PCI
249       functions which can then be injected into a VM. In the case of network
250       VFs, SR-IOV improves north-south network performance (that is, traffic
251       with endpoints outside the host machine) by allowing traffic to bypass
252       the host machine’s network stack.
253
254       VirtualFunction=
255           Specifies a Virtual Function (VF), lightweight PCIe function
256           designed solely to move data in and out. Takes an unsigned integer
257           in the range 0..2147483646. This option is compulsory.
258
259       VLANId=
260           Specifies VLAN ID of the virtual function. Takes an unsigned
261           integer in the range 1..4095.
262
263       QualityOfService=
264           Specifies quality of service of the virtual function. Takes an
265           unsigned integer in the range 1..4294967294.
266
267       VLANProtocol=
268           Specifies VLAN protocol of the virtual function. Takes "802.1Q" or
269           "802.1ad".
270
271       MACSpoofCheck=
272           Takes a boolean. Controls the MAC spoof checking. When unset, the
273           kernel's default will be used.
274
275       QueryReceiveSideScaling=
276           Takes a boolean. Toggle the ability of querying the receive side
277           scaling (RSS) configuration of the virtual function (VF). The VF
278           RSS information like RSS hash key may be considered sensitive on
279           some devices where this information is shared between VF and the
280           physical function (PF). When unset, the kernel's default will be
281           used.
282
283       Trust=
284           Takes a boolean. Allows to set trust mode of the virtual function
285           (VF). When set, VF users can set a specific feature which may
286           impact security and/or performance. When unset, the kernel's
287           default will be used.
288
289       LinkState=
290           Allows to set the link state of the virtual function (VF). Takes a
291           boolean or a special value "auto". Setting to "auto" means a
292           reflection of the physical function (PF) link state, "yes" lets the
293           VF to communicate with other VFs on this host even if the PF link
294           state is down, "no" causes the hardware to drop any packets sent by
295           the VF. When unset, the kernel's default will be used.
296
297       MACAddress=
298           Specifies the MAC address for the virtual function.
299

[NETWORK] SECTION OPTIONS

301       The [Network] section accepts the following keys:
302
303       Description=
304           A description of the device. This is only used for presentation
305           purposes.
306
307       DHCP=
308           Enables DHCPv4 and/or DHCPv6 client support. Accepts "yes", "no",
309           "ipv4", or "ipv6". Defaults to "no".
310
311           Note that DHCPv6 will by default be triggered by Router
312           Advertisement, if that is enabled, regardless of this parameter. By
313           enabling DHCPv6 support explicitly, the DHCPv6 client will be
314           started regardless of the presence of routers on the link, or what
315           flags the routers pass. See "IPv6AcceptRA=".
316
317           Furthermore, note that by default the domain name specified through
318           DHCP is not used for name resolution. See option UseDomains= below.
319
320           See the [DHCPv4] or [DHCPv6] sections below for further
321           configuration options for the DHCP client support.
322
323       DHCPServer=
324           Takes a boolean. If set to "yes", DHCPv4 server will be started.
325           Defaults to "no". Further settings for the DHCP server may be set
326           in the [DHCPServer] section described below.
327
328       LinkLocalAddressing=
329           Enables link-local address autoconfiguration. Accepts "yes", "no",
330           "ipv4", "ipv6", "fallback", or "ipv4-fallback". If "fallback" or
331           "ipv4-fallback" is specified, then an IPv4 link-local address is
332           configured only when DHCPv4 fails. If "fallback", an IPv6
333           link-local address is always configured, and if "ipv4-fallback",
334           the address is not configured. Note that, the fallback mechanism
335           works only when DHCPv4 client is enabled, that is, it requires
336           "DHCP=yes" or "DHCP=ipv4". If Bridge= is set, defaults to "no", and
337           if not, defaults to "ipv6".
338
339       IPv6LinkLocalAddressGenerationMode=
340           Specifies how IPv6 link local address is generated. Takes one of
341           "eui64", "none", "stable-privacy" and "random". When unset, the
342           kernel's default will be used. Note that if LinkLocalAdressing= not
343           configured as "ipv6" then IPv6LinkLocalAddressGenerationMode= is
344           ignored.
345
346       IPv4LLRoute=
347           Takes a boolean. If set to true, sets up the route needed for
348           non-IPv4LL hosts to communicate with IPv4LL-only hosts. Defaults to
349           false.
350
351       DefaultRouteOnDevice=
352           Takes a boolean. If set to true, sets up the default route bound to
353           the interface. Defaults to false. This is useful when creating
354           routes on point-to-point interfaces. This is equivalent to e.g. the
355           following.
356
357               ip route add default dev veth99
358
359       IPv6Token=
360           Specifies an optional address generation mode and a required IPv6
361           address. If the mode is present, the two parts must be separated
362           with a colon "mode:address". The address generation mode may be
363           either prefixstable or static. If not specified, static is assumed.
364
365           When the mode is set to static, or unspecified, the lower bits of
366           the supplied address are combined with the upper bits of a prefix
367           received in a Router Advertisement message to form a complete
368           address. Note that if multiple prefixes are received in an RA
369           message, or in multiple RA messages, addresses will be formed from
370           each of them using the supplied address. This mode implements SLAAC
371           but uses a static interface identifier instead of an identifier
372           generated using the EUI-64 algorithm. Because the interface
373           identifier is static, if Duplicate Address Detection detects that
374           the computed address is a duplicate (in use by another node on the
375           link), then this mode will fail to provide an address for that
376           prefix.
377
378           When the mode is set to "prefixstable" the RFC 7217 algorithm for
379           generating interface identifiers will be used, but only when a
380           prefix received in an RA message matches the supplied address. See
381           RFC 7217[1]. Prefix matching will be attempted against each
382           prefixstable IPv6Token variable provided in the configuration; if a
383           received prefix does not match any of the provided addresses, then
384           the EUI-64 algorithm will be used to form an interface identifier
385           for that prefix. This mode is also SLAAC, but with a potentially
386           stable interface identifier which does not directly map to the
387           interface's hardware address. Note that the prefixstable algorithm
388           includes both the interface's name and MAC address in the hash used
389           to compute the interface identifier, so if either of those are
390           changed the resulting interface identifier (and address) will
391           change, even if the prefix received in the RA message has not
392           changed. Note that if multiple prefixstable IPv6Token variables are
393           supplied with addresses that match a prefix received in an RA
394           message, only the first one will be used to generate addresses.
395
396       LLMNR=
397           Takes a boolean or "resolve". When true, enables Link-Local
398           Multicast Name Resolution[2] on the link. When set to "resolve",
399           only resolution is enabled, but not host registration and
400           announcement. Defaults to true. This setting is read by systemd-
401           resolved.service(8).
402
403       MulticastDNS=
404           Takes a boolean or "resolve". When true, enables Multicast DNS[3]
405           support on the link. When set to "resolve", only resolution is
406           enabled, but not host or service registration and announcement.
407           Defaults to false. This setting is read by systemd-
408           resolved.service(8).
409
410       DNSOverTLS=
411           Takes a boolean or "opportunistic". When true, enables
412           DNS-over-TLS[4] support on the link. When set to "opportunistic",
413           compatibility with non-DNS-over-TLS servers is increased, by
414           automatically turning off DNS-over-TLS servers in this case. This
415           option defines a per-interface setting for resolved.conf(5)'s
416           global DNSOverTLS= option. Defaults to false. This setting is read
417           by systemd-resolved.service(8).
418
419       DNSSEC=
420           Takes a boolean or "allow-downgrade". When true, enables DNSSEC[5]
421           DNS validation support on the link. When set to "allow-downgrade",
422           compatibility with non-DNSSEC capable networks is increased, by
423           automatically turning off DNSSEC in this case. This option defines
424           a per-interface setting for resolved.conf(5)'s global DNSSEC=
425           option. Defaults to false. This setting is read by systemd-
426           resolved.service(8).
427
428       DNSSECNegativeTrustAnchors=
429           A space-separated list of DNSSEC negative trust anchor domains. If
430           specified and DNSSEC is enabled, look-ups done via the interface's
431           DNS server will be subject to the list of negative trust anchors,
432           and not require authentication for the specified domains, or
433           anything below it. Use this to disable DNSSEC authentication for
434           specific private domains, that cannot be proven valid using the
435           Internet DNS hierarchy. Defaults to the empty list. This setting is
436           read by systemd-resolved.service(8).
437
438       LLDP=
439           Controls support for Ethernet LLDP packet reception. LLDP is a
440           link-layer protocol commonly implemented on professional routers
441           and bridges which announces which physical port a system is
442           connected to, as well as other related data. Accepts a boolean or
443           the special value "routers-only". When true, incoming LLDP packets
444           are accepted and a database of all LLDP neighbors maintained. If
445           "routers-only" is set only LLDP data of various types of routers is
446           collected and LLDP data about other types of devices ignored (such
447           as stations, telephones and others). If false, LLDP reception is
448           disabled. Defaults to "routers-only". Use networkctl(1) to query
449           the collected neighbor data. LLDP is only available on Ethernet
450           links. See EmitLLDP= below for enabling LLDP packet emission from
451           the local system.
452
453       EmitLLDP=
454           Controls support for Ethernet LLDP packet emission. Accepts a
455           boolean parameter or the special values "nearest-bridge",
456           "non-tpmr-bridge" and "customer-bridge". Defaults to false, which
457           turns off LLDP packet emission. If not false, a short LLDP packet
458           with information about the local system is sent out in regular
459           intervals on the link. The LLDP packet will contain information
460           about the local hostname, the local machine ID (as stored in
461           machine-id(5)) and the local interface name, as well as the pretty
462           hostname of the system (as set in machine-info(5)). LLDP emission
463           is only available on Ethernet links. Note that this setting passes
464           data suitable for identification of host to the network and should
465           thus not be enabled on untrusted networks, where such
466           identification data should not be made available. Use this option
467           to permit other systems to identify on which interfaces they are
468           connected to this system. The three special values control
469           propagation of the LLDP packets. The "nearest-bridge" setting
470           permits propagation only to the nearest connected bridge,
471           "non-tpmr-bridge" permits propagation across Two-Port MAC Relays,
472           but not any other bridges, and "customer-bridge" permits
473           propagation until a customer bridge is reached. For details about
474           these concepts, see IEEE 802.1AB-2016[6]. Note that configuring
475           this setting to true is equivalent to "nearest-bridge", the
476           recommended and most restricted level of propagation. See LLDP=
477           above for an option to enable LLDP reception.
478
479       BindCarrier=
480           A link name or a list of link names. When set, controls the
481           behavior of the current link. When all links in the list are in an
482           operational down state, the current link is brought down. When at
483           least one link has carrier, the current interface is brought up.
484
485       Address=
486           A static IPv4 or IPv6 address and its prefix length, separated by a
487           "/" character. Specify this key more than once to configure several
488           addresses. The format of the address must be as described in
489           inet_pton(3). This is a short-hand for an [Address] section only
490           containing an Address key (see below). This option may be specified
491           more than once.
492
493           If the specified address is "0.0.0.0" (for IPv4) or "::" (for
494           IPv6), a new address range of the requested size is automatically
495           allocated from a system-wide pool of unused ranges. Note that the
496           prefix length must be equal or larger than 8 for IPv4, and 64 for
497           IPv6. The allocated range is checked against all current network
498           interfaces and all known network configuration files to avoid
499           address range conflicts. The default system-wide pool consists of
500           192.168.0.0/16, 172.16.0.0/12 and 10.0.0.0/8 for IPv4, and fd00::/8
501           for IPv6. This functionality is useful to manage a large number of
502           dynamically created network interfaces with the same network
503           configuration and automatic address range assignment.
504
505       Gateway=
506           The gateway address, which must be in the format described in
507           inet_pton(3). This is a short-hand for a [Route] section only
508           containing a Gateway key. This option may be specified more than
509           once.
510
511       DNS=
512           A DNS server address, which must be in the format described in
513           inet_pton(3). This option may be specified more than once. Each
514           address can optionally take a port number separated with ":", a
515           network interface name or index separated with "%", and a Server
516           Name Indication (SNI) separated with "#". When IPv6 address is
517           specified with a port number, then the address must be in the
518           square brackets. That is, the acceptable full formats are
519           "111.222.333.444:9953%ifname#example.com" for IPv4 and
520           "[1111:2222::3333]:9953%ifname#example.com" for IPv6. This setting
521           can be specified multiple times. If an empty string is assigned,
522           then the all previous assignments are cleared. This setting is read
523           by systemd-resolved.service(8).
524
525       Domains=
526           A whitespace-separated list of domains which should be resolved
527           using the DNS servers on this link. Each item in the list should be
528           a domain name, optionally prefixed with a tilde ("~"). The domains
529           with the prefix are called "routing-only domains". The domains
530           without the prefix are called "search domains" and are first used
531           as search suffixes for extending single-label hostnames (hostnames
532           containing no dots) to become fully qualified domain names (FQDNs).
533           If a single-label hostname is resolved on this interface, each of
534           the specified search domains are appended to it in turn, converting
535           it into a fully qualified domain name, until one of them may be
536           successfully resolved.
537
538           Both "search" and "routing-only" domains are used for routing of
539           DNS queries: look-ups for hostnames ending in those domains (hence
540           also single label names, if any "search domains" are listed), are
541           routed to the DNS servers configured for this interface. The domain
542           routing logic is particularly useful on multi-homed hosts with DNS
543           servers serving particular private DNS zones on each interface.
544
545           The "routing-only" domain "~."  (the tilde indicating definition of
546           a routing domain, the dot referring to the DNS root domain which is
547           the implied suffix of all valid DNS names) has special effect. It
548           causes all DNS traffic which does not match another configured
549           domain routing entry to be routed to DNS servers specified for this
550           interface. This setting is useful to prefer a certain set of DNS
551           servers if a link on which they are connected is available.
552
553           This setting is read by systemd-resolved.service(8). "Search
554           domains" correspond to the domain and search entries in
555           resolv.conf(5). Domain name routing has no equivalent in the
556           traditional glibc API, which has no concept of domain name servers
557           limited to a specific link.
558
559       DNSDefaultRoute=
560           Takes a boolean argument. If true, this link's configured DNS
561           servers are used for resolving domain names that do not match any
562           link's configured Domains= setting. If false, this link's
563           configured DNS servers are never used for such domains, and are
564           exclusively used for resolving names that match at least one of the
565           domains configured on this link. If not specified defaults to an
566           automatic mode: queries not matching any link's configured domains
567           will be routed to this link if it has no routing-only domains
568           configured.
569
570       NTP=
571           An NTP server address (either an IP address, or a hostname). This
572           option may be specified more than once. This setting is read by
573           systemd-timesyncd.service(8).
574
575       IPForward=
576           Configures IP packet forwarding for the system. If enabled,
577           incoming packets on any network interface will be forwarded to any
578           other interfaces according to the routing table. Takes a boolean,
579           or the values "ipv4" or "ipv6", which only enable IP packet
580           forwarding for the specified address family. This controls the
581           net.ipv4.ip_forward and net.ipv6.conf.all.forwarding sysctl options
582           of the network interface (see ip-sysctl.txt[7] for details about
583           sysctl options). Defaults to "no".
584
585           Note: this setting controls a global kernel option, and does so one
586           way only: if a network that has this setting enabled is set up the
587           global setting is turned on. However, it is never turned off again,
588           even after all networks with this setting enabled are shut down
589           again.
590
591           To allow IP packet forwarding only between specific network
592           interfaces use a firewall.
593
594       IPMasquerade=
595           Configures IP masquerading for the network interface. If enabled,
596           packets forwarded from the network interface will be appear as
597           coming from the local host. Takes a boolean argument. Implies
598           IPForward=ipv4. Defaults to "no".
599
600       IPv6PrivacyExtensions=
601           Configures use of stateless temporary addresses that change over
602           time (see RFC 4941[8], Privacy Extensions for Stateless Address
603           Autoconfiguration in IPv6). Takes a boolean or the special values
604           "prefer-public" and "kernel". When true, enables the privacy
605           extensions and prefers temporary addresses over public addresses.
606           When "prefer-public", enables the privacy extensions, but prefers
607           public addresses over temporary addresses. When false, the privacy
608           extensions remain disabled. When "kernel", the kernel's default
609           setting will be left in place. Defaults to "no".
610
611       IPv6AcceptRA=
612           Takes a boolean. Controls IPv6 Router Advertisement (RA) reception
613           support for the interface. If true, RAs are accepted; if false, RAs
614           are ignored. When RAs are accepted, they may trigger the start of
615           the DHCPv6 client if the relevant flags are set in the RA data, or
616           if no routers are found on the link. The default is to disable RA
617           reception for bridge devices or when IP forwarding is enabled, and
618           to enable it otherwise. Cannot be enabled on bond devices and when
619           link local addressing is disabled.
620
621           Further settings for the IPv6 RA support may be configured in the
622           [IPv6AcceptRA] section, see below.
623
624           Also see ip-sysctl.txt[7] in the kernel documentation regarding
625           "accept_ra", but note that systemd's setting of 1 (i.e. true)
626           corresponds to kernel's setting of 2.
627
628           Note that kernel's implementation of the IPv6 RA protocol is always
629           disabled, regardless of this setting. If this option is enabled, a
630           userspace implementation of the IPv6 RA protocol is used, and the
631           kernel's own implementation remains disabled, since
632           systemd-networkd needs to know all details supplied in the
633           advertisements, and these are not available from the kernel if the
634           kernel's own implementation is used.
635
636       IPv6DuplicateAddressDetection=
637           Configures the amount of IPv6 Duplicate Address Detection (DAD)
638           probes to send. When unset, the kernel's default will be used.
639
640       IPv6HopLimit=
641           Configures IPv6 Hop Limit. For each router that forwards the
642           packet, the hop limit is decremented by 1. When the hop limit field
643           reaches zero, the packet is discarded. When unset, the kernel's
644           default will be used.
645
646       IPv4AcceptLocal=
647           Takes a boolean. Accept packets with local source addresses. In
648           combination with suitable routing, this can be used to direct
649           packets between two local interfaces over the wire and have them
650           accepted properly. When unset, the kernel's default will be used.
651
652       IPv4ProxyARP=
653           Takes a boolean. Configures proxy ARP for IPv4. Proxy ARP is the
654           technique in which one host, usually a router, answers ARP requests
655           intended for another machine. By "faking" its identity, the router
656           accepts responsibility for routing packets to the "real"
657           destination. See RFC 1027[9]. When unset, the kernel's default will
658           be used.
659
660       IPv6ProxyNDP=
661           Takes a boolean. Configures proxy NDP for IPv6. Proxy NDP (Neighbor
662           Discovery Protocol) is a technique for IPv6 to allow routing of
663           addresses to a different destination when peers expect them to be
664           present on a certain physical link. In this case a router answers
665           Neighbour Advertisement messages intended for another machine by
666           offering its own MAC address as destination. Unlike proxy ARP for
667           IPv4, it is not enabled globally, but will only send Neighbour
668           Advertisement messages for addresses in the IPv6 neighbor proxy
669           table, which can also be shown by ip -6 neighbour show proxy.
670           systemd-networkd will control the per-interface `proxy_ndp` switch
671           for each configured interface depending on this option. When unset,
672           the kernel's default will be used.
673
674       IPv6ProxyNDPAddress=
675           An IPv6 address, for which Neighbour Advertisement messages will be
676           proxied. This option may be specified more than once.
677           systemd-networkd will add the IPv6ProxyNDPAddress= entries to the
678           kernel's IPv6 neighbor proxy table. This option implies
679           IPv6ProxyNDP=yes but has no effect if IPv6ProxyNDP has been set to
680           false. When unset, the kernel's default will be used.
681
682       IPv6PrefixDelegation=
683           Whether to enable or disable Router Advertisement sending on a
684           link. Allowed values are "static" which distributes prefixes as
685           defined in the [IPv6PrefixDelegation] and any [IPv6Prefix]
686           sections, "dhcpv6" which requests prefixes using a DHCPv6 client
687           configured for another link and any values configured in the
688           [IPv6PrefixDelegation] section while ignoring all static prefix
689           configuration sections, "yes" which uses both static configuration
690           and DHCPv6, and "false" which turns off IPv6 prefix delegation
691           altogether. Defaults to "false". See the [IPv6PrefixDelegation] and
692           the [IPv6Prefix] sections for more configuration options.
693
694       IPv6MTUBytes=
695           Configures IPv6 maximum transmission unit (MTU). An integer greater
696           than or equal to 1280 bytes. When unset, the kernel's default will
697           be used.
698
699       Bridge=
700           The name of the bridge to add the link to. See systemd.netdev(5).
701
702       Bond=
703           The name of the bond to add the link to. See systemd.netdev(5).
704
705       VRF=
706           The name of the VRF to add the link to. See systemd.netdev(5).
707
708       VLAN=
709           The name of a VLAN to create on the link. See systemd.netdev(5).
710           This option may be specified more than once.
711
712       IPVLAN=
713           The name of a IPVLAN to create on the link. See systemd.netdev(5).
714           This option may be specified more than once.
715
716       MACVLAN=
717           The name of a MACVLAN to create on the link. See systemd.netdev(5).
718           This option may be specified more than once.
719
720       VXLAN=
721           The name of a VXLAN to create on the link. See systemd.netdev(5).
722           This option may be specified more than once.
723
724       Tunnel=
725           The name of a Tunnel to create on the link. See systemd.netdev(5).
726           This option may be specified more than once.
727
728       MACsec=
729           The name of a MACsec device to create on the link. See
730           systemd.netdev(5). This option may be specified more than once.
731
732       ActiveSlave=
733           Takes a boolean. Specifies the new active slave. The "ActiveSlave="
734           option is only valid for following modes: "active-backup",
735           "balance-alb" and "balance-tlb". Defaults to false.
736
737       PrimarySlave=
738           Takes a boolean. Specifies which slave is the primary device. The
739           specified device will always be the active slave while it is
740           available. Only when the primary is off-line will alternate devices
741           be used. This is useful when one slave is preferred over another,
742           e.g. when one slave has higher throughput than another. The
743           "PrimarySlave=" option is only valid for following modes:
744           "active-backup", "balance-alb" and "balance-tlb". Defaults to
745           false.
746
747       ConfigureWithoutCarrier=
748           Takes a boolean. Allows networkd to configure a specific link even
749           if it has no carrier. Defaults to false. If IgnoreCarrierLoss= is
750           not explicitly set, it will default to this value.
751
752       IgnoreCarrierLoss=
753           Takes a boolean. Allows networkd to retain both the static and
754           dynamic configuration of the interface even if its carrier is lost.
755           When unset, the value specified with ConfigureWithoutCarrier= is
756           used.
757
758       Xfrm=
759           The name of the xfrm to create on the link. See systemd.netdev(5).
760           This option may be specified more than once.
761
762       KeepConfiguration=
763           Takes a boolean or one of "static", "dhcp-on-stop", "dhcp". When
764           "static", systemd-networkd will not drop static addresses and
765           routes on starting up process. When set to "dhcp-on-stop",
766           systemd-networkd will not drop addresses and routes on stopping the
767           daemon. When "dhcp", the addresses and routes provided by a DHCP
768           server will never be dropped even if the DHCP lease expires. This
769           is contrary to the DHCP specification, but may be the best choice
770           if, e.g., the root filesystem relies on this connection. The
771           setting "dhcp" implies "dhcp-on-stop", and "yes" implies "dhcp" and
772           "static". Defaults to "no".
773

