The [Link] section accepts the following keys:
Description=
A description of the device.
Alias=
The ifalias interface property is set to this value.
MACAddressPolicy=
The policy by which the MAC address should be set. The
available policies are:
persistent
If the hardware has a persistent MAC address, as most
hardware should, and if it is used by the kernel, nothing
is done. Otherwise, a new MAC address is generated which
is guaranteed to be the same on every boot for the given
machine and the given device, but which is otherwise
random. This feature depends on ID_NET_NAME_* properties
to exist for the link. On hardware where these properties
are not set, the generation of a persistent MAC address
will fail.
random
If the kernel is using a random MAC address, nothing is
done. Otherwise, a new address is randomly generated each
time the device appears, typically at boot. Either way,
the random address will have the "unicast" and "locally
administered" bits set.
none
Keeps the MAC address assigned by the kernel. Or use the
MAC address specified in MACAddress=.
An empty string assignment is equivalent to setting "none".
MACAddress=
The interface MAC address to use. For this setting to take
effect, MACAddressPolicy= must either be unset, empty, or
"none".
NamePolicy=
An ordered, space-separated list of policies by which the
interface name should be set. NamePolicy= may be disabled by
specifying net.ifnames=0 on the kernel command line. Each of
the policies may fail, and the first successful one is used.
The name is not set directly, but is exported to udev as the
property ID_NET_NAME, which is, by default, used by a
udev(7), rule to set NAME. The available policies are:
kernel
If the kernel claims that the name it has set for a
device is predictable, then no renaming is performed.
database
The name is set based on entries in the udev's Hardware
Database with the key ID_NET_NAME_FROM_DATABASE.
onboard
The name is set based on information given by the
firmware for on-board devices, as exported by the udev
property ID_NET_NAME_ONBOARD. See
systemd.net-naming-scheme(7).
slot
The name is set based on information given by the
firmware for hot-plug devices, as exported by the udev
property ID_NET_NAME_SLOT. See
systemd.net-naming-scheme(7).
path
The name is set based on the device's physical location,
as exported by the udev property ID_NET_NAME_PATH. See
systemd.net-naming-scheme(7).
mac
The name is set based on the device's persistent MAC
address, as exported by the udev property
ID_NET_NAME_MAC. See systemd.net-naming-scheme(7).
keep
If the device already had a name given by userspace (as
part of creation of the device or a rename), keep it.
Name=
The interface name to use. This option has lower precedence
than NamePolicy=, so for this setting to take effect,
NamePolicy= must either be unset, empty, disabled, or all
policies configured there must fail. Also see the example
below with "Name=dmz0".
Note that specifying a name that the kernel might use for
another interface (for example "eth0") is dangerous because
the name assignment done by udev will race with the
assignment done by the kernel, and only one interface may use
the name. Depending on the order of operations, either udev
or the kernel will win, making the naming unpredictable. It
is best to use some different prefix, for example
"internal0"/"external0" or "lan0"/"lan1"/"lan3".
AlternativeNamesPolicy=
A space-separated list of policies by which the interface's
alternative names should be set. Each of the policies may
fail, and all successful policies are used. The available
policies are "database", "onboard", "slot", "path", and
"mac". If the kernel does not support the alternative names,
then this setting will be ignored.
AlternativeName=
The alternative interface name to use. This option can be
specified multiple times. If the empty string is assigned to
this option, the list is reset, and all prior assignments
have no effect. If the kernel does not support the
alternative names, then this setting will be ignored.
TransmitQueues=
Specifies the device's number of transmit queues. An integer
in the range 1...4096. When unset, the kernel's default will
be used.
ReceiveQueues=
Specifies the device's number of receive queues. An integer
in the range 1...4096. When unset, the kernel's default will
be used.
TransmitQueueLength=
Specifies the transmit queue length of the device in number
of packets. An unsigned integer in the range 0...4294967294.
When unset, the kernel's default will be used.
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.
BitsPerSecond=
The speed to set for the device, the value is rounded down to
the nearest Mbps. The usual suffixes K, M, G are supported
and are understood to the base of 1000.
Duplex=
The duplex mode to set for the device. The accepted values
are half and full.
AutoNegotiation=
Takes a boolean. If set to yes, automatic negotiation of
transmission parameters is enabled. Autonegotiation is a
procedure by which two connected ethernet devices choose
common transmission parameters, such as speed, duplex mode,
and flow control. When unset, the kernel's default will be
used.
