Provided by: systemd_237-3ubuntu10.57_amd64 
NAME
systemd.network - Network configuration
SYNOPSIS
network.network
DESCRIPTION
Network setup is performed by systemd-networkd(8).
The main network file must have the extension .network; other extensions are ignored. Networks are
applied to links whenever the links appear.
The .network files are read from the files located in the system network directory /lib/systemd/network,
the volatile runtime network directory /run/systemd/network and the local administration network
directory /etc/systemd/network. All configuration files are collectively sorted and processed in lexical
order, regardless of the directories in which they live. However, files with identical filenames replace
each other. Files in /etc have the highest priority, files in /run take precedence over files with the
same name in /lib. This can be used to override a system-supplied configuration file with a local file if
needed. As a special case, an empty file (file size 0) or symlink with the same name pointing to
/dev/null disables the configuration file entirely (it is "masked").
Along with the network file foo.network, a "drop-in" directory foo.network.d/ may exist. All files with
the suffix ".conf" from this directory will be parsed after the file itself is parsed. This is useful to
alter or add configuration settings, without having to modify the main configuration file. Each drop-in
file must have appropriate section headers.
In addition to /etc/systemd/network, drop-in ".d" directories can be placed in /lib/systemd/network or
/run/systemd/network directories. Drop-in files in /etc take precedence over those in /run which in turn
take precedence over those in /lib. Drop-in files under any of these directories take precedence over the
main netdev file wherever located. (Of course, since /run is temporary and /usr/lib is for vendors, it is
unlikely drop-ins should be used in either of those places.)
Note that an interface without any static IPv6 addresses configured, and neither DHCPv6 nor IPv6LL
enabled, shall be considered to have no IPv6 support. IPv6 will be automatically disabled for that
interface by writing "1" to /proc/sys/net/ipv6/conf/ifname/disable_ipv6.
[MATCH] SECTION OPTIONS
The network file contains a "[Match]" section, which determines if a given network file may be applied to
a given device; and a "[Network]" section specifying how the device should be configured. The first (in
lexical order) of the network files that matches a given device is applied, all later files are ignored,
even if they match as well.
A network file is said to match a device if each of the entries in the "[Match]" section matches, or if
the section is empty. The following keys are accepted:
MACAddress=
The hardware address of the interface (use full colon-delimited hexadecimal, e.g.,
01:23:45:67:89:ab).
Path=
A whitespace-separated list of shell-style globs matching the persistent path, as exposed by the udev
property "ID_PATH". If the list is prefixed with a "!", the test is inverted; i.e. it is true when
"ID_PATH" does not match any item in the list.
Driver=
A whitespace-separated list of shell-style globs matching the driver currently bound to the device,
as exposed by the udev property "DRIVER" of its parent device, or if that is not set the driver as
exposed by "ethtool -i" of the device itself. If the list is prefixed with a "!", the test is
inverted.
Type=
A whitespace-separated list of shell-style globs matching the device type, as exposed by the udev
property "DEVTYPE". If the list is prefixed with a "!", the test is inverted.
Name=
A whitespace-separated list of shell-style globs matching the device name, as exposed by the udev
property "INTERFACE". If the list is prefixed with a "!", the test is inverted.
Host=
Matches against the hostname or machine ID of the host. See "ConditionHost=" in systemd.unit(5) for
details.
Virtualization=
Checks whether the system is executed in a virtualized environment and optionally test whether it is
a specific implementation. See "ConditionVirtualization=" in systemd.unit(5) for details.
KernelCommandLine=
Checks whether a specific kernel command line option is set (or if prefixed with the exclamation mark
unset). See "ConditionKernelCommandLine=" in systemd.unit(5) for details.
KernelVersion=
Checks whether the kernel version (as reported by uname -r) matches a certain expression (or if
prefixed with the exclamation mark does not match it). See "ConditionKernelVersion=" in
systemd.unit(5) for details.
Architecture=
Checks whether the system is running on a specific architecture. See "ConditionArchitecture=" in
systemd.unit(5) for details.
KeepConfiguration=
Takes a boolean or one of "static", "dhcp-on-stop", "dhcp". When "static", systemd-networkd will not
drop static addresses and routes on starting up process. When set to "dhcp-on-stop", systemd-networkd
will not drop addresses and routes on stopping the daemon. When "dhcp", the addresses and routes
provided by a DHCP server will never be dropped even if the DHCP lease expires. This is contrary to
the DHCP specification, but may be the best choice if, e.g., the root filesystem relies on this
connection. The setting "dhcp" implies "dhcp-on-stop", and "yes" implies "dhcp" and "static".
Defaults to "dhcp-on-stop".
[LINK] SECTION OPTIONS
The "[Link]" section accepts the following keys:
MACAddress=
The hardware address to set for the device.
MTUBytes=
The maximum transmission unit in bytes to set for the device. The usual suffixes K, M, G, are
supported and are understood to the base of 1024.
Note that if IPv6 is enabled on the interface, and the MTU is chosen below 1280 (the minimum MTU for
IPv6) it will automatically be increased to this value.
ARP=
A boolean. Enables or disables the ARP (low-level Address Resolution Protocol) for this interface.
Defaults to unset, which means that the kernel default will be used.
For example, disabling ARP is useful when creating multiple MACVLAN or VLAN virtual interfaces atop a
single lower-level physical interface, which will then only serve as a link/"bridge" device
aggregating traffic to the same physical link and not participate in the network otherwise.
Unmanaged=
A boolean. When "yes", no attempts are made to bring up or configure matching links, equivalent to
when there are no matching network files. Defaults to "no".
This is useful for preventing later matching network files from interfering with certain interfaces
that are fully controlled by other applications.
RequiredForOnline=
A boolean. When "yes", the network is deemed required when determining whether the system is online
when running "systemd-networkd-wait-online". When "no", the network is ignored when checking for
online state. Defaults to "yes".