[ADDRESS] SECTION OPTIONS

775       An [Address] section accepts the following keys. Specify several
776       [Address] sections to configure several addresses.
777
778       Address=
779           As in the [Network] section. This key is mandatory. Each [Address]
780           section can contain one Address= setting.
781
782       Peer=
783           The peer address in a point-to-point connection. Accepts the same
784           format as the Address= key.
785
786       Broadcast=
787           The broadcast address, which must be in the format described in
788           inet_pton(3). This key only applies to IPv4 addresses. If it is not
789           given, it is derived from the Address= key.
790
791       Label=
792           An address label.
793
794       PreferredLifetime=
795           Allows the default "preferred lifetime" of the address to be
796           overridden. Only three settings are accepted: "forever" or
797           "infinity" which is the default and means that the address never
798           expires, and "0" which means that the address is considered
799           immediately "expired" and will not be used, unless explicitly
800           requested. A setting of PreferredLifetime=0 is useful for addresses
801           which are added to be used only by a specific application, which is
802           then configured to use them explicitly.
803
804       Scope=
805           The scope of the address, which can be "global", "link" or "host"
806           or an unsigned integer in the range 0—255. Defaults to "global".
807
808       HomeAddress=
809           Takes a boolean. Designates this address the "home address" as
810           defined in RFC 6275[10]. Supported only on IPv6. Defaults to false.
811
812       DuplicateAddressDetection=
813           Takes one of "ipv4", "ipv6", "both", "none". When "ipv4", performs
814           IPv4 Duplicate Address Detection. See RFC 5224[11]. When "ipv6",
815           performs IPv6 Duplicate Address Detection. See RFC 4862[12].
816           Defaults to "ipv6".
817
818       ManageTemporaryAddress=
819           Takes a boolean. If true the kernel manage temporary addresses
820           created from this one as template on behalf of Privacy Extensions
821           RFC 3041[13]. For this to become active, the use_tempaddr sysctl
822           setting has to be set to a value greater than zero. The given
823           address needs to have a prefix length of 64. This flag allows using
824           privacy extensions in a manually configured network, just like if
825           stateless auto-configuration was active. Defaults to false.
826
827       AddPrefixRoute=
828           Takes a boolean. When true, the prefix route for the address is
829           automatically added. Defaults to true.
830
831       AutoJoin=
832           Takes a boolean. Joining multicast group on ethernet level via ip
833           maddr command would not work if we have an Ethernet switch that
834           does IGMP snooping since the switch would not replicate multicast
835           packets on ports that did not have IGMP reports for the multicast
836           addresses. Linux vxlan interfaces created via ip link add vxlan or
837           networkd's netdev kind vxlan have the group option that enables
838           then to do the required join. By extending ip address command with
839           option "autojoin" we can get similar functionality for openvswitch
840           (OVS) vxlan interfaces as well as other tunneling mechanisms that
841           need to receive multicast traffic. Defaults to "no".
842

[NEIGHBOR] SECTION OPTIONS

844       A [Neighbor] section accepts the following keys. The neighbor section
845       adds a permanent, static entry to the neighbor table (IPv6) or ARP
846       table (IPv4) for the given hardware address on the links matched for
847       the network. Specify several [Neighbor] sections to configure several
848       static neighbors.
849
850       Address=
851           The IP address of the neighbor.
852
853       LinkLayerAddress=
854           The link layer address (MAC address or IP address) of the neighbor.
855

[IPV6ADDRESSLABEL] SECTION OPTIONS

857       An [IPv6AddressLabel] section accepts the following keys. Specify
858       several [IPv6AddressLabel] sections to configure several address
859       labels. IPv6 address labels are used for address selection. See RFC
860       3484[14]. Precedence is managed by userspace, and only the label itself
861       is stored in the kernel.
862
863       Label=
864           The label for the prefix, an unsigned integer in the range
865           0–4294967294. 0xffffffff is reserved. This setting is mandatory.
866
867       Prefix=
868           IPv6 prefix is an address with a prefix length, separated by a
869           slash "/" character. This key is mandatory.
870