Note that if autonegotiation is enabled, speed and duplex
settings are read-only. If autonegotiation is disabled, speed
and duplex settings are writable if the driver supports
multiple link modes.
WakeOnLan=
The Wake-on-LAN policy to set for the device. Takes the
special value "off" which disables Wake-on-LAN, or space
separated list of the following words:
phy
Wake on PHY activity.
unicast
Wake on unicast messages.
multicast
Wake on multicast messages.
broadcast
Wake on broadcast messages.
arp
Wake on ARP.
magic
Wake on receipt of a magic packet.
secureon
Enable secureon(tm) password for MagicPacket(tm).
Defaults to unset, and the device's default will be used.
This setting can be specified multiple times. If an empty
string is assigned, then the all previous assignments are
cleared.
Port=
The port option is used to select the device port. The
supported values are:
tp
An Ethernet interface using Twisted-Pair cable as the
medium.
aui
Attachment Unit Interface (AUI). Normally used with hubs.
bnc
An Ethernet interface using BNC connectors and co-axial
cable.
mii
An Ethernet interface using a Media Independent Interface
(MII).
fibre
An Ethernet interface using Optical Fibre as the medium.
Advertise=
This sets what speeds and duplex modes of operation are
advertised for auto-negotiation. This implies
"AutoNegotiation=yes". The supported values are:
Table 1. Supported advertise values
┌───────────────────┬──────────────┬─────────────┐
│Advertise │ Speed (Mbps) │ Duplex Mode │
├───────────────────┼──────────────┼─────────────┤
│10baset-half │ 10 │ half │
├───────────────────┼──────────────┼─────────────┤
│10baset-full │ 10 │ full │
├───────────────────┼──────────────┼─────────────┤
│100baset-half │ 100 │ half │
├───────────────────┼──────────────┼─────────────┤
│100baset-full │ 100 │ full │
├───────────────────┼──────────────┼─────────────┤
│1000baset-half │ 1000 │ half │
├───────────────────┼──────────────┼─────────────┤
│1000baset-full │ 1000 │ full │
├───────────────────┼──────────────┼─────────────┤
│10000baset-full │ 10000 │ full │
├───────────────────┼──────────────┼─────────────┤
│2500basex-full │ 2500 │ full │
├───────────────────┼──────────────┼─────────────┤
│1000basekx-full │ 1000 │ full │
├───────────────────┼──────────────┼─────────────┤
│10000basekx4-full │ 10000 │ full │
├───────────────────┼──────────────┼─────────────┤
│10000basekr-full │ 10000 │ full │
├───────────────────┼──────────────┼─────────────┤
│10000baser-fec │ 10000 │ full │
├───────────────────┼──────────────┼─────────────┤
│20000basemld2-full │ 20000 │ full │
├───────────────────┼──────────────┼─────────────┤
│20000basekr2-full │ 20000 │ full │
└───────────────────┴──────────────┴─────────────┘
By default this is unset, i.e. all possible modes will be
advertised. This option may be specified more than once, in
which case all specified speeds and modes are advertised. If
the empty string is assigned to this option, the list is
reset, and all prior assignments have no effect.
ReceiveChecksumOffload=
Takes a boolean. If set to true, hardware offload for
checksumming of ingress network packets is enabled. When
unset, the kernel's default will be used.
TransmitChecksumOffload=
Takes a boolean. If set to true, hardware offload for
checksumming of egress network packets is enabled. When
unset, the kernel's default will be used.
TCPSegmentationOffload=
Takes a boolean. If set to true, TCP Segmentation Offload
(TSO) is enabled. When unset, the kernel's default will be
used.
TCP6SegmentationOffload=
Takes a boolean. If set to true, TCP6 Segmentation Offload
(tx-tcp6-segmentation) is enabled. When unset, the kernel's
default will be used.
GenericSegmentationOffload=
Takes a boolean. If set to true, Generic Segmentation Offload
(GSO) is enabled. When unset, the kernel's default will be
used.
GenericReceiveOffload=
Takes a boolean. If set to true, Generic Receive Offload
(GRO) is enabled. When unset, the kernel's default will be
used.
GenericReceiveOffloadHardware=
Takes a boolean. If set to true, hardware accelerated Generic
Receive Offload (GRO) is enabled. When unset, the kernel's
default will be used.