The network will be brought up normally in all cases, but in the event that there is no address being
assigned by DHCP or the cable is not plugged in, the link will simply remain offline and be skipped
automatically by "systemd-networkd-wait-online" if "RequiredForOnline=true".
[NETWORK] SECTION OPTIONS
The "[Network]" section accepts the following keys:
Description=
A description of the device. This is only used for presentation purposes.
DHCP=
Enables DHCPv4 and/or DHCPv6 client support. Accepts "yes", "no", "ipv4", or "ipv6". Defaults to
"no".
Note that DHCPv6 will by default be triggered by Router Advertisement, if that is enabled, regardless
of this parameter. By enabling DHCPv6 support explicitly, the DHCPv6 client will be started
regardless of the presence of routers on the link, or what flags the routers pass. See
"IPv6AcceptRA=".
Furthermore, note that by default the domain name specified through DHCP, on Ubuntu, are used for
name resolution. See option UseDomains= below.
See the "[DHCP]" section below for further configuration options for the DHCP client support.
DHCPServer=
A boolean. Enables DHCPv4 server support. Defaults to "no". Further settings for the DHCP server may
be set in the "[DHCPServer]" section described below.
LinkLocalAddressing=
Enables link-local address autoconfiguration. Accepts "yes", "no", "ipv4", or "ipv6". Defaults to
"ipv6".
IPv4LLRoute=
A boolean. When true, sets up the route needed for non-IPv4LL hosts to communicate with IPv4LL-only
hosts. Defaults to false.
IPv6Token=
An IPv6 address with the top 64 bits unset. When set, indicates the 64-bit interface part of SLAAC
IPv6 addresses for this link. Note that the token is only ever used for SLAAC, and not for DHCPv6
addresses, even in the case DHCP is requested by router advertisement. By default, the token is
autogenerated.
LLMNR=
A boolean or "resolve". When true, enables Link-Local Multicast Name Resolution[1] on the link. When
set to "resolve", only resolution is enabled, but not host registration and announcement. Defaults to
true. This setting is read by systemd-resolved.service(8).
MulticastDNS=
A boolean or "resolve". When true, enables Multicast DNS[2] support on the link. When set to
"resolve", only resolution is enabled, but not host or service registration and announcement.
Defaults to false. This setting is read by systemd-resolved.service(8).
DNSSEC=
A boolean or "allow-downgrade". When true, enables DNSSEC[3] DNS validation support on the link. When
set to "allow-downgrade", compatibility with non-DNSSEC capable networks is increased, by
automatically turning off DNSSEC in this case. This option defines a per-interface setting for
resolved.conf(5)'s global DNSSEC= option. Defaults to false. This setting is read by systemd-
resolved.service(8).
DNSSECNegativeTrustAnchors=
A space-separated list of DNSSEC negative trust anchor domains. If specified and DNSSEC is enabled,
look-ups done via the interface's DNS server will be subject to the list of negative trust anchors,
and not require authentication for the specified domains, or anything below it. Use this to disable
DNSSEC authentication for specific private domains, that cannot be proven valid using the Internet
DNS hierarchy. Defaults to the empty list. This setting is read by systemd-resolved.service(8).
LLDP=
Controls support for Ethernet LLDP packet reception. LLDP is a link-layer protocol commonly
implemented on professional routers and bridges which announces which physical port a system is
connected to, as well as other related data. Accepts a boolean or the special value "routers-only".
When true, incoming LLDP packets are accepted and a database of all LLDP neighbors maintained. If
"routers-only" is set only LLDP data of various types of routers is collected and LLDP data about
other types of devices ignored (such as stations, telephones and others). If false, LLDP reception is
disabled. Defaults to "routers-only". Use networkctl(1) to query the collected neighbor data. LLDP is
only available on Ethernet links. See EmitLLDP= below for enabling LLDP packet emission from the
local system.
EmitLLDP=
Controls support for Ethernet LLDP packet emission. Accepts a boolean parameter or the special values
"nearest-bridge", "non-tpmr-bridge" and "customer-bridge". Defaults to false, which turns off LLDP
packet emission. If not false, a short LLDP packet with information about the local system is sent
out in regular intervals on the link. The LLDP packet will contain information about the local host
name, the local machine ID (as stored in machine-id(5)) and the local interface name, as well as the
pretty hostname of the system (as set in machine-info(5)). LLDP emission is only available on
Ethernet links. Note that this setting passes data suitable for identification of host to the network
and should thus not be enabled on untrusted networks, where such identification data should not be
made available. Use this option to permit other systems to identify on which interfaces they are
connected to this system. The three special values control propagation of the LLDP packets. The
"nearest-bridge" setting permits propagation only to the nearest connected bridge, "non-tpmr-bridge"
permits propagation across Two-Port MAC Relays, but not any other bridges, and "customer-bridge"
permits propagation until a customer bridge is reached. For details about these concepts, see IEEE
802.1AB-2009[4]. Note that configuring this setting to true is equivalent to "nearest-bridge", the
recommended and most restricted level of propagation. See LLDP= above for an option to enable LLDP
reception.
BindCarrier=
A link name or a list of link names. When set, controls the behavior of the current link. When all
links in the list are in an operational down state, the current link is brought down. When at least
one link has carrier, the current interface is brought up.
Address=
A static IPv4 or IPv6 address and its prefix length, separated by a "/" character. Specify this key
more than once to configure several addresses. The format of the address must be as described in
inet_pton(3). This is a short-hand for an [Address] section only containing an Address key (see
below). This option may be specified more than once.
If the specified address is 0.0.0.0 (for IPv4) or [::] (for IPv6), a new address range of the
requested size is automatically allocated from a system-wide pool of unused ranges. The allocated
range is checked against all current network interfaces and all known network configuration files to
avoid address range conflicts. The default system-wide pool consists of 192.168.0.0/16, 172.16.0.0/12
and 10.0.0.0/8 for IPv4, and fc00::/7 for IPv6. This functionality is useful to manage a large number
of dynamically created network interfaces with the same network configuration and automatic address
range assignment.