[ROUTINGPOLICYRULE] SECTION OPTIONS

872       An [RoutingPolicyRule] section accepts the following keys. Specify
873       several [RoutingPolicyRule] sections to configure several rules.
874
875       TypeOfService=
876           Takes a number between 0 and 255 that specifies the type of service
877           to match.
878
879       From=
880           Specifies the source address prefix to match. Possibly followed by
881           a slash and the prefix length.
882
883       To=
884           Specifies the destination address prefix to match. Possibly
885           followed by a slash and the prefix length.
886
887       FirewallMark=
888           Specifies the iptables firewall mark value to match (a number
889           between 1 and 4294967295).
890
891       Table=
892           Specifies the routing table identifier to lookup if the rule
893           selector matches. Takes one of "default", "main", and "local", or a
894           number between 1 and 4294967295. Defaults to "main".
895
896       Priority=
897           Specifies the priority of this rule.  Priority= is an unsigned
898           integer. Higher number means lower priority, and rules get
899           processed in order of increasing number.
900
901       IncomingInterface=
902           Specifies incoming device to match. If the interface is loopback,
903           the rule only matches packets originating from this host.
904
905       OutgoingInterface=
906           Specifies the outgoing device to match. The outgoing interface is
907           only available for packets originating from local sockets that are
908           bound to a device.
909
910       SourcePort=
911           Specifies the source IP port or IP port range match in forwarding
912           information base (FIB) rules. A port range is specified by the
913           lower and upper port separated by a dash. Defaults to unset.
914
915       DestinationPort=
916           Specifies the destination IP port or IP port range match in
917           forwarding information base (FIB) rules. A port range is specified
918           by the lower and upper port separated by a dash. Defaults to unset.
919
920       IPProtocol=
921           Specifies the IP protocol to match in forwarding information base
922           (FIB) rules. Takes IP protocol name such as "tcp", "udp" or "sctp",
923           or IP protocol number such as "6" for "tcp" or "17" for "udp".
924           Defaults to unset.
925
926       InvertRule=
927           A boolean. Specifies whether the rule is to be inverted. Defaults
928           to false.
929
930       Family=
931           Takes a special value "ipv4", "ipv6", or "both". By default, the
932           address family is determined by the address specified in To= or
933           From=. If neither To= nor From= are specified, then defaults to
934           "ipv4".
935
936       User=
937           Takes a username, a user ID, or a range of user IDs separated by a
938           dash. Defaults to unset.
939
940       SuppressPrefixLength=
941           Takes a number N in the range 0-128 and rejects routing decisions
942           that have a prefix length of N or less. Defaults to unset.
943

[NEXTHOP] SECTION OPTIONS

945       The [NextHop] section is used to manipulate entries in the kernel's
946       "nexthop" tables. The [NextHop] section accepts the following keys.
947       Specify several [NextHop] sections to configure several hops.
948
949       Gateway=
950           As in the [Network] section. This is mandatory.
951
952       Id=
953           The id of the nexthop (an unsigned integer). If unspecified or '0'
954           then automatically chosen by kernel.
955

[ROUTE] SECTION OPTIONS

957       The [Route] section accepts the following keys. Specify several [Route]
958       sections to configure several routes.
959
960       Gateway=
961           Takes the gateway address or special value "_dhcp". If "_dhcp",
962           then the gateway address provided by DHCP (or in the IPv6 case,
963           provided by IPv6 RA) is used.
964
965       GatewayOnLink=
966           Takes a boolean. If set to true, the kernel does not have to check
967           if the gateway is reachable directly by the current machine (i.e.,
968           the kernel does not need to check if the gateway is attached to the
969           local network), so that we can insert the route in the kernel table
970           without it being complained about. Defaults to "no".
971
972       Destination=
973           The destination prefix of the route. Possibly followed by a slash
974           and the prefix length. If omitted, a full-length host route is
975           assumed.
976
977       Source=
978           The source prefix of the route. Possibly followed by a slash and
979           the prefix length. If omitted, a full-length host route is assumed.
980
981       Metric=
982           The metric of the route (an unsigned integer).
983
984       IPv6Preference=
985           Specifies the route preference as defined in RFC 4191[15] for
986           Router Discovery messages. Which can be one of "low" the route has
987           a lowest priority, "medium" the route has a default priority or
988           "high" the route has a highest priority.
989
990       Scope=
991           The scope of the route, which can be "global", "site", "link",
992           "host", or "nowhere". For IPv4 route, defaults to "host" if Type=
993           is "local" or "nat", and "link" if Type= is "broadcast",
994           "multicast", or "anycast". In other cases, defaults to "global".
995
996       PreferredSource=
997           The preferred source address of the route. The address must be in
998           the format described in inet_pton(3).
999
1000       Table=
1001           The table identifier for the route. Takes "default", "main",
1002           "local" or a number between 1 and 4294967295. The table can be
1003           retrieved using ip route show table num. If unset and Type= is
1004           "local", "broadcast", "anycast", or "nat", then "local" is used. In
1005           other cases, defaults to "main".
1006
1007       Protocol=
1008           The protocol identifier for the route. Takes a number between 0 and
1009           255 or the special values "kernel", "boot", "static", "ra" and
1010           "dhcp". Defaults to "static".
1011
1012       Type=
1013           Specifies the type for the route. Takes one of "unicast", "local",
1014           "broadcast", "anycast", "multicast", "blackhole", "unreachable",
1015           "prohibit", "throw", "nat", and "xresolve". If "unicast", a regular
1016           route is defined, i.e. a route indicating the path to take to a
1017           destination network address. If "blackhole", packets to the defined
1018           route are discarded silently. If "unreachable", packets to the
1019           defined route are discarded and the ICMP message "Host Unreachable"
1020           is generated. If "prohibit", packets to the defined route are
1021           discarded and the ICMP message "Communication Administratively
1022           Prohibited" is generated. If "throw", route lookup in the current
1023           routing table will fail and the route selection process will return
1024           to Routing Policy Database (RPDB). Defaults to "unicast".
1025
1026       InitialCongestionWindow=
1027           The TCP initial congestion window is used during the start of a TCP
1028           connection. During the start of a TCP session, when a client
1029           requests a resource, the server's initial congestion window
1030           determines how many data bytes will be sent during the initial
1031           burst of data. Takes a size in bytes between 1 and 4294967295 (2^32
1032           - 1). The usual suffixes K, M, G are supported and are understood
1033           to the base of 1024. When unset, the kernel's default will be used.
1034
1035       InitialAdvertisedReceiveWindow=
1036           The TCP initial advertised receive window is the amount of receive
1037           data (in bytes) that can initially be buffered at one time on a
1038           connection. The sending host can send only that amount of data
1039           before waiting for an acknowledgment and window update from the
1040           receiving host. Takes a size in bytes between 1 and 4294967295
1041           (2^32 - 1). The usual suffixes K, M, G are supported and are
1042           understood to the base of 1024. When unset, the kernel's default
1043           will be used.
1044
1045       QuickAck=
1046           Takes a boolean. When true enables TCP quick ack mode for the
1047           route. When unset, the kernel's default will be used.
1048
1049       FastOpenNoCookie=
1050           Takes a boolean. When true enables TCP fastopen without a cookie on
1051           a per-route basis. When unset, the kernel's default will be used.
1052
1053       TTLPropagate=
1054           Takes a boolean. When true enables TTL propagation at Label
1055           Switched Path (LSP) egress. When unset, the kernel's default will
1056           be used.
1057
1058       MTUBytes=
1059           The maximum transmission unit in bytes to set for the route. The
1060           usual suffixes K, M, G, are supported and are understood to the
1061           base of 1024.
1062
1063           Note that if IPv6 is enabled on the interface, and the MTU is
1064           chosen below 1280 (the minimum MTU for IPv6) it will automatically
1065           be increased to this value.
1066
1067       IPServiceType=
1068           Takes string; "CS6" or "CS4". Used to set IP service type to CS6
1069           (network control) or CS4 (Realtime). Defaults to CS6.
1070
1071       MultiPathRoute=address[@name] [weight]
1072           Configures multipath route. Multipath routing is the technique of
1073           using multiple alternative paths through a network. Takes gateway
1074           address. Optionally, takes a network interface name or index
1075           separated with "@", and a weight in 1..256 for this multipath route
1076           separated with whitespace. This setting can be specified multiple
1077           times. If an empty string is assigned, then the all previous
1078           assignments are cleared.
1079

[DHCPV4] SECTION OPTIONS

1081       The [DHCPv4] section configures the DHCPv4 client, if it is enabled
1082       with the DHCP= setting described above:
1083
1084       UseDNS=
1085           When true (the default), the DNS servers received from the DHCP
1086           server will be used.
1087
1088           This corresponds to the nameserver option in resolv.conf(5).
1089
1090       RoutesToDNS=
1091           When true, the routes to the DNS servers received from the DHCP
1092           server will be configured. When UseDNS= is disabled, this setting
1093           is ignored. Defaults to false.
1094
1095       UseNTP=
1096           When true (the default), the NTP servers received from the DHCP
1097           server will be used by systemd-timesyncd.service.
1098
1099       UseSIP=
1100           When true (the default), the SIP servers received from the DHCP
1101           server will be collected and made available to client programs.
1102
1103       UseMTU=
1104           When true, the interface maximum transmission unit from the DHCP
1105           server will be used on the current link. If MTUBytes= is set, then
1106           this setting is ignored. Defaults to false.
1107
1108       Anonymize=
1109           Takes a boolean. When true, the options sent to the DHCP server
1110           will follow the RFC 7844[16] (Anonymity Profiles for DHCP Clients)
1111           to minimize disclosure of identifying information. Defaults to
1112           false.
1113
1114           This option should only be set to true when MACAddressPolicy= is
1115           set to "random" (see systemd.link(5)).
1116
1117           Note that this configuration will overwrite others. In concrete,
1118           the following variables will be ignored: SendHostname=,
1119           ClientIdentifier=, UseRoutes=, UseMTU=, VendorClassIdentifier=,
1120           UseTimezone=.
1121
1122           With this option enabled DHCP requests will mimic those generated
1123           by Microsoft Windows, in order to reduce the ability to fingerprint
1124           and recognize installations. This means DHCP request sizes will
1125           grow and lease data will be more comprehensive than normally,
1126           though most of the requested data is not actually used.
1127
1128       SendHostname=
1129           When true (the default), the machine's hostname will be sent to the
1130           DHCP server. Note that the machine's hostname must consist only of
1131           7-bit ASCII lower-case characters and no spaces or dots, and be
1132           formatted as a valid DNS domain name. Otherwise, the hostname is
1133           not sent even if this is set to true.
1134
1135       MUDURL=
1136           When configured, the Manufacturer Usage Descriptions (MUD) URL will
1137           be sent to the DHCPv4 server. Takes an URL of length up to 255
1138           characters. A superficial verification that the string is a valid
1139           URL will be performed. DHCPv4 clients are intended to have at most
1140           one MUD URL associated with them. See RFC 8520[17].
1141
1142       UseHostname=
1143           When true (the default), the hostname received from the DHCP server
1144           will be set as the transient hostname of the system.
1145
1146       Hostname=
1147           Use this value for the hostname which is sent to the DHCP server,
1148           instead of machine's hostname. Note that the specified hostname
1149           must consist only of 7-bit ASCII lower-case characters and no
1150           spaces or dots, and be formatted as a valid DNS domain name.
1151
1152       UseDomains=
1153           Takes a boolean, or the special value "route". When true, the
1154           domain name received from the DHCP server will be used as DNS
1155           search domain over this link, similar to the effect of the Domains=
1156           setting. If set to "route", the domain name received from the DHCP
1157           server will be used for routing DNS queries only, but not for
1158           searching, similar to the effect of the Domains= setting when the
1159           argument is prefixed with "~". Defaults to false.
1160
1161           It is recommended to enable this option only on trusted networks,
1162           as setting this affects resolution of all hostnames, in particular
1163           of single-label names. It is generally safer to use the supplied
1164           domain only as routing domain, rather than as search domain, in
1165           order to not have it affect local resolution of single-label names.
1166
1167           When set to true, this setting corresponds to the domain option in
1168           resolv.conf(5).
1169
1170       UseRoutes=
1171           When true (the default), the static routes will be requested from
1172           the DHCP server and added to the routing table with a metric of
1173           1024, and a scope of "global", "link" or "host", depending on the
1174           route's destination and gateway. If the destination is on the local
1175           host, e.g., 127.x.x.x, or the same as the link's own address, the
1176           scope will be set to "host". Otherwise if the gateway is null (a
1177           direct route), a "link" scope will be used. For anything else,
1178           scope defaults to "global".
1179
1180       UseGateway=
1181           When true, the gateway will be requested from the DHCP server and
1182           added to the routing table with a metric of 1024, and a scope of
1183           "link". When unset, the value specified with UseRoutes= is used.
1184
1185       UseTimezone=
1186           When true, the timezone received from the DHCP server will be set
1187           as timezone of the local system. Defaults to "no".
1188
1189       ClientIdentifier=
1190           The DHCPv4 client identifier to use. Takes one of "mac", "duid" or
1191           "duid-only". If set to "mac", the MAC address of the link is used.
1192           If set to "duid", an RFC4361-compliant Client ID, which is the
1193           combination of IAID and DUID (see below), is used. If set to
1194           "duid-only", only DUID is used, this may not be RFC compliant, but
1195           some setups may require to use this. Defaults to "duid".
1196
1197       VendorClassIdentifier=
1198           The vendor class identifier used to identify vendor type and
1199           configuration.
1200
1201       UserClass=
1202           A DHCPv4 client can use UserClass option to identify the type or
1203           category of user or applications it represents. The information
1204           contained in this option is a string that represents the user class
1205           of which the client is a member. Each class sets an identifying
1206           string of information to be used by the DHCP service to classify
1207           clients. Takes a whitespace-separated list of strings.
1208
1209       MaxAttempts=
1210           Specifies how many times the DHCPv4 client configuration should be
1211           attempted. Takes a number or "infinity". Defaults to "infinity".
1212           Note that the time between retries is increased exponentially, so
1213           the network will not be overloaded even if this number is high.
1214
1215       DUIDType=
1216           Override the global DUIDType setting for this network. See
1217           networkd.conf(5) for a description of possible values.
1218
1219       DUIDRawData=
1220           Override the global DUIDRawData setting for this network. See
1221           networkd.conf(5) for a description of possible values.
1222
1223       IAID=
1224           The DHCP Identity Association Identifier (IAID) for the interface,
1225           a 32-bit unsigned integer.
1226
1227       RequestBroadcast=
1228           Request the server to use broadcast messages before the IP address
1229           has been configured. This is necessary for devices that cannot
1230           receive RAW packets, or that cannot receive packets at all before
1231           an IP address has been configured. On the other hand, this must not
1232           be enabled on networks where broadcasts are filtered out.
1233
1234       RouteMetric=
1235           Set the routing metric for routes specified by the DHCP server.
1236           Defaults to 1024.
1237
1238       RouteTable=num
1239           The table identifier for DHCP routes (a number between 1 and
1240           4294967295, or 0 to unset). The table can be retrieved using ip
1241           route show table num.
1242
1243           When used in combination with VRF=, the VRF's routing table is used
1244           when this parameter is not specified.
1245
1246       RouteMTUBytes=
1247           Specifies the MTU for the DHCP routes. Please see the [Route]
1248           section for further details.
1249
1250       ListenPort=
1251           Allow setting custom port for the DHCP client to listen on.
1252
1253       FallbackLeaseLifetimeSec=
1254           Allows to set DHCPv4 lease lifetime when DHCPv4 server does not
1255           send the lease lifetime. Takes one of "forever" or "infinity" means
1256           that the address never expires. Defaults to unset.
1257
1258       SendRelease=
1259           When true, the DHCPv4 client sends a DHCP release packet when it
1260           stops. Defaults to true.
1261
1262       SendDecline=
1263           A boolean. When "true", the DHCPv4 client receives the IP address
1264           from the DHCP server. After a new IP is received, the DHCPv4 client
1265           performs IPv4 Duplicate Address Detection. If duplicate use is
1266           detected, the DHCPv4 client rejects the IP by sending a DHCPDECLINE
1267           packet and tries to obtain an IP address again. See RFC 5224[11].
1268           Defaults to "unset".
1269
1270       DenyList=
1271           A whitespace-separated list of IPv4 addresses. DHCP offers from
1272           servers in the list are rejected. Note that if AllowList= is
1273           configured then DenyList= is ignored.
1274
1275       AllowList=
1276           A whitespace-separated list of IPv4 addresses. DHCP offers from
1277           servers in the list are accepted.
1278
1279       RequestOptions=
1280           When configured, allows to set arbitrary request options in the
1281           DHCPv4 request options list and will be sent to the DHCPV4 server.
1282           A whitespace-separated list of integers in the range 1..254.
1283           Defaults to unset.
1284
1285       SendOption=
1286           Send an arbitrary raw option in the DHCPv4 request. Takes a DHCP
1287           option number, data type and data separated with a colon
1288           ("option:type:value"). The option number must be an integer in the
1289           range 1..254. The type takes one of "uint8", "uint16", "uint32",
1290           "ipv4address", or "string". Special characters in the data string
1291           may be escaped using C-style escapes[18]. This setting can be
1292           specified multiple times. If an empty string is specified, then all
1293           options specified earlier are cleared. Defaults to unset.
1294
1295       SendVendorOption=
1296           Send an arbitrary vendor option in the DHCPv4 request. Takes a DHCP
1297           option number, data type and data separated with a colon
1298           ("option:type:value"). The option number must be an integer in the
1299           range 1..254. The type takes one of "uint8", "uint16", "uint32",
1300           "ipv4address", or "string". Special characters in the data string
1301           may be escaped using C-style escapes[18]. This setting can be
1302           specified multiple times. If an empty string is specified, then all
1303           options specified earlier are cleared. Defaults to unset.
1304