LargeReceiveOffload=
Takes a boolean. If set to true, Large Receive Offload (LRO)
is enabled. When unset, the kernel's default will be used.
RxChannels=, TxChannels=, OtherChannels=, CombinedChannels=
Specifies the number of receive, transmit, other, or combined
channels, respectively. Takes an unsigned integer in the
range 1...4294967295 or "max". If set to "max", the
advertised maximum value of the hardware will be used. When
unset, the number will not be changed. Defaults to unset.
RxBufferSize=, RxMiniBufferSize=, RxJumboBufferSize=,
TxBufferSize=
Specifies the maximum number of pending packets in the NIC
receive buffer, mini receive buffer, jumbo receive buffer, or
transmit buffer, respectively. Takes an unsigned integer in
the range 1...4294967295 or "max". If set to "max", the
advertised maximum value of the hardware will be used. When
unset, the number will not be changed. Defaults to unset.
RxFlowControl=
Takes a boolean. When set, enables receive flow control, also
known as the ethernet receive PAUSE message (generate and
send ethernet PAUSE frames). When unset, the kernel's default
will be used.
TxFlowControl=
Takes a boolean. When set, enables transmit flow control,
also known as the ethernet transmit PAUSE message (respond to
received ethernet PAUSE frames). When unset, the kernel's
default will be used.
AutoNegotiationFlowControl=
Takes a boolean. When set, auto negotiation enables the
interface to exchange state advertisements with the connected
peer so that the two devices can agree on the ethernet PAUSE
configuration. When unset, the kernel's default will be used.
GenericSegmentOffloadMaxBytes=
Specifies the maximum size of a Generic Segment Offload (GSO)
packet the device should accept. The usual suffixes K, M, G
are supported and are understood to the base of 1024. An
unsigned integer in the range 1...65536. Defaults to unset.
GenericSegmentOffloadMaxSegments=
Specifies the maximum number of Generic Segment Offload (GSO)
segments the device should accept. An unsigned integer in the
range 1...65535. Defaults to unset.
UseAdaptiveRxCoalesce=, UseAdaptiveTxCoalesce=
Boolean properties that, when set, enable/disable adaptive
Rx/Tx coalescing if the hardware supports it. When unset, the
kernel's default will be used.
RxCoalesceSec=, RxCoalesceIrqSec=, RxCoalesceLowSec=,
RxCoalesceHighSec=, TxCoalesceSec=, TxCoalesceIrqSec=,
TxCoalesceLowSec=, TxCoalesceHighSec=
These properties configure the delay before Rx/Tx interrupts
are generated after a packet is sent/received. The "Irq"
properties come into effect when the host is servicing an
IRQ. The "Low" and "High" properties come into effect when
the packet rate drops below the low packet rate threshold or
exceeds the high packet rate threshold respectively if
adaptive Rx/Tx coalescing is enabled. When unset, the
kernel's defaults will be used.
RxMaxCoalescedFrames=, RxMaxCoalescedIrqFrames=,
RxMaxCoalescedLowFrames=, RxMaxCoalescedHighFrames=,
TxMaxCoalescedFrames=, TxMaxCoalescedIrqFrames=,
TxMaxCoalescedLowFrames=, TxMaxCoalescedHighFrames=
These properties configure the maximum number of frames that
are sent/received before a Rx/Tx interrupt is generated. The
"Irq" properties come into effect when the host is servicing
an IRQ. The "Low" and "High" properties come into effect when
the packet rate drops below the low packet rate threshold or
exceeds the high packet rate threshold respectively if
adaptive Rx/Tx coalescing is enabled. When unset, the
kernel's defaults will be used.
CoalescePacketRateLow=, CoalescePacketRateHigh=
These properties configure the low and high packet rate
(expressed in packets per second) threshold respectively and
are used to determine when the corresponding coalescing
settings for low and high packet rates come into effect if
adaptive Rx/Tx coalescing is enabled. If unset, the kernel's
defaults will be used.
CoalescePacketRateSampleIntervalSec=
Configures how often to sample the packet rate used for
adaptive Rx/Tx coalescing. This property cannot be zero. This
lowest time granularity supported by this property is
seconds. Partial seconds will be rounded up before being
passed to the kernel. If unset, the kernel's default will be
used.
StatisticsBlockCoalesceSec=
How long to delay driver in-memory statistics block updates.
If the driver does not have an in-memory statistic block,
this property is ignored. This property cannot be zero. If
unset, the kernel's default will be used.