Gateway=
The gateway address, which must be in the format described in inet_pton(3). This is a short-hand for
a [Route] section only containing a Gateway key. This option may be specified more than once.
DNS=
A DNS server address, which must be in the format described in inet_pton(3). This option may be
specified more than once. This setting is read by systemd-resolved.service(8).
Domains=
A list of domains which should be resolved using the DNS servers on this link. Each item in the list
should be a domain name, optionally prefixed with a tilde ("~"). The domains with the prefix are
called "routing-only domains". The domains without the prefix are called "search domains" and are
first used as search suffixes for extending single-label host names (host names containing no dots)
to become fully qualified domain names (FQDNs). If a single-label host name is resolved on this
interface, each of the specified search domains are appended to it in turn, converting it into a
fully qualified domain name, until one of them may be successfully resolved.
Both "search" and "routing-only" domains are used for routing of DNS queries: look-ups for host names
ending in those domains (hence also single label names, if any "search domains" are listed), are
routed to the DNS servers configured for this interface. The domain routing logic is particularly
useful on multi-homed hosts with DNS servers serving particular private DNS zones on each interface.
The "routing-only" domain "~." (the tilde indicating definition of a routing domain, the dot
referring to the DNS root domain which is the implied suffix of all valid DNS names) has special
effect. It causes all DNS traffic which does not match another configured domain routing entry to be
routed to DNS servers specified for this interface. This setting is useful to prefer a certain set of
DNS servers if a link on which they are connected is available.
This setting is read by systemd-resolved.service(8). "Search domains" correspond to the domain and
search entries in resolv.conf(5). Domain name routing has no equivalent in the traditional glibc API,
which has no concept of domain name servers limited to a specific link.
NTP=
An NTP server address. This option may be specified more than once. This setting is read by systemd-
timesyncd.service(8).
IPForward=
Configures IP packet forwarding for the system. If enabled, incoming packets on any network interface
will be forwarded to any other interfaces according to the routing table. Takes either a boolean
argument, or the values "ipv4" or "ipv6", which only enable IP packet forwarding for the specified
address family. This controls the net.ipv4.ip_forward and net.ipv6.conf.all.forwarding sysctl options
of the network interface (see ip-sysctl.txt[5] for details about sysctl options). Defaults to "no".
Note: this setting controls a global kernel option, and does so one way only: if a network that has
this setting enabled is set up the global setting is turned on. However, it is never turned off
again, even after all networks with this setting enabled are shut down again.
To allow IP packet forwarding only between specific network interfaces use a firewall.
IPMasquerade=
Configures IP masquerading for the network interface. If enabled, packets forwarded from the network
interface will be appear as coming from the local host. Takes a boolean argument. Implies
IPForward=ipv4. Defaults to "no".
IPv6PrivacyExtensions=
Configures use of stateless temporary addresses that change over time (see RFC 4941[6], Privacy
Extensions for Stateless Address Autoconfiguration in IPv6). Takes a boolean or the special values
"prefer-public" and "kernel". When true, enables the privacy extensions and prefers temporary
addresses over public addresses. When "prefer-public", enables the privacy extensions, but prefers
public addresses over temporary addresses. When false, the privacy extensions remain disabled. When
"kernel", the kernel's default setting will be left in place. Defaults to "no".
IPv6AcceptRA=
Enable or disable IPv6 Router Advertisement (RA) reception support for the interface. Takes a boolean
parameter. If true, RAs are accepted; if false, RAs are ignored, independently of the local
forwarding state. When not set, the kernel default is used, and RAs are accepted only when local
forwarding is disabled for that interface. When RAs are accepted, they may trigger the start of the
DHCPv6 client if the relevant flags are set in the RA data, or if no routers are found on the link.
Further settings for the IPv6 RA support may be configured in the "[IPv6AcceptRA]" section, see
below.
Also see ip-sysctl.txt[5] in the kernel documentation regarding "accept_ra", but note that systemd's
setting of 1 (i.e. true) corresponds to kernel's setting of 2.
IPv6DuplicateAddressDetection=
Configures the amount of IPv6 Duplicate Address Detection (DAD) probes to send. Defaults to unset.
IPv6HopLimit=
Configures IPv6 Hop Limit. For each router that forwards the packet, the hop limit is decremented by
1. When the hop limit field reaches zero, the packet is discarded. Defaults to unset.
IPv4ProxyARP=
A boolean. Configures proxy ARP for IPv4. Proxy ARP is the technique in which one host, usually a
router, answers ARP requests intended for another machine. By "faking" its identity, the router
accepts responsibility for routing packets to the "real" destination. (see RFC 1027[7]. Defaults to
unset.
IPv6ProxyNDP=
A boolean. Configures proxy NDP for IPv6. Proxy NDP (Neighbor Discovery Protocol) is a technique for
IPv6 to allow routing of addresses to a different destination when peers expect them to be present on
a certain physical link. In this case a router answers Neighbour Advertisement messages intended for
another machine by offering its own MAC address as destination. Unlike proxy ARP for IPv4, it is not
enabled globally, but will only send Neighbour Advertisement messages for addresses in the IPv6
neighbor proxy table, which can also be shown by ip -6 neighbour show proxy. systemd-networkd will
control the per-interface `proxy_ndp` switch for each configured interface depending on this option.
Defautls to unset.
IPv6ProxyNDPAddress=
An IPv6 address, for which Neighbour Advertisement messages will be proxied. This option may be
specified more than once. systemd-networkd will add the IPv6ProxyNDPAddress= entries to the kernel's
IPv6 neighbor proxy table. This option implies IPv6ProxyNDP=true but has no effect if IPv6ProxyNDP
has been set to false. Defaults to unset.