[DHCPV6] SECTION OPTIONS

1306       The [DHCPv6] section configures the DHCPv6 client, if it is enabled
1307       with the DHCP= setting described above, or invoked by the IPv6 Router
1308       Advertisement:
1309
1310       UseDNS=, UseNTP=
1311           As in the [DHCPv4] section.
1312
1313       RouteMetric=
1314           Set the routing metric for routes specified by the DHCP server.
1315           Defaults to 1024.
1316
1317       RapidCommit=
1318           Takes a boolean. The DHCPv6 client can obtain configuration
1319           parameters from a DHCPv6 server through a rapid two-message
1320           exchange (solicit and reply). When the rapid commit option is
1321           enabled by both the DHCPv6 client and the DHCPv6 server, the
1322           two-message exchange is used, rather than the default four-message
1323           exchange (solicit, advertise, request, and reply). The two-message
1324           exchange provides faster client configuration and is beneficial in
1325           environments in which networks are under a heavy load. See RFC
1326           3315[19] for details. Defaults to true.
1327
1328       MUDURL=
1329           When configured, the Manufacturer Usage Descriptions (MUD) URL will
1330           be sent to the DHCPV6 server. Takes an URL of length up to 255
1331           characters. A superficial verification that the string is a valid
1332           URL will be performed. DHCPv6 clients are intended to have at most
1333           one MUD URL associated with them. See RFC 8520[17].
1334
1335       RequestOptions=
1336           When configured, allows to set arbitrary request options in the
1337           DHCPv6 request options list and will sent to the DHCPV6 server. A
1338           whitespace-separated list of integers in the range 1..254. Defaults
1339           to unset.
1340
1341       SendVendorOption=
1342           Send an arbitrary vendor option in the DHCPv6 request. Takes an
1343           enterprise identifier, DHCP option number, data type, and data
1344           separated with a colon ("enterprise identifier:option:type:
1345           value"). Enterprise identifier is an unsigned integer in the range
1346           1–4294967294. The option number must be an integer in the range
1347           1–254. Data type takes one of "uint8", "uint16", "uint32",
1348           "ipv4address", "ipv6address", or "string". Special characters in
1349           the data string may be escaped using C-style escapes[18]. This
1350           setting can be specified multiple times. If an empty string is
1351           specified, then all options specified earlier are cleared. Defaults
1352           to unset.
1353
1354       ForceDHCPv6PDOtherInformation=
1355           Takes a boolean that enforces DHCPv6 stateful mode when the 'Other
1356           information' bit is set in Router Advertisement messages. By
1357           default setting only the 'O' bit in Router Advertisements makes
1358           DHCPv6 request network information in a stateless manner using a
1359           two-message Information Request and Information Reply message
1360           exchange.  RFC 7084[20], requirement WPD-4, updates this behavior
1361           for a Customer Edge router so that stateful DHCPv6 Prefix
1362           Delegation is also requested when only the 'O' bit is set in Router
1363           Advertisements. This option enables such a CE behavior as it is
1364           impossible to automatically distinguish the intention of the 'O'
1365           bit otherwise. By default this option is set to 'false', enable it
1366           if no prefixes are delegated when the device should be acting as a
1367           CE router.
1368
1369       PrefixDelegationHint=
1370           Takes an IPv6 address with prefix length in the same format as the
1371           Address= in the [Network] section. The DHCPv6 client will include a
1372           prefix hint in the DHCPv6 solicitation sent to the server. The
1373           prefix length must be in the range 1–128. Defaults to unset.
1374
1375       WithoutRA=
1376           Allows DHCPv6 client to start without router advertisements's
1377           managed or other address configuration flag. Takes one of "solicit"
1378           or "information-request". Defaults to unset.
1379
1380       SendOption=
1381           As in the [DHCPv4] section, however because DHCPv6 uses 16-bit
1382           fields to store option numbers, the option number is an integer in
1383           the range 1..65536.
1384
1385       UserClass=
1386           A DHCPv6 client can use User Class option to identify the type or
1387           category of user or applications it represents. The information
1388           contained in this option is a string that represents the user class
1389           of which the client is a member. Each class sets an identifying
1390           string of information to be used by the DHCP service to classify
1391           clients. Special characters in the data string may be escaped using
1392           C-style escapes[18]. This setting can be specified multiple times.
1393           If an empty string is specified, then all options specified earlier
1394           are cleared. Takes a whitespace-separated list of strings. Note
1395           that currently NUL bytes are not allowed.
1396
1397       VendorClass=
1398           A DHCPv6 client can use VendorClass option to identify the vendor
1399           that manufactured the hardware on which the client is running. The
1400           information contained in the data area of this option is contained
1401           in one or more opaque fields that identify details of the hardware
1402           configuration. Takes a whitespace-separated list of strings.
1403

[DHCPV6PREFIXDELEGATION] SECTION OPTIONS

1405       The [DHCPv6PrefixDelegation] section configures delegated prefix
1406       assigned by DHCPv6 server. The settings in this section are used only
1407       when IPv6PrefixDelegation= setting is enabled, or set to "dhcpv6".
1408
1409       SubnetId=
1410           Configure a specific subnet ID on the interface from a (previously)
1411           received prefix delegation. You can either set "auto" (the default)
1412           or a specific subnet ID (as defined in RFC 4291[21], section
1413           2.5.4), in which case the allowed value is hexadecimal, from 0 to
1414           0x7fffffffffffffff inclusive. This option is only effective when
1415           used together with IPv6PrefixDelegation= and the corresponding
1416           configuration on the upstream interface.
1417
1418       Assign=
1419           Takes a boolean. Specifies whether to add an address from the
1420           delegated prefixes which are received from the WAN interface by the
1421           IPv6PrefixDelegation=. When true (on LAN interfce), the EUI-64
1422           algorithm will be used to form an interface identifier from the
1423           delegated prefixes. Defaults to true.
1424
1425       Token=
1426           Specifies an optional address generation mode for Assign=. Takes an
1427           IPv6 address. When set, the lower bits of the supplied address are
1428           combined with the upper bits of a delegatad prefix received from
1429           the WAN interface by the IPv6PrefixDelegation= prefixes to form a
1430           complete address.
1431

[IPV6ACCEPTRA] SECTION OPTIONS

1433       The [IPv6AcceptRA] section configures the IPv6 Router Advertisement
1434       (RA) client, if it is enabled with the IPv6AcceptRA= setting described
1435       above:
1436
1437       UseDNS=
1438           When true (the default), the DNS servers received in the Router
1439           Advertisement will be used.
1440
1441           This corresponds to the nameserver option in resolv.conf(5).
1442
1443       UseDomains=
1444           Takes a boolean, or the special value "route". When true, the
1445           domain name received via IPv6 Router Advertisement (RA) will be
1446           used as DNS search domain over this link, similar to the effect of
1447           the Domains= setting. If set to "route", the domain name received
1448           via IPv6 RA will be used for routing DNS queries only, but not for
1449           searching, similar to the effect of the Domains= setting when the
1450           argument is prefixed with "~". Defaults to false.
1451
1452           It is recommended to enable this option only on trusted networks,
1453           as setting this affects resolution of all hostnames, in particular
1454           of single-label names. It is generally safer to use the supplied
1455           domain only as routing domain, rather than as search domain, in
1456           order to not have it affect local resolution of single-label names.
1457
1458           When set to true, this setting corresponds to the domain option in
1459           resolv.conf(5).
1460
1461       RouteTable=num
1462           The table identifier for the routes received in the Router
1463           Advertisement (a number between 1 and 4294967295, or 0 to unset).
1464           The table can be retrieved using ip route show table num.
1465
1466       UseAutonomousPrefix=
1467           When true (the default), the autonomous prefix received in the
1468           Router Advertisement will be used and take precedence over any
1469           statically configured ones.
1470
1471       UseOnLinkPrefix=
1472           When true (the default), the onlink prefix received in the Router
1473           Advertisement will be used and take precedence over any statically
1474           configured ones.
1475
1476       DenyList=
1477           A whitespace-separated list of IPv6 prefixes. IPv6 prefixes
1478           supplied via router advertisements in the list are ignored.
1479
1480       DHCPv6Client=
1481           Takes a boolean, or the special value "always". When true or
1482           "always", the DHCPv6 client will be started when the RA has the
1483           managed or other information flag. If set to "always", the DHCPv6
1484           client will also be started in managed mode when neither managed
1485           nor other information flag is set in the RA. Defaults to true.
1486

[DHCPSERVER] SECTION OPTIONS

1488       The [DHCPServer] section contains settings for the DHCP server, if
1489       enabled via the DHCPServer= option described above:
1490
1491       PoolOffset=, PoolSize=
1492           Configures the pool of addresses to hand out. The pool is a
1493           contiguous sequence of IP addresses in the subnet configured for
1494           the server address, which does not include the subnet nor the
1495           broadcast address.  PoolOffset= takes the offset of the pool from
1496           the start of subnet, or zero to use the default value.  PoolSize=
1497           takes the number of IP addresses in the pool or zero to use the
1498           default value. By default, the pool starts at the first address
1499           after the subnet address and takes up the rest of the subnet,
1500           excluding the broadcast address. If the pool includes the server
1501           address (the default), this is reserved and not handed out to
1502           clients.
1503
1504       DefaultLeaseTimeSec=, MaxLeaseTimeSec=
1505           Control the default and maximum DHCP lease time to pass to clients.
1506           These settings take time values in seconds or another common time
1507           unit, depending on the suffix. The default lease time is used for
1508           clients that did not ask for a specific lease time. If a client
1509           asks for a lease time longer than the maximum lease time, it is
1510           automatically shortened to the specified time. The default lease
1511           time defaults to 1h, the maximum lease time to 12h. Shorter lease
1512           times are beneficial if the configuration data in DHCP leases
1513           changes frequently and clients shall learn the new settings with
1514           shorter latencies. Longer lease times reduce the generated DHCP
1515           network traffic.
1516
1517       EmitDNS=, DNS=
1518           EmitDNS= takes a boolean. Configures whether the DHCP leases handed
1519           out to clients shall contain DNS server information. Defaults to
1520           "yes". The DNS servers to pass to clients may be configured with
1521           the DNS= option, which takes a list of IPv4 addresses. If the
1522           EmitDNS= option is enabled but no servers configured, the servers
1523           are automatically propagated from an "uplink" interface that has
1524           appropriate servers set. The "uplink" interface is determined by
1525           the default route of the system with the highest priority. Note
1526           that this information is acquired at the time the lease is handed
1527           out, and does not take uplink interfaces into account that acquire
1528           DNS server information at a later point. If no suitable uplinkg
1529           interface is found the DNS server data from /etc/resolv.conf is
1530           used. Also, note that the leases are not refreshed if the uplink
1531           network configuration changes. To ensure clients regularly acquire
1532           the most current uplink DNS server information, it is thus
1533           advisable to shorten the DHCP lease time via MaxLeaseTimeSec=
1534           described above.
1535
1536       EmitNTP=, NTP=, EmitSIP=, SIP=, EmitPOP3=, POP3=, EmitSMTP=, SMTP=,
1537       EmitLPR=, LPR=
1538           Similar to the EmitDNS= and DNS= settings described above, these
1539           settings configure whether and what server information for the
1540           indicate protocol shall be emitted as part of the DHCP lease. The
1541           same syntax, propagation semantics and defaults apply as for
1542           EmitDNS= and DNS=.
1543
1544       EmitRouter=
1545           Similar to the EmitDNS= setting described above, this setting
1546           configures whether the DHCP lease should contain the router option.
1547           The same syntax, propagation semantics and defaults apply as for
1548           EmitDNS=.
1549
1550       EmitTimezone=, Timezone=
1551           Takes a boolean. Configures whether the DHCP leases handed out to
1552           clients shall contain timezone information. Defaults to "yes". The
1553           Timezone= setting takes a timezone string (such as "Europe/Berlin"
1554           or "UTC") to pass to clients. If no explicit timezone is set, the
1555           system timezone of the local host is propagated, as determined by
1556           the /etc/localtime symlink.
1557
1558       SendOption=
1559           Send a raw option with value via DHCPv4 server. Takes a DHCP option
1560           number, data type and data ("option:type:value"). The option number
1561           is an integer in the range 1..254. The type takes one of "uint8",
1562           "uint16", "uint32", "ipv4address", "ipv6address", or "string".
1563           Special characters in the data string may be escaped using C-style
1564           escapes[18]. This setting can be specified multiple times. If an
1565           empty string is specified, then all options specified earlier are
1566           cleared. Defaults to unset.
1567
1568       SendVendorOption=
1569           Send a vendor option with value via DHCPv4 server. Takes a DHCP
1570           option number, data type and data ("option:type:value"). The option
1571           number is an integer in the range 1..254. The type takes one of
1572           "uint8", "uint16", "uint32", "ipv4address", or "string". Special
1573           characters in the data string may be escaped using C-style
1574           escapes[18]. This setting can be specified multiple times. If an
1575           empty string is specified, then all options specified earlier are
1576           cleared. Defaults to unset.
1577

