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=
Takes a boolean. If set to true, the ARP (low-level Address
Resolution Protocol) for this interface is enabled. When
unset, the kernel's 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. Defaults
to unset.
Multicast=
Takes a boolean. If set to true, the multicast flag on the
device is enabled. Defaults to unset.
AllMulticast=
Takes a boolean. If set to true, the driver retrieves all
multicast packets from the network. This happens when
multicast routing is enabled. Defaults to unset.
Promiscuous=
Takes a boolean. If set to true, promiscuous mode of the
interface is enabled. Defaults to unset.
If this is set to false for the underlying link of a
"passthru" mode MACVLAN/MACVTAP, the virtual interface will
be created with the "nopromisc" flag set.
Unmanaged=
Takes 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.
Group=
Link groups are similar to port ranges found in managed
switches. When network interfaces are added to a numbered
group, operations on all the interfaces from that group can
be performed at once. Takes an unsigned integer in the range
0...4294967295. Defaults to unset.
RequiredForOnline=
Takes a boolean or a minimum operational state and an
optional maximum operational state. Please see networkctl(1)
for possible operational states. When "yes", the network is
deemed required when determining whether the system is online
(including when running systemd-networkd-wait-online). When
"no", the network is ignored when determining the online
state. When a minimum operational state and an optional
maximum operational state are set, "yes" is implied, and this
controls the minimum and maximum operational state required
for the network interface to be considered online.
Defaults to "yes" when ActivationPolicy= is not set, or set
to "up", "always-up", or "bound". Defaults to "no" when
ActivationPolicy= is set to "manual" or "down". This is
forced to "no" when ActivationPolicy= is set to
"always-down".
The network will be brought up normally (as configured by
ActivationPolicy=), 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=no".
RequiredFamilyForOnline=
Takes an address family. When specified, an IP address in the
given family is deemed required when determining whether the
link is online (including when running
systemd-networkd-wait-online). Takes one of "ipv4", "ipv6",
"both", or "any". Defaults to "any". Note that this option
has no effect if "RequiredForOnline=no", or if
"RequiredForOnline=" specifies a minimum operational state
below "degraded".
ActivationPolicy=
Specifies the policy for systemd-networkd managing the link
administrative state. Specifically, this controls how
systemd-networkd changes the network device's "IFF_UP" flag,
which is sometimes controlled by system administrators by
running e.g., ip set dev eth0 up or ip set dev eth0 down, and
can also be changed with networkctl up eth0 or networkctl
down eth0.
Takes one of "up", "always-up", "manual", "always-down",
"down", or "bound". When "manual", systemd-networkd will not
change the link's admin state automatically; the system
administrator must bring the interface up or down manually,
as desired. When "up" (the default) or "always-up", or "down"
or "always-down", systemd-networkd will set the link up or
down, respectively, when the interface is (re)configured.
When "always-up" or "always-down", systemd-networkd will set
the link up or down, respectively, any time systemd-networkd
detects a change in the administrative state. When
BindCarrier= is also set, this is automatically set to
"bound" and any other value is ignored.
When the policy is set to "down" or "manual", the default
value of RequiredForOnline= is "no". When the policy is set
to "always-down", the value of RequiredForOnline= forced to
"no".
The administrative state is not the same as the carrier
state, so using "always-up" does not mean the link will never
lose carrier. The link carrier depends on both the
administrative state as well as the network device's physical
connection. However, to avoid reconfiguration failures, when
using "always-up", IgnoreCarrierLoss= is forced to true.