IPv6PrefixDelegation=
Whether to enable or disable Router Advertisement sending on a link. Allowed values are "static"
which distributes prefixes as defined in the "[IPv6PrefixDelegation]" and any "[IPv6Prefix]"
sections, "dhcpv6" which requests prefixes using a DHCPv6 client configured for another link and any
values configured in the "[IPv6PrefixDelegation]" section while ignoring all static prefix
configuration sections, "yes" which uses both static configuration and DHCPv6, and "false" which
turns off IPv6 prefix delegation altogether. Defaults to "false". See the "[IPv6PrefixDelegation]"
and the "[IPv6Prefix]" sections for more configuration options.
IPv6MTUBytes=
Configures IPv6 maximum transmission unit (MTU). An integer greater than or equal to 1280 bytes.
Defaults to unset.
Bridge=
The name of the bridge to add the link to. See systemd.netdev(5).
Bond=
The name of the bond to add the link to. See systemd.netdev(5).
VRF=
The name of the VRF to add the link to. See systemd.netdev(5).
VLAN=
The name of a VLAN to create on the link. See systemd.netdev(5). This option may be specified more
than once.
MACVLAN=
The name of a MACVLAN to create on the link. See systemd.netdev(5). This option may be specified more
than once.
VXLAN=
The name of a VXLAN to create on the link. See systemd.netdev(5). This option may be specified more
than once.
Tunnel=
The name of a Tunnel to create on the link. See systemd.netdev(5). This option may be specified more
than once.
ActiveSlave=
A boolean. Specifies the new active slave. The "ActiveSlave=" option is only valid for following
modes: "active-backup", "balance-alb" and "balance-tlb". Defaults to false.
PrimarySlave=
A boolean. Specifies which slave is the primary device. The specified device will always be the
active slave while it is available. Only when the primary is off-line will alternate devices be used.
This is useful when one slave is preferred over another, e.g. when one slave has higher throughput
than another. The "PrimarySlave=" option is only valid for following modes: "active-backup",
"balance-alb" and "balance-tlb". Defaults to false.
ConfigureWithoutCarrier=
A boolean. Allows networkd to configure a specific link even if it has no carrier. Defaults to false.
IgnoreCarrierLoss=
Takes a boolean. Allows networkd to retain both the static and dynamic configuration of the interface
even if its carrier is lost. When unset, the value specified with ConfigureWithoutCarrier= is used.
[ADDRESS] SECTION OPTIONS
An "[Address]" section accepts the following keys. Specify several "[Address]" sections to configure
several addresses.
Address=
As in the "[Network]" section. This key is mandatory.
Peer=
The peer address in a point-to-point connection. Accepts the same format as the "Address" key.
Broadcast=
The broadcast address, which must be in the format described in inet_pton(3). This key only applies
to IPv4 addresses. If it is not given, it is derived from the "Address" key.
Label=
An address label.
PreferredLifetime=
Allows the default "preferred lifetime" of the address to be overridden. Only three settings are
accepted: "forever" or "infinity" which is the default and means that the address never expires, and
"0" which means that the address is considered immediately "expired" and will not be used, unless
explicitly requested. A setting of PreferredLifetime=0 is useful for addresses which are added to be
used only by a specific application, which is then configured to use them explicitly.
Scope=
The scope of the address, which can be "global", "link" or "host" or an unsigned integer ranges 0 to
255. Defaults to "global".
HomeAddress=
Takes a boolean argument. Designates this address the "home address" as defined in RFC 6275[8].
Supported only on IPv6. Defaults to false.
DuplicateAddressDetection=
Takes a boolean argument. Do not perform Duplicate Address Detection RFC 4862[9] when adding this
address. Supported only on IPv6. Defaults to false.
ManageTemporaryAddress=
Takes a boolean argument. If true the kernel manage temporary addresses created from this one as
template on behalf of Privacy Extensions RFC 3041[10]. For this to become active, the use_tempaddr
sysctl setting has to be set to a value greater than zero. The given address needs to have a prefix
length of 64. This flag allows to use privacy extensions in a manually configured network, just like
if stateless auto-configuration was active. Defaults to false.
PrefixRoute=
Takes a boolean argument. When adding or modifying an IPv6 address, the userspace application needs a
way to suppress adding a prefix route. This is for example relevant together with
IFA_F_MANAGERTEMPADDR, where userspace creates autoconf generated addresses, but depending on
on-link, no route for the prefix should be added. Defaults to false.
AutoJoin=
Takes a boolean argument. Joining multicast group on ethernet level via ip maddr command would not
work if we have an Ethernet switch that does IGMP snooping since the switch would not replicate
multicast packets on ports that did not have IGMP reports for the multicast addresses. Linux vxlan
interfaces created via ip link add vxlan or networkd's netdev kind vxlan have the group option that
enables then to do the required join. By extending ip address command with option "autojoin" we can
get similar functionality for openvswitch (OVS) vxlan interfaces as well as other tunneling
mechanisms that need to receive multicast traffic. Defaults to "no".
[IPV6ADDRESSLABEL] SECTION OPTIONS
An "[IPv6AddressLabel]" section accepts the following keys. Specify several "[IPv6AddressLabel]" sections
to configure several address labels. IPv6 address labels are used for address selection. See RFC
3484[11]. Precedence is managed by userspace, and only the label itself is stored in the kernel
Label=
The label for the prefix (an unsigned integer) ranges 0 to 4294967294. 0xffffffff is reserved. This
key is mandatory.
Prefix=
IPv6 prefix is an address with a prefix length, separated by a slash "/" character. This key is
mandatory.
[ROUTINGPOLICYRULE] SECTION OPTIONS
An "[RoutingPolicyRule]" section accepts the following keys. Specify several "[RoutingPolicyRule]"
sections to configure several rules.
TypeOfService=
Specifies the type of service to match a number between 0 to 255.
From=
Specifies the source address prefix to match. Possibly followed by a slash and the prefix length.
To=
Specifies the destination address prefix to match. Possibly followed by a slash and the prefix
length.
FirewallMark=
Specifies the iptables firewall mark value to match (a number between 1 and 4294967295).