[IPV6PREFIXDELEGATION] SECTION OPTIONS

1579       The [IPv6PrefixDelegation] section contains settings for sending IPv6
1580       Router Advertisements and whether to act as a router, if enabled via
1581       the IPv6PrefixDelegation= option described above. IPv6 network prefixes
1582       are defined with one or more [IPv6Prefix] sections.
1583
1584       Managed=, OtherInformation=
1585           Takes a boolean. Controls whether a DHCPv6 server is used to
1586           acquire IPv6 addresses on the network link when Managed= is set to
1587           "true" or if only additional network information can be obtained
1588           via DHCPv6 for the network link when OtherInformation= is set to
1589           "true". Both settings default to "false", which means that a DHCPv6
1590           server is not being used.
1591
1592       RouterLifetimeSec=
1593           Takes a timespan. Configures the IPv6 router lifetime in seconds.
1594           When set to 0, the host is not acting as a router. Defaults to 30
1595           minutes.
1596
1597       RouterPreference=
1598           Configures IPv6 router preference if RouterLifetimeSec= is
1599           non-zero. Valid values are "high", "medium" and "low", with
1600           "normal" and "default" added as synonyms for "medium" just to make
1601           configuration easier. See RFC 4191[15] for details. Defaults to
1602           "medium".
1603
1604       EmitDNS=, DNS=
1605           DNS= specifies a list of recursive DNS server IPv6 addresses that
1606           are distributed via Router Advertisement messages when EmitDNS= is
1607           true.  DNS= also takes special value "_link_local"; in that case
1608           the IPv6 link local address is distributed. If DNS= is empty, DNS
1609           servers are read from the [Network] section. If the [Network]
1610           section does not contain any DNS servers either, DNS servers from
1611           the uplink with the highest priority default route are used. When
1612           EmitDNS= is false, no DNS server information is sent in Router
1613           Advertisement messages.  EmitDNS= defaults to true.
1614
1615       EmitDomains=, Domains=
1616           A list of DNS search domains distributed via Router Advertisement
1617           messages when EmitDomains= is true. If Domains= is empty, DNS
1618           search domains are read from the [Network] section. If the
1619           [Network] section does not contain any DNS search domains either,
1620           DNS search domains from the uplink with the highest priority
1621           default route are used. When EmitDomains= is false, no DNS search
1622           domain information is sent in Router Advertisement messages.
1623           EmitDomains= defaults to true.
1624
1625       DNSLifetimeSec=
1626           Lifetime in seconds for the DNS server addresses listed in DNS= and
1627           search domains listed in Domains=.
1628

[IPV6PREFIX] SECTION OPTIONS

1630       One or more [IPv6Prefix] sections contain the IPv6 prefixes that are
1631       announced via Router Advertisements. See RFC 4861[22] for further
1632       details.
1633
1634       AddressAutoconfiguration=, OnLink=
1635           Takes a boolean to specify whether IPv6 addresses can be
1636           autoconfigured with this prefix and whether the prefix can be used
1637           for onlink determination. Both settings default to "true" in order
1638           to ease configuration.
1639
1640       Prefix=
1641           The IPv6 prefix that is to be distributed to hosts. Similarly to
1642           configuring static IPv6 addresses, the setting is configured as an
1643           IPv6 prefix and its prefix length, separated by a "/" character.
1644           Use multiple [IPv6Prefix] sections to configure multiple IPv6
1645           prefixes since prefix lifetimes, address autoconfiguration and
1646           onlink status may differ from one prefix to another.
1647
1648       PreferredLifetimeSec=, ValidLifetimeSec=
1649           Preferred and valid lifetimes for the prefix measured in seconds.
1650           PreferredLifetimeSec= defaults to 604800 seconds (one week) and
1651           ValidLifetimeSec= defaults to 2592000 seconds (30 days).
1652
1653       Assign=
1654           Takes a boolean. When true, adds an address from the prefix.
1655           Default to false.
1656

[IPV6ROUTEPREFIX] SECTION OPTIONS

1658       One or more [IPv6RoutePrefix] sections contain the IPv6 prefix routes
1659       that are announced via Router Advertisements. See RFC 4191[15] for
1660       further details.
1661
1662       Route=
1663           The IPv6 route that is to be distributed to hosts. Similarly to
1664           configuring static IPv6 routes, the setting is configured as an
1665           IPv6 prefix routes and its prefix route length, separated by a "/"
1666           character. Use multiple [IPv6PrefixRoutes] sections to configure
1667           multiple IPv6 prefix routes.
1668
1669       LifetimeSec=
1670           Lifetime for the route prefix measured in seconds.  LifetimeSec=
1671           defaults to 604800 seconds (one week).
1672

[BRIDGE] SECTION OPTIONS

1674       The [Bridge] section accepts the following keys:
1675
1676       UnicastFlood=
1677           Takes a boolean. Controls whether the bridge should flood traffic
1678           for which an FDB entry is missing and the destination is unknown
1679           through this port. When unset, the kernel's default will be used.
1680
1681       MulticastFlood=
1682           Takes a boolean. Controls whether the bridge should flood traffic
1683           for which an MDB entry is missing and the destination is unknown
1684           through this port. When unset, the kernel's default will be used.
1685
1686       MulticastToUnicast=
1687           Takes a boolean. Multicast to unicast works on top of the multicast
1688           snooping feature of the bridge. Which means unicast copies are only
1689           delivered to hosts which are interested in it. When unset, the
1690           kernel's default will be used.
1691
1692       NeighborSuppression=
1693           Takes a boolean. Configures whether ARP and ND neighbor suppression
1694           is enabled for this port. When unset, the kernel's default will be
1695           used.
1696
1697       Learning=
1698           Takes a boolean. Configures whether MAC address learning is enabled
1699           for this port. When unset, the kernel's default will be used.
1700
1701       HairPin=
1702           Takes a boolean. Configures whether traffic may be sent back out of
1703           the port on which it was received. When this flag is false, then
1704           the bridge will not forward traffic back out of the receiving port.
1705           When unset, the kernel's default will be used.
1706
1707       UseBPDU=
1708           Takes a boolean. Configures whether STP Bridge Protocol Data Units
1709           will be processed by the bridge port. When unset, the kernel's
1710           default will be used.
1711
1712       FastLeave=
1713           Takes a boolean. This flag allows the bridge to immediately stop
1714           multicast traffic on a port that receives an IGMP Leave message. It
1715           is only used with IGMP snooping if enabled on the bridge. When
1716           unset, the kernel's default will be used.
1717
1718       AllowPortToBeRoot=
1719           Takes a boolean. Configures whether a given port is allowed to
1720           become a root port. Only used when STP is enabled on the bridge.
1721           When unset, the kernel's default will be used.
1722
1723       ProxyARP=
1724           Takes a boolean. Configures whether proxy ARP to be enabled on this
1725           port. When unset, the kernel's default will be used.
1726
1727       ProxyARPWiFi=
1728           Takes a boolean. Configures whether proxy ARP to be enabled on this
1729           port which meets extended requirements by IEEE 802.11 and Hotspot
1730           2.0 specifications. When unset, the kernel's default will be used.
1731
1732       MulticastRouter=
1733           Configures this port for having multicast routers attached. A port
1734           with a multicast router will receive all multicast traffic. Takes
1735           one of "no" to disable multicast routers on this port, "query" to
1736           let the system detect the presence of routers, "permanent" to
1737           permanently enable multicast traffic forwarding on this port, or
1738           "temporary" to enable multicast routers temporarily on this port,
1739           not depending on incoming queries. When unset, the kernel's default
1740           will be used.
1741
1742       Cost=
1743           Sets the "cost" of sending packets of this interface. Each port in
1744           a bridge may have a different speed and the cost is used to decide
1745           which link to use. Faster interfaces should have lower costs. It is
1746           an integer value between 1 and 65535.
1747
1748       Priority=
1749           Sets the "priority" of sending packets on this interface. Each port
1750           in a bridge may have a different priority which is used to decide
1751           which link to use. Lower value means higher priority. It is an
1752           integer value between 0 to 63. Networkd does not set any default,
1753           meaning the kernel default value of 32 is used.
1754

[BRIDGEFDB] SECTION OPTIONS

1756       The [BridgeFDB] section manages the forwarding database table of a port
1757       and accepts the following keys. Specify several [BridgeFDB] sections to
1758       configure several static MAC table entries.
1759
1760       MACAddress=
1761           As in the [Network] section. This key is mandatory.
1762
1763       Destination=
1764           Takes an IP address of the destination VXLAN tunnel endpoint.
1765
1766       VLANId=
1767           The VLAN ID for the new static MAC table entry. If omitted, no VLAN
1768           ID information is appended to the new static MAC table entry.
1769
1770       VNI=
1771           The VXLAN Network Identifier (or VXLAN Segment ID) to use to
1772           connect to the remote VXLAN tunnel endpoint. Takes a number in the
1773           range 1-16777215. Defaults to unset.
1774
1775       AssociatedWith=
1776           Specifies where the address is associated with. Takes one of "use",
1777           "self", "master" or "router".  "use" means the address is in use.
1778           User space can use this option to indicate to the kernel that the
1779           fdb entry is in use.  "self" means the address is associated with
1780           the port drivers fdb. Usually hardware.  "master" means the address
1781           is associated with master devices fdb.  "router" means the
1782           destination address is associated with a router. Note that it's
1783           valid if the referenced device is a VXLAN type device and has route
1784           shortcircuit enabled. Defaults to "self".
1785

[LLDP] SECTION OPTIONS

1787       The [LLDP] section manages the Link Layer Discovery Protocol (LLDP) and
1788       accepts the following keys.
1789
1790       MUDURL=
1791           Controls support for Ethernet LLDP packet's Manufacturer Usage
1792           Description (MUD). MUD is an embedded software standard defined by
1793           the IETF that allows IoT Device makers to advertise device
1794           specifications, including the intended communication patterns for
1795           their device when it connects to the network. The network can then
1796           use this intent to author a context-specific access policy, so the
1797           device functions only within those parameters. Takes an URL of
1798           length up to 255 characters. A superficial verification that the
1799           string is a valid URL will be performed. See RFC 8520[17] for
1800           details. The MUD URL received from the LLDP packets will be saved
1801           at the state files and can be read via
1802           sd_lldp_neighbor_get_mud_url() function.
1803

[CAN] SECTION OPTIONS

1805       The [CAN] section manages the Controller Area Network (CAN bus) and
1806       accepts the following keys:
1807
1808       BitRate=
1809           The bitrate of CAN device in bits per second. The usual SI prefixes
1810           (K, M) with the base of 1000 can be used here. Takes a number in
1811           the range 1..4294967295.
1812
1813       SamplePoint=
1814           Optional sample point in percent with one decimal (e.g.  "75%",
1815           "87.5%") or permille (e.g.  "875‰").
1816
1817       DataBitRate=, DataSamplePoint=
1818           The bitrate and sample point for the data phase, if CAN-FD is used.
1819           These settings are analogous to the BitRate= and SamplePoint= keys.
1820
1821       FDMode=
1822           Takes a boolean. When "yes", CAN-FD mode is enabled for the
1823           interface. Note, that a bitrate and optional sample point should
1824           also be set for the CAN-FD data phase using the DataBitRate= and
1825           DataSamplePoint= keys.
1826
1827       FDNonISO=
1828           Takes a boolean. When "yes", non-ISO CAN-FD mode is enabled for the
1829           interface. When unset, the kernel's default will be used.
1830
1831       RestartSec=
1832           Automatic restart delay time. If set to a non-zero value, a restart
1833           of the CAN controller will be triggered automatically in case of a
1834           bus-off condition after the specified delay time. Subsecond delays
1835           can be specified using decimals (e.g.  "0.1s") or a "ms" or "us"
1836           postfix. Using "infinity" or "0" will turn the automatic restart
1837           off. By default automatic restart is disabled.
1838
1839       Termination=
1840           Takes a boolean. When "yes", the termination resistor will be
1841           selected for the bias network. When unset, the kernel's default
1842           will be used.
1843
1844       TripleSampling=
1845           Takes a boolean. When "yes", three samples (instead of one) are
1846           used to determine the value of a received bit by majority rule.
1847           When unset, the kernel's default will be used.
1848
1849       ListenOnly=
1850           Takes a boolean. When "yes", listen-only mode is enabled. When the
1851           interface is in listen-only mode, the interface neither transmit
1852           CAN frames nor send ACK bit. Listen-only mode is important to debug
1853           CAN networks without interfering with the communication or
1854           acknowledge the CAN frame. When unset, the kernel's default will be
1855           used.
1856