Table=
Specifies the routing table identifier to lookup if the rule selector matches. The table identifier
for a route (a number between 1 and 4294967295).
Priority=
Specifies the priority of this rule. Priority= is an unsigned integer. Higher number means lower
priority, and rules get processed in order of increasing number.
IncomingInterface=
Specifies incoming device to match. If the interface is loopback, the rule only matches packets
originating from this host.
OutgoingInterface=
Specifies the outgoing device to match. The outgoing interface is only available for packets
originating from local sockets that are bound to a device.
[ROUTE] SECTION OPTIONS
The "[Route]" section accepts the following keys. Specify several "[Route]" sections to configure several
routes.
Gateway=
As in the "[Network]" section.
GatewayOnlink=
The "GatewayOnlink" option tells the kernel that it does not have to check if the gateway is
reachable directly by the current machine (i.e., the kernel does not need to check if the gateway is
attached to the local network), so that we can insert the route in the kernel table without it being
complained about. A boolean, defaults to "no".
Destination=
The destination prefix of the route. Possibly followed by a slash and the prefix length. If omitted,
a full-length host route is assumed.
Source=
The source prefix of the route. Possibly followed by a slash and the prefix length. If omitted, a
full-length host route is assumed.
Metric=
The metric of the route (an unsigned integer).
IPv6Preference=
Specifies the route preference as defined in RFC4191[12] for Router Discovery messages. Which can be
one of "low" the route has a lowest priority, "medium" the route has a default priority or "high" the
route has a highest priority.
Scope=
The scope of the route, which can be "global", "link" or "host". Defaults to "global".
PreferredSource=
The preferred source address of the route. The address must be in the format described in
inet_pton(3).
Table=num
The table identifier for the route (a number between 1 and 4294967295, or 0 to unset). The table can
be retrieved using ip route show table num.
Protocol=
The Protocol identifier for the route. Takes a number between 0 and 255 or the special values
"kernel", "boot" and "static". Defaults to "static".
Type=
The Type identifier for special route types, which can be "unicast" route to a destination network
address which describes the path to the destination, "blackhole" packets are discarded silently,
"unreachable" packets are discarded and the ICMP message host unreachable is generated, "prohibit"
packets are discarded and the ICMP message communication administratively prohibited is generated.
Defaults to "unicast".
InitialCongestionWindow=
The TCP initial congestion window is used during the start of a TCP connection. During the start of a
TCP session, when a client requests a resource, the server's initial congestion window determines how
many data bytes will be sent during the initial burst of data. Takes a size in bytes between 1 and
4294967295 (2^32 - 1). The usual suffixes K, M, G are supported and are understood to the base of
1024. Defaults to unset.
InitialAdvertisedReceiveWindow=
The TCP initial advertised receive window is the amount of receive data (in bytes) that can initally
be buffered at one time on a connection. The sending host can send only that amount of data before
waiting for an acknowledgment and window update from the receiving host. Takes a size in bytes
between 1 and 4294967295 (2^32 - 1). The usual suffixes K, M, G are supported and are understood to
the base of 1024. Defaults to unset.
QuickAck=
Takes a boolean argument. When true enables TCP quick ack mode for the route. Defaults to unset.
[DHCP] SECTION OPTIONS
The "[DHCP]" section configures the DHCPv4 and DHCP6 client, if it is enabled with the DHCP= setting
described above:
UseDNS=
When true (the default), the DNS servers received from the DHCP server will be used and take
precedence over any statically configured ones.
This corresponds to the nameserver option in resolv.conf(5).
UseNTP=
When true (the default), the NTP servers received from the DHCP server will be used by
systemd-timesyncd and take precedence over any statically configured ones.
UseMTU=
When true, the interface maximum transmission unit from the DHCP server will be used on the current
link. If MTUBytes= is set, then this setting is ignored. Defaults to false.
Anonymize=
Takes a boolean argument. When true, the options sent to the DHCP server will follow the RFC 7844[13]
(Anonymity Profiles for DHCP Clients) to minimize disclosure of identifying information. Defaults to
false.
This option should only be set to true when MACAddressPolicy= is set to "random" (see
systemd.link(5)).
Note that this configuration will overwrite others. In concrete, the following variables will be
ignored: SendHostname=, ClientIdentifier=, UseRoutes=, SendHostname=, UseMTU=,
VendorClassIdentifier=, UseTimezone=.
SendHostname=
When true (the default), the machine's hostname will be sent to the DHCP server. Note that the
machine's hostname must consist only of 7-bit ASCII lower-case characters and no spaces or dots, and
be formatted as a valid DNS domain name. Otherwise, the hostname is not send even if this is set to
true.
UseHostname=
When true (the default), the hostname received from the DHCP server will be set as the transient
hostname of the system.
Hostname=
Use this value for the hostname which is sent to the DHCP server, instead of machine's hostname. Note
that the specified hostname must consist only of 7-bit ASCII lower-case characters and no spaces or
dots, and be formatted as a valid DNS domain name.
UseDomains=
Takes a boolean argument, or the special value "route". When true, the domain name received from the
DHCP server will be used as DNS search domain over this link, similar to the effect of the Domains=
setting. If set to "route", the domain name received from the DHCP server will be used for routing
DNS queries only, but not for searching, similar to the effect of the Domains= setting when the
argument is prefixed with "~". Defaults to true on Ubuntu.
It is recommended to enable this option only on trusted networks, as setting this affects resolution
of all host names, in particular of single-label names. It is generally safer to use the supplied
domain only as routing domain, rather than as search domain, in order to not have it affect local
resolution of single-label names.
When set to true, this setting corresponds to the domain option in resolv.conf(5).
UseRoutes=
When true (the default), the static routes will be requested from the DHCP server and added to the
routing table with a metric of 1024, and a scope of "global", "link" or "host", depending on the
route's destination and gateway. If the destination is on the local host, e.g., 127.x.x.x, or the
same as the link's own address, the scope will be set to "host". Otherwise if the gateway is null (a
direct route), a "link" scope will be used. For anything else, scope defaults to "global".
UseGateway=
When true, the gateway will be requested from the DHCP server and added to the routing table with a
metric of 1024, and a scope of "link". When unset, the value specified with UseRoutes= is used.
UseTimezone=
When true, the timezone received from the DHCP server will be set as timezone of the local system.
Defaults to "no".
ClientIdentifier=
The DHCPv4 client identifier to use. Either "mac" to use the MAC address of the link or "duid" (the
default, see below) to use an RFC4361-compliant Client ID.
VendorClassIdentifier=
The vendor class identifier used to identify vendor type and configuration.
DUIDType=
Override the global DUIDType setting for this network. See networkd.conf(5) for a description of
possible values.
DUIDRawData=
Override the global DUIDRawData setting for this network. See networkd.conf(5) for a description of
possible values.
IAID=
The DHCP Identity Association Identifier (IAID) for the interface, a 32-bit unsigned integer.
RequestBroadcast=
Request the server to use broadcast messages before the IP address has been configured. This is
necessary for devices that cannot receive RAW packets, or that cannot receive packets at all before
an IP address has been configured. On the other hand, this must not be enabled on networks where
broadcasts are filtered out.
RouteMetric=
Set the routing metric for routes specified by the DHCP server.
RouteTable=num
The table identifier for DHCP routes (a number between 1 and 4294967295, or 0 to unset). The table
can be retrieved using ip route show table num.
When used in combination with VRF= the VRF's routing table is used unless this parameter is
specified.
ListenPort=
Allow setting custom port for the DHCP client to listen on.
RapidCommit=
A boolean. The DHCPv6 client can obtain configuration parameters from a DHCPv6 server through a rapid
two-message exchange (solicit and reply). When the rapid commit option is enabled by both the DHCPv6
client and the DHCPv6 server, the two-message exchange is used, rather than the default four-method
exchange (solicit, advertise, request, and reply). The two-message exchange provides faster client
configuration and is beneficial in environments in which networks are under a heavy load. See RFC
3315[14] for details. Defaults to true.
[IPV6ACCEPTRA] SECTION OPTIONS
The "[IPv6AcceptRA]" section configures the IPv6 Router Advertisement (RA) client, if it is enabled with
the IPv6AcceptRA= setting described above:
UseDNS=
When true (the default), the DNS servers received in the Router Advertisement will be used and take
precedence over any statically configured ones.
This corresponds to the nameserver option in resolv.conf(5).
UseDomains=
Takes a boolean argument, or the special value "route". When true, the domain name received via IPv6
Router Advertisement (RA) will be used as DNS search domain over this link, similar to the effect of
the Domains= setting. If set to "route", the domain name received via IPv6 RA will be used for
routing DNS queries only, but not for searching, similar to the effect of the Domains= setting when
the argument is prefixed with "~". Defaults to true on Ubuntu.
It is recommended to enable this option only on trusted networks, as setting this affects resolution
of all host names, in particular of single-label names. It is generally safer to use the supplied
domain only as routing domain, rather than as search domain, in order to not have it affect local
resolution of single-label names.
When set to true, this setting corresponds to the domain option in resolv.conf(5).
RouteTable=num
The table identifier for the routes received in the Router Advertisement (a number between 1 and
4294967295, or 0 to unset). The table can be retrieved using ip route show table num.
[DHCPSERVER] SECTION OPTIONS
The "[DHCPServer]" section contains settings for the DHCP server, if enabled via the DHCPServer= option
described above:
PoolOffset=, PoolSize=
Configures the pool of addresses to hand out. The pool is a contiguous sequence of IP addresses in
the subnet configured for the server address, which does not include the subnet nor the broadcast
address. PoolOffset= takes the offset of the pool from the start of subnet, or zero to use the
default value. PoolSize= takes the number of IP addresses in the pool or zero to use the default
value. By default, the pool starts at the first address after the subnet address and takes up the
rest of the subnet, excluding the broadcast address. If the pool includes the server address (the
default), this is reserved and not handed out to clients.
DefaultLeaseTimeSec=, MaxLeaseTimeSec=
Control the default and maximum DHCP lease time to pass to clients. These settings take time values
in seconds or another common time unit, depending on the suffix. The default lease time is used for
clients that did not ask for a specific lease time. If a client asks for a lease time longer than the
maximum lease time, it is automatically shortened to the specified time. The default lease time
defaults to 1h, the maximum lease time to 12h. Shorter lease times are beneficial if the
configuration data in DHCP leases changes frequently and clients shall learn the new settings with
shorter latencies. Longer lease times reduce the generated DHCP network traffic.
EmitDNS=, DNS=
Configures whether the DHCP leases handed out to clients shall contain DNS server information. The
EmitDNS= setting takes a boolean argument and defaults to "yes". The DNS servers to pass to clients
may be configured with the DNS= option, which takes a list of IPv4 addresses. If the EmitDNS= option
is enabled but no servers configured, the servers are automatically propagated from an "uplink"
interface that has appropriate servers set. The "uplink" interface is determined by the default route
of the system with the highest priority. Note that this information is acquired at the time the lease
is handed out, and does not take uplink interfaces into account that acquire DNS or NTP server
information at a later point. DNS server propagation does not take /etc/resolv.conf into account.
Also, note that the leases are not refreshed if the uplink network configuration changes. To ensure
clients regularly acquire the most current uplink DNS server information, it is thus advisable to
shorten the DHCP lease time via MaxLeaseTimeSec= described above.
EmitNTP=, NTP=
Similar to the EmitDNS= and DNS= settings described above, these settings configure whether and what
NTP server information shall be emitted as part of the DHCP lease. The same syntax, propagation
semantics and defaults apply as for EmitDNS= and DNS=.
EmitRouter=
Similar to the EmitDNS= setting described above, this setting configures whether the DHCP lease
should contain the router option. The same syntax, propagation semantics and defaults apply as for
EmitDNS=.