[QDISC] SECTION OPTIONS

1858       The [QDisc] section manages the traffic control queueing discipline
1859       (qdisc).
1860
1861       Parent=
1862           Specifies the parent Queueing Discipline (qdisc). Takes one of
1863           "clsact" or "ingress". This is mandatory.
1864
1865       Handle=
1866           Configures the major number of unique identifier of the qdisc,
1867           known as the handle. Takes a hexadecimal number in the range
1868           0x1–0xffff. Defaults to unset.
1869

[NETWORKEMULATOR] SECTION OPTIONS

1871       The [NetworkEmulator] section manages the queueing discipline (qdisc)
1872       of the network emulator. It can be used to configure the kernel packet
1873       scheduler and simulate packet delay and loss for UDP or TCP
1874       applications, or limit the bandwidth usage of a particular service to
1875       simulate internet connections.
1876
1877       Parent=
1878           Configures the parent Queueing Discipline (qdisc). Takes one of
1879           "root", "clsact", "ingress" or a class identifier. The class
1880           identifier is specified as the major and minor numbers in
1881           hexadecimal in the range 0x1–Oxffff separated with a colon
1882           ("major:minor"). Defaults to "root".
1883
1884       Handle=
1885           Configures the major number of unique identifier of the qdisc,
1886           known as the handle. Takes a hexadecimal number in the range
1887           0x1–0xffff. Defaults to unset.
1888
1889       DelaySec=
1890           Specifies the fixed amount of delay to be added to all packets
1891           going out of the interface. Defaults to unset.
1892
1893       DelayJitterSec=
1894           Specifies the chosen delay to be added to the packets outgoing to
1895           the network interface. Defaults to unset.
1896
1897       PacketLimit=
1898           Specifies the maximum number of packets the qdisc may hold queued
1899           at a time. An unsigned integer in the range 0–4294967294. Defaults
1900           to 1000.
1901
1902       LossRate=
1903           Specifies an independent loss probability to be added to the
1904           packets outgoing from the network interface. Takes a percentage
1905           value, suffixed with "%". Defaults to unset.
1906
1907       DuplicateRate=
1908           Specifies that the chosen percent of packets is duplicated before
1909           queuing them. Takes a percentage value, suffixed with "%". Defaults
1910           to unset.
1911

[TOKENBUCKETFILTER] SECTION OPTIONS

1913       The [TokenBucketFilter] section manages the queueing discipline (qdisc)
1914       of token bucket filter (tbf).
1915
1916       Parent=
1917           Configures the parent Queueing Discipline (qdisc). Takes one of
1918           "root", "clsact", "ingress" or a class identifier. The class
1919           identifier is specified as the major and minor numbers in
1920           hexadecimal in the range 0x1–Oxffff separated with a colon
1921           ("major:minor"). Defaults to "root".
1922
1923       Handle=
1924           Configures the major number of unique identifier of the qdisc,
1925           known as the handle. Takes a hexadecimal number in the range
1926           0x1–0xffff. Defaults to unset.
1927
1928       LatencySec=
1929           Specifies the latency parameter, which specifies the maximum amount
1930           of time a packet can sit in the Token Bucket Filter (TBF). Defaults
1931           to unset.
1932
1933       LimitBytes=
1934           Takes the number of bytes that can be queued waiting for tokens to
1935           become available. When the size is suffixed with K, M, or G, it is
1936           parsed as Kilobytes, Megabytes, or Gigabytes, respectively, to the
1937           base of 1024. Defaults to unset.
1938
1939       BurstBytes=
1940           Specifies the size of the bucket. This is the maximum amount of
1941           bytes that tokens can be available for instantaneous transfer. When
1942           the size is suffixed with K, M, or G, it is parsed as Kilobytes,
1943           Megabytes, or Gigabytes, respectively, to the base of 1024.
1944           Defaults to unset.
1945
1946       Rate=
1947           Specifies the device specific bandwidth. When suffixed with K, M,
1948           or G, the specified bandwidth is parsed as Kilobits, Megabits, or
1949           Gigabits, respectively, to the base of 1000. Defaults to unset.
1950
1951       MPUBytes=
1952           The Minimum Packet Unit (MPU) determines the minimal token usage
1953           (specified in bytes) for a packet. When suffixed with K, M, or G,
1954           the specified size is parsed as Kilobytes, Megabytes, or Gigabytes,
1955           respectively, to the base of 1024. Defaults to zero.
1956
1957       PeakRate=
1958           Takes the maximum depletion rate of the bucket. When suffixed with
1959           K, M, or G, the specified size is parsed as Kilobits, Megabits, or
1960           Gigabits, respectively, to the base of 1000. Defaults to unset.
1961
1962       MTUBytes=
1963           Specifies the size of the peakrate bucket. When suffixed with K, M,
1964           or G, the specified size is parsed as Kilobytes, Megabytes, or
1965           Gigabytes, respectively, to the base of 1024. Defaults to unset.
1966

[PIE] SECTION OPTIONS

1968       The [PIE] section manages the queueing discipline (qdisc) of
1969       Proportional Integral controller-Enhanced (PIE).
1970
1971       Parent=
1972           Configures the parent Queueing Discipline (qdisc). Takes one of
1973           "root", "clsact", "ingress" or a class identifier. The class
1974           identifier is specified as the major and minor numbers in
1975           hexadecimal in the range 0x1–Oxffff separated with a colon
1976           ("major:minor"). Defaults to "root".
1977
1978       Handle=
1979           Configures the major number of unique identifier of the qdisc,
1980           known as the handle. Takes a hexadecimal number in the range
1981           0x1–0xffff. Defaults to unset.
1982
1983       PacketLimit=
1984           Specifies the hard limit on the queue size in number of packets.
1985           When this limit is reached, incoming packets are dropped. An
1986           unsigned integer in the range 1–4294967294. Defaults to unset and
1987           kernel's default is used.
1988

[STOCHASTICFAIRBLUE] SECTION OPTIONS

1990       The [StochasticFairBlue] section manages the queueing discipline
1991       (qdisc) of stochastic fair blue (sfb).
1992
1993       Parent=
1994           Configures the parent Queueing Discipline (qdisc). Takes one of
1995           "root", "clsact", "ingress" or a class identifier. The class
1996           identifier is specified as the major and minor numbers in
1997           hexadecimal in the range 0x1–Oxffff separated with a colon
1998           ("major:minor"). Defaults to "root".
1999
2000       Handle=
2001           Configures the major number of unique identifier of the qdisc,
2002           known as the handle. Takes a hexadecimal number in the range
2003           0x1–0xffff. Defaults to unset.
2004
2005       PacketLimit=
2006           Specifies the hard limit on the queue size in number of packets.
2007           When this limit is reached, incoming packets are dropped. An
2008           unsigned integer in the range 0–4294967294. Defaults to unset and
2009           kernel's default is used.
2010

[STOCHASTICFAIRNESSQUEUEING] SECTION OPTIONS

2012       The [StochasticFairnessQueueing] section manages the queueing
2013       discipline (qdisc) of stochastic fairness queueing (sfq).
2014
2015       Parent=
2016           Configures the parent Queueing Discipline (qdisc). Takes one of
2017           "root", "clsact", "ingress" or a class identifier. The class
2018           identifier is specified as the major and minor numbers in
2019           hexadecimal in the range 0x1–Oxffff separated with a colon
2020           ("major:minor"). Defaults to "root".
2021
2022       Handle=
2023           Configures the major number of unique identifier of the qdisc,
2024           known as the handle. Takes a hexadecimal number in the range
2025           0x1–0xffff. Defaults to unset.
2026
2027       PerturbPeriodSec=
2028           Specifies the interval in seconds for queue algorithm perturbation.
2029           Defaults to unset.
2030

[BFIFO] SECTION OPTIONS

2032       The [BFIFO] section manages the queueing discipline (qdisc) of Byte
2033       limited Packet First In First Out (bfifo).
2034
2035       Parent=
2036           Configures the parent Queueing Discipline (qdisc). Takes one of
2037           "root", "clsact", "ingress" or a class identifier. The class
2038           identifier is specified as the major and minor numbers in
2039           hexadecimal in the range 0x1–Oxffff separated with a colon
2040           ("major:minor"). Defaults to "root".
2041
2042       Handle=
2043           Configures the major number of unique identifier of the qdisc,
2044           known as the handle. Takes a hexadecimal number in the range
2045           0x1–0xffff. Defaults to unset.
2046
2047       LimitBytes=
2048           Specifies the hard limit on the FIFO size in bytes. The size limit
2049           (a buffer size) to prevent it from overflowing in case it is unable
2050           to dequeue packets as quickly as it receives them. When this limit
2051           is reached, incoming packets are dropped. When suffixed with K, M,
2052           or G, the specified size is parsed as Kilobytes, Megabytes, or
2053           Gigabytes, respectively, to the base of 1024. Defaults to unset and
2054           kernel's default is used.
2055

[PFIFO] SECTION OPTIONS

2057       The [PFIFO] section manages the queueing discipline (qdisc) of Packet
2058       First In First Out (pfifo).
2059
2060       Parent=
2061           Configures the parent Queueing Discipline (qdisc). Takes one of
2062           "root", "clsact", "ingress" or a class identifier. The class
2063           identifier is specified as the major and minor numbers in
2064           hexadecimal in the range 0x1–Oxffff separated with a colon
2065           ("major:minor"). Defaults to "root".
2066
2067       Handle=
2068           Configures the major number of unique identifier of the qdisc,
2069           known as the handle. Takes a hexadecimal number in the range
2070           0x1–0xffff. Defaults to unset.
2071
2072       PacketLimit=
2073           Specifies the hard limit on the FIFO size in number of packets. The
2074           size limit (a buffer size) to prevent it from overflowing in case
2075           it is unable to dequeue packets as quickly as it receives them.
2076           When this limit is reached, incoming packets are dropped. An
2077           unsigned integer in the range 0–4294967294. Defaults to unset and
2078           kernel's default is used.
2079

[PFIFOHEADDROP] SECTION OPTIONS

2081       The [PFIFOHeadDrop] section manages the queueing discipline (qdisc) of
2082       Packet First In First Out Head Drop (pfifo_head_drop).
2083
2084       Parent=
2085           Configures the parent Queueing Discipline (qdisc). Takes one of
2086           "root", "clsact", "ingress" or a class identifier. The class
2087           identifier is specified as the major and minor numbers in
2088           hexadecimal in the range 0x1–Oxffff separated with a colon
2089           ("major:minor"). Defaults to "root".
2090
2091       Handle=
2092           Configures the major number of unique identifier of the qdisc,
2093           known as the handle. Takes a hexadecimal number in the range
2094           0x1–0xffff. Defaults to unset.
2095
2096       PacketLimit=
2097           As in [PFIFO] section.
2098

[PFIFOFAST] SECTION OPTIONS

2100       The [PFIFOFast] section manages the queueing discipline (qdisc) of
2101       Packet First In First Out Fast (pfifo_fast).
2102
2103       Parent=
2104           Configures the parent Queueing Discipline (qdisc). Takes one of
2105           "root", "clsact", "ingress" or a class identifier. The class
2106           identifier is specified as the major and minor numbers in
2107           hexadecimal in the range 0x1–Oxffff separated with a colon
2108           ("major:minor"). Defaults to "root".
2109
2110       Handle=
2111           Configures the major number of unique identifier of the qdisc,
2112           known as the handle. Takes a hexadecimal number in the range
2113           0x1–0xffff. Defaults to unset.
2114

[CAKE] SECTION OPTIONS

2116       The [CAKE] section manages the queueing discipline (qdisc) of Common
2117       Applications Kept Enhanced (CAKE).
2118
2119       Parent=
2120           Configures the parent Queueing Discipline (qdisc). Takes one of
2121           "root", "clsact", "ingress" or a class identifier. The class
2122           identifier is specified as the major and minor numbers in
2123           hexadecimal in the range 0x1–Oxffff separated with a colon
2124           ("major:minor"). Defaults to "root".
2125
2126       Handle=
2127           Configures the major number of unique identifier of the qdisc,
2128           known as the handle. Takes a hexadecimal number in the range
2129           0x1–0xffff. Defaults to unset.
2130
2131       OverheadBytes=
2132           Specifies that bytes to be addeded to the size of each packet.
2133           Bytes may be negative. Takes an integer in the range from -64 to
2134           256. Defaults to unset and kernel's default is used.
2135
2136       Bandwidth=
2137           Specifies the shaper bandwidth. When suffixed with K, M, or G, the
2138           specified size is parsed as Kilobits, Megabits, or Gigabits,
2139           respectively, to the base of 1000. Defaults to unset and kernel's
2140           default is used.
2141

[CONTROLLEDDELAY] SECTION OPTIONS

2143       The [ControlledDelay] section manages the queueing discipline (qdisc)
2144       of controlled delay (CoDel).
2145
2146       Parent=
2147           Configures the parent Queueing Discipline (qdisc). Takes one of
2148           "root", "clsact", "ingress" or a class identifier. The class
2149           identifier is specified as the major and minor numbers in
2150           hexadecimal in the range 0x1–Oxffff separated with a colon
2151           ("major:minor"). Defaults to "root".
2152
2153       Handle=
2154           Configures the major number of unique identifier of the qdisc,
2155           known as the handle. Takes a hexadecimal number in the range
2156           0x1–0xffff. Defaults to unset.
2157
2158       PacketLimit=
2159           Specifies the hard limit on the queue size in number of packets.
2160           When this limit is reached, incoming packets are dropped. An
2161           unsigned integer in the range 0–4294967294. Defaults to unset and
2162           kernel's default is used.
2163
2164       TargetSec=
2165           Takes a timespan. Specifies the acceptable minimum
2166           standing/persistent queue delay. Defaults to unset and kernel's
2167           default is used.
2168
2169       IntervalSec=
2170           Takes a timespan. This is used to ensure that the measured minimum
2171           delay does not become too stale. Defaults to unset and kernel's
2172           default is used.
2173
2174       ECN=
2175           Takes a boolean. This can be used to mark packets instead of
2176           dropping them. Defaults to unset and kernel's default is used.
2177
2178       CEThresholdSec=
2179           Takes a timespan. This sets a threshold above which all packets are
2180           marked with ECN Congestion Experienced (CE). Defaults to unset and
2181           kernel's default is used.
2182