EmitTimezone=, Timezone=
Configures whether the DHCP leases handed out to clients shall contain timezone information. The
EmitTimezone= setting takes a boolean argument and defaults to "yes". The Timezone= setting takes a
timezone string (such as "Europe/Berlin" or "UTC") to pass to clients. If no explicit timezone is
set, the system timezone of the local host is propagated, as determined by the /etc/localtime
symlink.
[IPV6PREFIXDELEGATION] SECTION OPTIONS
The "[IPv6PrefixDelegation]" section contains settings for sending IPv6 Router Advertisements and whether
to act as a router, if enabled via the IPv6PrefixDelegation= option described above. IPv6 network
prefixes are defined with one or more "[IPv6Prefix]" sections.
Managed=, OtherInformation=
Controls whether a DHCPv6 server is used to acquire IPv6 addresses on the network link when Managed=
boolean is set to "true" or if only additional network information can be obtained via DHCPv6 for the
network link when OtherInformation= boolean is set to "true". Both settings default to "false", which
means that a DHCPv6 server is not being used.
RouterLifetimeSec=
Configures the IPv6 router lifetime in seconds. If set, this host also announces itself in Router
Advertisements as an IPv6 router for the network link. Defaults to unset, which means the host is not
acting as a router.
RouterPreference=
Configures IPv6 router preference if RouterLifetimeSec= is non-zero. Valid values are "high",
"medium" and "low", with "normal" and "default" added as synonyms for "medium" just to make
configuration easier. See RFC 4191[12] for details. Defaults to "medium".
EmitDNS=, DNS=
DNS= specifies a list of recursive DNS server IPv6 addresses that distributed via Router
Advertisement messages when EmitDNS= is true. If DNS= is empty, DNS servers are read from the
"[Network]" section. If the "[Network]" section does not contain any DNS servers either, DNS servers
from the uplink with the highest priority default route are used. When EmitDNS= is false, no DNS
server information is sent in Router Advertisement messages. EmitDNS= defaults to true.
EmitDomains=, Domains=
A list of DNS search domains distributed via Router Advertisement messages when EmitDomains= is true.
If Domains= is empty, DNS search domains are read from the "[Network]" section. If the "[Network]"
section does not contain any DNS search domains either, DNS search domains from the uplink with the
highest priority default route are used. When EmitDomains= is false, no DNS search domain information
is sent in Router Advertisement messages. EmitDomains= defaults to true.
DNSLifetimeSec=
Lifetime in seconds for the DNS server addresses listed in DNS= and search domains listed in
Domains=.
[IPV6PREFIX] SECTION OPTIONS
One or more "[IPv6Prefix]" sections contain the IPv6 prefixes that are announced via Router
Advertisements. See RFC 4861[15] for further details.
AddressAutoconfiguration=, OnLink=
Boolean values to specify whether IPv6 addresses can be autoconfigured with this prefix and whether
the prefix can be used for onlink determination. Both settings default to "true" in order to ease
configuration.
Prefix=
The IPv6 prefix that is to be distributed to hosts. Similarly to configuring static IPv6 addresses,
the setting is configured as an IPv6 prefix and its prefix length, separated by a "/" character. Use
multiple "[IPv6Prefix]" sections to configure multiple IPv6 prefixes since prefix lifetimes, address
autoconfiguration and onlink status may differ from one prefix to another.
PreferredLifetimeSec=, ValidLifetimeSec=
Preferred and valid lifetimes for the prefix measured in seconds. PreferredLifetimeSec= defaults to
604800 seconds (one week) and ValidLifetimeSec= defaults to 2592000 seconds (30 days).
[BRIDGE] SECTION OPTIONS
The "[Bridge]" section accepts the following keys.
UnicastFlood=
A boolean. Controls whether the bridge should flood traffic for which an FDB entry is missing and the
destination is unknown through this port. Defaults to on.
HairPin=
A boolean. Configures whether traffic may be sent back out of the port on which it was received. By
default, this flag is false, and the bridge will not forward traffic back out of the receiving port.
UseBPDU=
A boolean. Configures whether STP Bridge Protocol Data Units will be processed by the bridge port.
Defaults to yes.
FastLeave=
A boolean. This flag allows the bridge to immediately stop multicast traffic on a port that receives
an IGMP Leave message. It is only used with IGMP snooping if enabled on the bridge. Defaults to off.
AllowPortToBeRoot=
A boolean. Configures whether a given port is allowed to become a root port. Only used when STP is
enabled on the bridge. Defaults to on.
Cost=
Sets the "cost" of sending packets of this interface. Each port in a bridge may have a different
speed and the cost is used to decide which link to use. Faster interfaces should have lower costs. It
is an integer value between 1 and 65535.
Priority=
Sets the "priority" of sending packets on this interface. Each port in a bridge may have a different
priority which is used to decide which link to use. Lower value means higher priority. It is an
integer value between 0 to 63. Networkd does not set any default, meaning the kernel default value of
32 is used.
[BRIDGEFDB] SECTION OPTIONS
The "[BridgeFDB]" section manages the forwarding database table of a port and accepts the following keys.
Specify several "[BridgeFDB]" sections to configure several static MAC table entries.
MACAddress=
As in the "[Network]" section. This key is mandatory.
VLANId=
The VLAN ID for the new static MAC table entry. If omitted, no VLAN ID information is appended to the
new static MAC table entry.
[BRIDGEVLAN] SECTION OPTIONS
The "[BridgeVLAN]" section manages the VLAN ID configuration of a bridge port and accepts the following
keys. Specify several "[BridgeVLAN]" sections to configure several VLAN entries. The VLANFiltering=
option has to be enabled, see "[Bridge]" section in systemd.netdev(5).
VLAN=
The VLAN ID allowed on the port. This can be either a single ID or a range M-N. VLAN IDs are valid
from 1 to 4094.
EgressUntagged=
The VLAN ID specified here will be used to untag frames on egress. Configuring EgressUntagged=
implicates the use of VLAN= above and will enable the VLAN ID for ingress as well. This can be either
a single ID or a range M-N.
PVID=
The Port VLAN ID specified here is assigned to all untagged frames at ingress. PVID= can be used
only once. Configuring PVID= implicates the use of VLAN= above and will enable the VLAN ID for
ingress as well.
EXAMPLES
Example 1. Static network configuration
# /etc/systemd/network/50-static.network
[Match]
Name=enp2s0
[Network]
Address=192.168.0.15/24
Gateway=192.168.0.1
This brings interface "enp2s0" up with a static address. The specified gateway will be used for a default
route.
Example 2. DHCP on ethernet links
# /etc/systemd/network/80-dhcp.network
[Match]
Name=en*
[Network]
DHCP=yes
This will enable DHCPv4 and DHCPv6 on all interfaces with names starting with "en" (i.e. ethernet
interfaces).
Example 3. A bridge with two enslaved links
# /etc/systemd/network/25-bridge-static.network
[Match]
Name=bridge0
[Network]
Address=192.168.0.15/24
Gateway=192.168.0.1
DNS=192.168.0.1
# /etc/systemd/network/25-bridge-slave-interface-1.network
[Match]
Name=enp2s0
[Network]
Bridge=bridge0
# /etc/systemd/network/25-bridge-slave-interface-2.network
[Match]
Name=wlp3s0
[Network]
Bridge=bridge0
This creates a bridge and attaches devices "enp2s0" and "wlp3s0" to it. The bridge will have the
specified static address and network assigned, and a default route via the specified gateway will be
added. The specified DNS server will be added to the global list of DNS resolvers.
Example 4.
# /etc/systemd/network/20-bridge-slave-interface-vlan.network
[Match]
Name=enp2s0
[Network]
Bridge=bridge0
[BridgeVLAN]
VLAN=1-32
PVID=42
EgressUntagged=42
[BridgeVLAN]
VLAN=100-200
[BridgeVLAN]
EgressUntagged=300-400
This overrides the configuration specified in the previous example for the interface "enp2s0", and
enables VLAN on that bridge port. VLAN IDs 1-32, 42, 100-400 will be allowed. Packets tagged with VLAN
IDs 42, 300-400 will be untagged when they leave on this interface. Untagged packets which arrive on this
interface will be assigned VLAN ID 42.
Example 5. Various tunnels
/etc/systemd/network/25-tunnels.network
[Match]
Name=ens1
[Network]
Tunnel=ipip-tun
Tunnel=sit-tun
Tunnel=gre-tun
Tunnel=vti-tun
/etc/systemd/network/25-tunnel-ipip.netdev
[NetDev]
Name=ipip-tun
Kind=ipip
/etc/systemd/network/25-tunnel-sit.netdev
[NetDev]
Name=sit-tun
Kind=sit
/etc/systemd/network/25-tunnel-gre.netdev
[NetDev]
Name=gre-tun
Kind=gre
/etc/systemd/network/25-tunnel-vti.netdev
[NetDev]
Name=vti-tun
Kind=vti
This will bring interface "ens1" up and create an IPIP tunnel, a SIT tunnel, a GRE tunnel, and a VTI
tunnel using it.
Example 6. A bond device
# /etc/systemd/network/30-bond1.network
[Match]
Name=bond1
[Network]
DHCP=ipv6
# /etc/systemd/network/30-bond1.netdev
[NetDev]
Name=bond1
Kind=bond
# /etc/systemd/network/30-bond1-dev1.network
[Match]
MACAddress=52:54:00:e9:64:41
[Network]
Bond=bond1
# /etc/systemd/network/30-bond1-dev2.network
[Match]
MACAddress=52:54:00:e9:64:42
[Network]
Bond=bond1
This will create a bond device "bond1" and enslave the two devices with MAC addresses 52:54:00:e9:64:41
and 52:54:00:e9:64:42 to it. IPv6 DHCP will be used to acquire an address.
Example 7. Virtual Routing and Forwarding (VRF)
Add the "bond1" interface to the VRF master interface "vrf1". This will redirect routes generated on this
interface to be within the routing table defined during VRF creation. For kernels before 4.8 traffic
won't be redirected towards the VRFs routing table unless specific ip-rules are added.
# /etc/systemd/network/25-vrf.network
[Match]
Name=bond1
[Network]
VRF=vrf1
Example 8. MacVTap
This brings up a network interface "macvtap-test" and attaches it to "enp0s25".
# /lib/systemd/network/25-macvtap.network
[Match]
Name=enp0s25
[Network]
MACVTAP=macvtap-test
SEE ALSO
systemd(1), systemd-networkd.service(8), systemd.link(5), systemd.netdev(5), systemd-resolved.service(8)
NOTES
1. Link-Local Multicast Name Resolution
https://tools.ietf.org/html/rfc4795
2. Multicast DNS
https://tools.ietf.org/html/rfc6762
3. DNSSEC
https://tools.ietf.org/html/rfc4033
4. IEEE 802.1AB-2009
http://standards.ieee.org/getieee802/download/802.1AB-2009.pdf
5. ip-sysctl.txt
https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt
6. RFC 4941
https://tools.ietf.org/html/rfc4941
7. RFC 1027
https://tools.ietf.org/html/rfc1027
8. RFC 6275
https://tools.ietf.org/html/rfc6275
9. RFC 4862
https://tools.ietf.org/html/rfc4862
10. RFC 3041
https://tools.ietf.org/html/rfc3041
11. RFC 3484
https://tools.ietf.org/html/rfc3484
12. RFC4191
https://tools.ietf.org/html/rfc4191
13. RFC 7844
https://tools.ietf.org/html/rfc7844
14. RFC 3315
https://tools.ietf.org/html/rfc3315#section-17.2.1
15. RFC 4861
https://tools.ietf.org/html/rfc4861