[DEFICITROUNDROBINSCHEDULER] SECTION OPTIONS

2184       The [DeficitRoundRobinScheduler] section manages the queueing
2185       discipline (qdisc) of Deficit Round Robin Scheduler (DRR).
2186
2187       Parent=
2188           Configures the parent Queueing Discipline (qdisc). Takes one of
2189           "root", "clsact", "ingress" or a class identifier. The class
2190           identifier is specified as the major and minor numbers in
2191           hexadecimal in the range 0x1–Oxffff separated with a colon
2192           ("major:minor"). Defaults to "root".
2193
2194       Handle=
2195           Configures the major number of unique identifier of the qdisc,
2196           known as the handle. Takes a hexadecimal number in the range
2197           0x1–0xffff. Defaults to unset.
2198

[DEFICITROUNDROBINSCHEDULERCLASS] SECTION OPTIONS

2200       The [DeficitRoundRobinSchedulerClass] section manages the traffic
2201       control class of Deficit Round Robin Scheduler (DRR).
2202
2203       Parent=
2204           Configures the parent Queueing Discipline (qdisc). Takes one of
2205           "root", or a qdisc identifier. The qdisc identifier is specified as
2206           the major and minor numbers in hexadecimal in the range 0x1–Oxffff
2207           separated with a colon ("major:minor"). Defaults to "root".
2208
2209       ClassId=
2210           Configues the unique identifier of the class. It is specified as
2211           the major and minor numbers in hexadecimal in the range 0x1–Oxffff
2212           separated with a colon ("major:minor"). Defaults to unset.
2213
2214       QuantumBytes=
2215           Specifies the amount of bytes a flow is allowed to dequeue before
2216           the scheduler moves to the next class. When suffixed with K, M, or
2217           G, the specified size is parsed as Kilobytes, Megabytes, or
2218           Gigabytes, respectively, to the base of 1024. Defaults to the MTU
2219           of the interface.
2220

[ENHANCEDTRANSMISSIONSELECTION] SECTION OPTIONS

2222       The [EnhancedTransmissionSelection] section manages the queueing
2223       discipline (qdisc) of Enhanced Transmission Selection (ETS).
2224
2225       Parent=
2226           Configures the parent Queueing Discipline (qdisc). Takes one of
2227           "root", "clsact", "ingress" or a class identifier. The class
2228           identifier is specified as the major and minor numbers in
2229           hexadecimal in the range 0x1–Oxffff separated with a colon
2230           ("major:minor"). Defaults to "root".
2231
2232       Handle=
2233           Configures the major number of unique identifier of the qdisc,
2234           known as the handle. Takes a hexadecimal number in the range
2235           0x1–0xffff. Defaults to unset.
2236
2237       Bands=
2238           Specifies the number of bands. An unsigned integer in the range
2239           1–16. This value has to be at least large enough to cover the
2240           strict bands specified through the StrictBands= and
2241           bandwidth-sharing bands specified in QuantumBytes=.
2242
2243       StrictBands=
2244           Specifies the number of bands that should be created in strict
2245           mode. An unsigned integer in the range 1–16.
2246
2247       QuantumBytes=
2248           Specifies the white-space separated list of quantum used in
2249           band-sharing bands. When suffixed with K, M, or G, the specified
2250           size is parsed as Kilobytes, Megabytes, or Gigabytes, respectively,
2251           to the base of 1024. This setting can be specified multiple times.
2252           If an empty string is assigned, then the all previous assignments
2253           are cleared.
2254
2255       PriorityMap=
2256           The priority map maps the priority of a packet to a band. The
2257           argument is a white-space separated list of numbers. The first
2258           number indicates which band the packets with priority 0 should be
2259           put to, the second is for priority 1, and so on. There can be up to
2260           16 numbers in the list. If there are fewer, the default band that
2261           traffic with one of the unmentioned priorities goes to is the last
2262           one. Each band number must be 0..255. This setting can be specified
2263           multiple times. If an empty string is assigned, then the all
2264           previous assignments are cleared.
2265

[GENERICRANDOMEARLYDETECTION] SECTION OPTIONS

2267       The [GenericRandomEarlyDetection] section manages the queueing
2268       discipline (qdisc) of Generic Random Early Detection (GRED).
2269
2270       Parent=
2271           Configures the parent Queueing Discipline (qdisc). Takes one of
2272           "root", "clsact", "ingress" or a class identifier. The class
2273           identifier is specified as the major and minor numbers in
2274           hexadecimal in the range 0x1–Oxffff separated with a colon
2275           ("major:minor"). Defaults to "root".
2276
2277       Handle=
2278           Configures the major number of unique identifier of the qdisc,
2279           known as the handle. Takes a hexadecimal number in the range
2280           0x1–0xffff. Defaults to unset.
2281
2282       VirtualQueues=
2283           Specifies the number of virtual queues. Takes a integer in the
2284           range 1-16. Defaults to unset and kernel's default is used.
2285
2286       DefaultVirtualQueue=
2287           Specifies the number of default virtual queue. This must be less
2288           than VirtualQueue=. Defaults to unset and kernel's default is used.
2289
2290       GenericRIO=
2291           Takes a boolean. It turns on the RIO-like buffering scheme.
2292           Defaults to unset and kernel's default is used.
2293

[FAIRQUEUEINGCONTROLLEDDELAY] SECTION OPTIONS

2295       The [FairQueueingControlledDelay] section manages the queueing
2296       discipline (qdisc) of fair queuing controlled delay (FQ-CoDel).
2297
2298       Parent=
2299           Configures the parent Queueing Discipline (qdisc). Takes one of
2300           "root", "clsact", "ingress" or a class identifier. The class
2301           identifier is specified as the major and minor numbers in
2302           hexadecimal in the range 0x1–Oxffff separated with a colon
2303           ("major:minor"). Defaults to "root".
2304
2305       Handle=
2306           Configures the major number of unique identifier of the qdisc,
2307           known as the handle. Takes a hexadecimal number in the range
2308           0x1–0xffff. Defaults to unset.
2309
2310       PacketLimit=
2311           Specifies the hard limit on the real queue size. When this limit is
2312           reached, incoming packets are dropped. Defaults to unset and
2313           kernel's default is used.
2314
2315       MemoryLimitBytes=
2316           Specifies the limit on the total number of bytes that can be queued
2317           in this FQ-CoDel instance. When suffixed with K, M, or G, the
2318           specified size is parsed as Kilobytes, Megabytes, or Gigabytes,
2319           respectively, to the base of 1024. Defaults to unset and kernel's
2320           default is used.
2321
2322       Flows=
2323           Specifies the number of flows into which the incoming packets are
2324           classified. Defaults to unset and kernel's default is used.
2325
2326       TargetSec=
2327           Takes a timespan. Specifies the acceptable minimum
2328           standing/persistent queue delay. Defaults to unset and kernel's
2329           default is used.
2330
2331       IntervalSec=
2332           Takes a timespan. This is used to ensure that the measured minimum
2333           delay does not become too stale. Defaults to unset and kernel's
2334           default is used.
2335
2336       QuantumBytes=
2337           Specifies the number of bytes used as the "deficit" in the fair
2338           queuing algorithm timespan. When suffixed with K, M, or G, the
2339           specified size is parsed as Kilobytes, Megabytes, or Gigabytes,
2340           respectively, to the base of 1024. Defaults to unset and kernel's
2341           default is used.
2342
2343       ECN=
2344           Takes a boolean. This can be used to mark packets instead of
2345           dropping them. Defaults to unset and kernel's default is used.
2346
2347       CEThresholdSec=
2348           Takes a timespan. This sets a threshold above which all packets are
2349           marked with ECN Congestion Experienced (CE). Defaults to unset and
2350           kernel's default is used.
2351

[FAIRQUEUEING] SECTION OPTIONS

2353       The [FairQueueing] section manages the queueing discipline (qdisc) of
2354       fair queue traffic policing (FQ).
2355
2356       Parent=
2357           Configures the parent Queueing Discipline (qdisc). Takes one of
2358           "root", "clsact", "ingress" or a class identifier. The class
2359           identifier is specified as the major and minor numbers in
2360           hexadecimal in the range 0x1–Oxffff separated with a colon
2361           ("major:minor"). Defaults to "root".
2362
2363       Handle=
2364           Configures the major number of unique identifier of the qdisc,
2365           known as the handle. Takes a hexadecimal number in the range
2366           0x1–0xffff. Defaults to unset.
2367
2368       PacketLimit=
2369           Specifies the hard limit on the real queue size. When this limit is
2370           reached, incoming packets are dropped. Defaults to unset and
2371           kernel's default is used.
2372
2373       FlowLimit=
2374           Specifies the hard limit on the maximum number of packets queued
2375           per flow. Defaults to unset and kernel's default is used.
2376
2377       QuantumBytes=
2378           Specifies the credit per dequeue RR round, i.e. the amount of bytes
2379           a flow is allowed to dequeue at once. When suffixed with K, M, or
2380           G, the specified size is parsed as Kilobytes, Megabytes, or
2381           Gigabytes, respectively, to the base of 1024. Defaults to unset and
2382           kernel's default is used.
2383
2384       InitialQuantumBytes=
2385           Specifies the initial sending rate credit, i.e. the amount of bytes
2386           a new flow is allowed to dequeue initially. When suffixed with K,
2387           M, or G, the specified size is parsed as Kilobytes, Megabytes, or
2388           Gigabytes, respectively, to the base of 1024. Defaults to unset and
2389           kernel's default is used.
2390
2391       MaximumRate=
2392           Specifies the maximum sending rate of a flow. When suffixed with K,
2393           M, or G, the specified size is parsed as Kilobits, Megabits, or
2394           Gigabits, respectively, to the base of 1000. Defaults to unset and
2395           kernel's default is used.
2396
2397       Buckets=
2398           Specifies the size of the hash table used for flow lookups.
2399           Defaults to unset and kernel's default is used.
2400
2401       OrphanMask=
2402           Takes an unsigned integer. For packets not owned by a socket, fq is
2403           able to mask a part of hash and reduce number of buckets associated
2404           with the traffic. Defaults to unset and kernel's default is used.
2405
2406       Pacing=
2407           Takes a boolean, and enables or disables flow pacing. Defaults to
2408           unset and kernel's default is used.
2409
2410       CEThresholdSec=
2411           Takes a timespan. This sets a threshold above which all packets are
2412           marked with ECN Congestion Experienced (CE). Defaults to unset and
2413           kernel's default is used.
2414

[TRIVIALLINKEQUALIZER] SECTION OPTIONS

2416       The [TrivialLinkEqualizer] section manages the queueing discipline
2417       (qdisc) of trivial link equalizer (teql).
2418
2419       Parent=
2420           Configures the parent Queueing Discipline (qdisc). Takes one of
2421           "root", "clsact", "ingress" or a class identifier. The class
2422           identifier is specified as the major and minor numbers in
2423           hexadecimal in the range 0x1–Oxffff separated with a colon
2424           ("major:minor"). Defaults to "root".
2425
2426       Handle=
2427           Configures the major number of unique identifier of the qdisc,
2428           known as the handle. Takes a hexadecimal number in the range
2429           0x1–0xffff. Defaults to unset.
2430
2431       Id=
2432           Specifies the interface ID "N" of teql. Defaults to "0". Note that
2433           when teql is used, currently, the module sch_teql with
2434           max_equalizers=N+1 option must be loaded before systemd-networkd is
2435           started.
2436

[HIERARCHYTOKENBUCKET] SECTION OPTIONS

2438       The [HierarchyTokenBucket] section manages the queueing discipline
2439       (qdisc) of hierarchy token bucket (htb).
2440
2441       Parent=
2442           Configures the parent Queueing Discipline (qdisc). Takes one of
2443           "root", "clsact", "ingress" or a class identifier. The class
2444           identifier is specified as the major and minor numbers in
2445           hexadecimal in the range 0x1–Oxffff separated with a colon
2446           ("major:minor"). Defaults to "root".
2447
2448       Handle=
2449           Configures the major number of unique identifier of the qdisc,
2450           known as the handle. Takes a hexadecimal number in the range
2451           0x1–0xffff. Defaults to unset.
2452
2453       DefaultClass=
2454           Takes the minor id in hexadecimal of the default class.
2455           Unclassified traffic gets sent to the class. Defaults to unset.
2456
2457       RateToQuantum=
2458           Takes an unsigned integer. The DRR quantums are calculated by
2459           dividing the value configured in Rate= by RateToQuantum=.
2460

[HIERARCHYTOKENBUCKETCLASS] SECTION OPTIONS

2462       The [HierarchyTokenBucketClass] section manages the traffic control
2463       class of hierarchy token bucket (htb).
2464
2465       Parent=
2466           Configures the parent Queueing Discipline (qdisc). Takes one of
2467           "root", or a qdisc identifier. The qdisc identifier is specified as
2468           the major and minor numbers in hexadecimal in the range 0x1–Oxffff
2469           separated with a colon ("major:minor"). Defaults to "root".
2470
2471       ClassId=
2472           Configues the unique identifier of the class. It is specified as
2473           the major and minor numbers in hexadecimal in the range 0x1–Oxffff
2474           separated with a colon ("major:minor"). Defaults to unset.
2475
2476       Priority=
2477           Specifies the priority of the class. In the round-robin process,
2478           classes with the lowest priority field are tried for packets first.
2479
2480       QuantumBytes=
2481           Specifies how many bytes to serve from leaf at once. When suffixed
2482           with K, M, or G, the specified size is parsed as Kilobytes,
2483           Megabytes, or Gigabytes, respectively, to the base of 1024.
2484
2485       MTUBytes=
2486           Specifies the maximum packet size we create. When suffixed with K,
2487           M, or G, the specified size is parsed as Kilobytes, Megabytes, or
2488           Gigabytes, respectively, to the base of 1024.
2489
2490       OverheadBytes=
2491           Takes an unsigned integer which specifies per-packet size overhead
2492           used in rate computations. When suffixed with K, M, or G, the
2493           specified size is parsed as Kilobytes, Megabytes, or Gigabytes,
2494           respectively, to the base of 1024.
2495
2496       Rate=
2497           Specifies the maximum rate this class and all its children are
2498           guaranteed. When suffixed with K, M, or G, the specified size is
2499           parsed as Kilobits, Megabits, or Gigabits, respectively, to the
2500           base of 1000. This setting is mandatory.
2501
2502       CeilRate=
2503           Specifies the maximum rate at which a class can send, if its parent
2504           has bandwidth to spare. When suffixed with K, M, or G, the
2505           specified size is parsed as Kilobits, Megabits, or Gigabits,
2506           respectively, to the base of 1000. When unset, the value specified
2507           with Rate= is used.
2508
2509       BufferBytes=
2510           Specifies the maximum bytes burst which can be accumulated during
2511           idle period. When suffixed with K, M, or G, the specified size is
2512           parsed as Kilobytes, Megabytes, or Gigabytes, respectively, to the
2513           base of 1024.
2514
2515       CeilBufferBytes=
2516           Specifies the maximum bytes burst for ceil which can be accumulated
2517           during idle period. When suffixed with K, M, or G, the specified
2518           size is parsed as Kilobytes, Megabytes, or Gigabytes, respectively,
2519           to the base of 1024.
2520

[HEAVYHITTERFILTER] SECTION OPTIONS

2522       The [HeavyHitterFilter] section manages the queueing discipline (qdisc)
2523       of Heavy Hitter Filter (hhf).
2524
2525       Parent=
2526           Configures the parent Queueing Discipline (qdisc). Takes one of
2527           "root", "clsact", "ingress" or a class identifier. The class
2528           identifier is specified as the major and minor numbers in
2529           hexadecimal in the range 0x1–Oxffff separated with a colon
2530           ("major:minor"). Defaults to "root".
2531
2532       Handle=
2533           Configures the major number of unique identifier of the qdisc,
2534           known as the handle. Takes a hexadecimal number in the range
2535           0x1–0xffff. Defaults to unset.
2536
2537       PacketLimit=
2538           Specifies the hard limit on the queue size in number of packets.
2539           When this limit is reached, incoming packets are dropped. An
2540           unsigned integer in the range 0–4294967294. Defaults to unset and
2541           kernel's default is used.
2542

[QUICKFAIRQUEUEING] SECTION OPTIONS

2544       The [QuickFairQueueing] section manages the queueing discipline (qdisc)
2545       of Quick Fair Queueing (QFQ).
2546
2547       Parent=
2548           Configures the parent Queueing Discipline (qdisc). Takes one of
2549           "root", "clsact", "ingress" or a class identifier. The class
2550           identifier is specified as the major and minor numbers in
2551           hexadecimal in the range 0x1–Oxffff separated with a colon
2552           ("major:minor"). Defaults to "root".
2553
2554       Handle=
2555           Configures the major number of unique identifier of the qdisc,
2556           known as the handle. Takes a hexadecimal number in the range
2557           0x1–0xffff. Defaults to unset.
2558

[QUICKFAIRQUEUEINGCLASS] SECTION OPTIONS

2560       The [QuickFairQueueingClass] section manages the traffic control class
2561       of Quick Fair Queueing (qfq).
2562
2563       Parent=
2564           Configures the parent Queueing Discipline (qdisc). Takes one of
2565           "root", or a qdisc identifier. The qdisc identifier is specified as
2566           the major and minor numbers in hexadecimal in the range 0x1–Oxffff
2567           separated with a colon ("major:minor"). Defaults to "root".
2568
2569       ClassId=
2570           Configues the unique identifier of the class. It is specified as
2571           the major and minor numbers in hexadecimal in the range 0x1–Oxffff
2572           separated with a colon ("major:minor"). Defaults to unset.
2573
2574       Weight=
2575           Specifies the weight of the class. Takes an integer in the range
2576           1..1023. Defaults to unset in which case the kernel default is
2577           used.
2578
2579       MaxPacketBytes=
2580           Specifies the maximum packet size in bytes for the class. When
2581           suffixed with K, M, or G, the specified size is parsed as
2582           Kilobytes, Megabytes, or Gigabytes, respectively, to the base of
2583           1024. When unset, the kernel default is used.
2584

[BRIDGEVLAN] SECTION OPTIONS

2586       The [BridgeVLAN] section manages the VLAN ID configuration of a bridge
2587       port and accepts the following keys. Specify several [BridgeVLAN]
2588       sections to configure several VLAN entries. The VLANFiltering= option
2589       has to be enabled, see the [Bridge] section in systemd.netdev(5).
2590
2591       VLAN=
2592           The VLAN ID allowed on the port. This can be either a single ID or
2593           a range M-N. VLAN IDs are valid from 1 to 4094.
2594
2595       EgressUntagged=
2596           The VLAN ID specified here will be used to untag frames on egress.
2597           Configuring EgressUntagged= implicates the use of VLAN= above and
2598           will enable the VLAN ID for ingress as well. This can be either a
2599           single ID or a range M-N.
2600
2601       PVID=
2602           The Port VLAN ID specified here is assigned to all untagged frames
2603           at ingress.  PVID= can be used only once. Configuring PVID=
2604           implicates the use of VLAN= above and will enable the VLAN ID for
2605           ingress as well.
2606

EXAMPLES

2608       Example 1. Static network configuration
2609
2610           # /etc/systemd/network/50-static.network
2611           [Match]
2612           Name=enp2s0
2613
2614           [Network]
2615           Address=192.168.0.15/24
2616           Gateway=192.168.0.1
2617
2618       This brings interface "enp2s0" up with a static address. The specified
2619       gateway will be used for a default route.
2620
2621       Example 2. DHCP on ethernet links
2622
2623           # /etc/systemd/network/80-dhcp.network
2624           [Match]
2625           Name=en*
2626
2627           [Network]
2628           DHCP=yes
2629
2630       This will enable DHCPv4 and DHCPv6 on all interfaces with names
2631       starting with "en" (i.e. ethernet interfaces).
2632
2633       Example 3. IPv6 Prefix Delegation
2634
2635           # /etc/systemd/network/55-ipv6-pd-upstream.network
2636           [Match]
2637           Name=enp1s0
2638
2639           [Network]
2640           DHCP=ipv6
2641
2642           # /etc/systemd/network/56-ipv6-pd-downstream.network
2643           [Match]
2644           Name=enp2s0
2645
2646           [Network]
2647           IPv6PrefixDelegation=dhcpv6
2648
2649       This will enable IPv6 PD on the interface enp1s0 as an upstream
2650       interface where the DHCPv6 client is running and enp2s0 as a downstream
2651       interface where the prefix is delegated to.
2652
2653       Example 4. A bridge with two enslaved links
2654
2655           # /etc/systemd/network/25-bridge-static.network
2656           [Match]
2657           Name=bridge0
2658
2659           [Network]
2660           Address=192.168.0.15/24
2661           Gateway=192.168.0.1
2662           DNS=192.168.0.1
2663
2664           # /etc/systemd/network/25-bridge-slave-interface-1.network
2665           [Match]
2666           Name=enp2s0
2667
2668           [Network]
2669           Bridge=bridge0
2670
2671           # /etc/systemd/network/25-bridge-slave-interface-2.network
2672           [Match]
2673           Name=wlp3s0
2674
2675           [Network]
2676           Bridge=bridge0
2677
2678       This creates a bridge and attaches devices "enp2s0" and "wlp3s0" to it.
2679       The bridge will have the specified static address and network assigned,
2680       and a default route via the specified gateway will be added. The
2681       specified DNS server will be added to the global list of DNS resolvers.
2682
2683       Example 5.
2684
2685           # /etc/systemd/network/20-bridge-slave-interface-vlan.network
2686           [Match]
2687           Name=enp2s0
2688
2689           [Network]
2690           Bridge=bridge0
2691
2692           [BridgeVLAN]
2693           VLAN=1-32
2694           PVID=42
2695           EgressUntagged=42
2696
2697           [BridgeVLAN]
2698           VLAN=100-200
2699
2700           [BridgeVLAN]
2701           EgressUntagged=300-400
2702
2703       This overrides the configuration specified in the previous example for
2704       the interface "enp2s0", and enables VLAN on that bridge port. VLAN IDs
2705       1-32, 42, 100-400 will be allowed. Packets tagged with VLAN IDs 42,
2706       300-400 will be untagged when they leave on this interface. Untagged
2707       packets which arrive on this interface will be assigned VLAN ID 42.
2708
2709       Example 6. Various tunnels
2710
2711           /etc/systemd/network/25-tunnels.network
2712           [Match]
2713           Name=ens1
2714
2715           [Network]
2716           Tunnel=ipip-tun
2717           Tunnel=sit-tun
2718           Tunnel=gre-tun
2719           Tunnel=vti-tun
2720
2721
2722           /etc/systemd/network/25-tunnel-ipip.netdev
2723           [NetDev]
2724           Name=ipip-tun
2725           Kind=ipip
2726
2727
2728           /etc/systemd/network/25-tunnel-sit.netdev
2729           [NetDev]
2730           Name=sit-tun
2731           Kind=sit
2732
2733
2734           /etc/systemd/network/25-tunnel-gre.netdev
2735           [NetDev]
2736           Name=gre-tun
2737           Kind=gre
2738
2739
2740           /etc/systemd/network/25-tunnel-vti.netdev
2741           [NetDev]
2742           Name=vti-tun
2743           Kind=vti
2744
2745
2746       This will bring interface "ens1" up and create an IPIP tunnel, a SIT
2747       tunnel, a GRE tunnel, and a VTI tunnel using it.
2748
2749       Example 7. A bond device
2750
2751           # /etc/systemd/network/30-bond1.network
2752           [Match]
2753           Name=bond1
2754
2755           [Network]
2756           DHCP=ipv6
2757
2758           # /etc/systemd/network/30-bond1.netdev
2759           [NetDev]
2760           Name=bond1
2761           Kind=bond
2762
2763           # /etc/systemd/network/30-bond1-dev1.network
2764           [Match]
2765           MACAddress=52:54:00:e9:64:41
2766
2767           [Network]
2768           Bond=bond1
2769
2770           # /etc/systemd/network/30-bond1-dev2.network
2771           [Match]
2772           MACAddress=52:54:00:e9:64:42
2773
2774           [Network]
2775           Bond=bond1
2776
2777       This will create a bond device "bond1" and enslave the two devices with
2778       MAC addresses 52:54:00:e9:64:41 and 52:54:00:e9:64:42 to it. IPv6 DHCP
2779       will be used to acquire an address.
2780
2781       Example 8. Virtual Routing and Forwarding (VRF)
2782
2783       Add the "bond1" interface to the VRF master interface "vrf1". This will
2784       redirect routes generated on this interface to be within the routing
2785       table defined during VRF creation. For kernels before 4.8 traffic won't
2786       be redirected towards the VRFs routing table unless specific ip-rules
2787       are added.
2788
2789           # /etc/systemd/network/25-vrf.network
2790           [Match]
2791           Name=bond1
2792
2793           [Network]
2794           VRF=vrf1
2795
2796       Example 9. MacVTap
2797
2798       This brings up a network interface "macvtap-test" and attaches it to
2799       "enp0s25".
2800
2801           # /usr/lib/systemd/network/25-macvtap.network
2802           [Match]
2803           Name=enp0s25
2804
2805           [Network]
2806           MACVTAP=macvtap-test
2807
2808       Example 10. A Xfrm interface with physical underlying device.
2809
2810           # /etc/systemd/network/27-xfrm.netdev
2811           [NetDev]
2812           Name=xfrm0
2813
2814           [Xfrm]
2815           InterfaceId=7
2816
2817           # /etc/systemd/network/27-eth0.network
2818           [Match]
2819           Name=eth0
2820
2821           [Network]
2822           Xfrm=xfrm0
2823
2824       This creates a "xfrm0" interface and binds it to the "eth0" device.
2825       This allows hardware based ipsec offloading to the "eth0" nic. If
2826       offloading is not needed, xfrm interfaces can be assigned to the "lo"
2827       device.
2828

SEE ALSO

2830       systemd(1), systemd-networkd.service(8), systemd.link(5),
2831       systemd.netdev(5), systemd-resolved.service(8)
2832

NOTES

2834        1. RFC 7217
2835           https://tools.ietf.org/html/rfc7217
2836
2837        2. Link-Local Multicast Name Resolution
2838           https://tools.ietf.org/html/rfc4795
2839
2840        3. Multicast DNS
2841           https://tools.ietf.org/html/rfc6762
2842
2843        4. DNS-over-TLS
2844           https://tools.ietf.org/html/rfc7858
2845
2846        5. DNSSEC
2847           https://tools.ietf.org/html/rfc4033
2848
2849        6. IEEE 802.1AB-2016
2850           https://standards.ieee.org/findstds/standard/802.1AB-2016.html
2851
2852        7. ip-sysctl.txt
2853           https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt
2854
2855        8. RFC 4941
2856           https://tools.ietf.org/html/rfc4941
2857
2858        9. RFC 1027
2859           https://tools.ietf.org/html/rfc1027
2860
2861       10. RFC 6275
2862           https://tools.ietf.org/html/rfc6275
2863
2864       11. RFC 5224
2865           https://tools.ietf.org/html/rfc5227
2866
2867       12. RFC 4862
2868           https://tools.ietf.org/html/rfc4862
2869
2870       13. RFC 3041
2871           https://tools.ietf.org/html/rfc3041
2872
2873       14. RFC 3484
2874           https://tools.ietf.org/html/rfc3484
2875
2876       15. RFC 4191
2877           https://tools.ietf.org/html/rfc4191
2878
2879       16. RFC 7844
2880           https://tools.ietf.org/html/rfc7844
2881
2882       17. RFC 8520
2883           https://tools.ietf.org/html/rfc8520
2884
2885       18. C-style escapes
2886           https://en.wikipedia.org/wiki/Escape_sequences_in_C#Table_of_escape_sequences
2887
2888       19. RFC 3315
2889           https://tools.ietf.org/html/rfc3315#section-17.2.1
2890
2891       20. RFC 7084
2892           https://tools.ietf.org/html/rfc7084
2893
2894       21. RFC 4291
2895           https://tools.ietf.org/html/rfc4291#section-2.5.4
2896
2897       22. RFC 4861
2898           https://tools.ietf.org/html/rfc4861
2899
2900
2901
2902systemd 246                                                 SYSTEMD.NETWORK(5)
Impressum