systemd.netdev — Virtual Network Device configuration
netdev
.netdev
Network setup is performed by systemd-networkd(8).
Virtual Network Device files must have the extension
.netdev
; other extensions are ignored.
Virtual network devices are created as soon as networkd is
started. If a netdev with the specified name already exists,
networkd will use that as-is rather than create its own. Note that
the settings of the pre-existing netdev will not be changed by
networkd.
The .netdev
files are read from the
files located in the system network directory
/usr/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 /usr/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").
The following kinds of virtual network devices may be
configured in .netdev
files:
Table 1. Supported kinds of virtual network devices
Kind | Description |
---|---|
bond | A bond device is an aggregation of all its slave devices. See Linux Ethernet Bonding Driver HOWTO for details.Local configuration |
bridge | A bridge device is a software switch, and each of its slave devices and the bridge itself are ports of the switch. |
dummy | A dummy device drops all packets sent to it. |
gre | A Level 3 GRE tunnel over IPv4. See RFC 2784 for details. |
gretap | A Level 2 GRE tunnel over IPv4. |
ip6gre | A Level 3 GRE tunnel over IPv6. |
ip6tnl | An IPv4 or IPv6 tunnel over IPv6 |
ip6gretap | An Level 2 GRE tunnel over IPv6. |
ipip | An IPv4 over IPv4 tunnel. |
ipvlan | An ipvlan device is a stacked device which receives packets from its underlying device based on IP address filtering. |
macvlan | A macvlan device is a stacked device which receives packets from its underlying device based on MAC address filtering. |
macvtap | A macvtap device is a stacked device which receives packets from its underlying device based on MAC address filtering. |
sit | An IPv6 over IPv4 tunnel. |
tap | A persistent Level 2 tunnel between a network device and a device node. |
tun | A persistent Level 3 tunnel between a network device and a device node. |
veth | An Ethernet tunnel between a pair of network devices. |
vlan | A VLAN is a stacked device which receives packets from its underlying device based on VLAN tagging. See IEEE 802.1Q for details. |
vti | An IPv4 over IPSec tunnel. |
vti6 | An IPv6 over IPSec tunnel. |
vxlan | A virtual extensible LAN (vxlan), for connecting Cloud computing deployments. |
A virtual network device is only created if the
"[Match]
" section matches the current
environment, or if the section is empty. The following keys are
accepted:
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.
Architecture=
¶Checks whether the system is running on a specific
architecture. See "ConditionArchitecture=
" in
systemd.unit(5)
for details.
The "[NetDev]
" section accepts the
following keys:
Description=
¶A free-form description of the netdev.
Name=
¶The interface name used when creating the netdev. This option is compulsory.
Kind=
¶The netdev kind. This option is compulsory. See the
"Supported netdev kinds
" section for the
valid keys.
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. This key is not
currently supported for "tun
" or
"tap
" devices.
MACAddress=
¶The MAC address to use for the device. If none is
given, one is generated based on the interface name and
the
machine-id(5).
This key is not currently supported for
"tun
" or "tap
" devices.
The "[Bridge]
" section only applies for
netdevs of kind "bridge
", and accepts the
following keys:
HelloTimeSec=
¶HelloTimeSec specifies the number of seconds between two hello packets sent out by the root bridge and the designated bridges. Hello packets are used to communicate information about the topology throughout the entire bridged local area network.
MaxAgeSec=
¶MaxAgeSec specifies the number of seconds of maximum message age. If the last seen (received) hello packet is more than this number of seconds old, the bridge in question will start the takeover procedure in attempt to become the Root Bridge itself.
ForwardDelaySec=
¶ForwardDelaySec specifies the number of seconds spent in each of the Listening and Learning states before the Forwarding state is entered.
The "[VLAN]
" section only applies for
netdevs of kind "vlan
", and accepts the
following key:
Id=
¶The VLAN ID to use. An integer in the range 0–4094. This option is compulsory.
The "[MACVLAN]
" section only applies for
netdevs of kind "macvlan
", and accepts the
following key:
Mode=
¶The MACVLAN mode to use. The supported options are
"private
",
"vepa
",
"bridge
", and
"passthru
".
The "[MACVTAP]
" section applies for
netdevs of kind "macvtap
" and accepts the
same key as "[MACVLAN].
"
The "[IPVLAN]
" section only applies for
netdevs of kind "ipvlan
", and accepts the
following key:
Mode=
¶The IPVLAN mode to use. The supported options are
"L2
" and "L3
".
The "[VXLAN]
" section only applies for
netdevs of kind "vxlan
", and accepts the
following keys:
Id=
¶The VXLAN ID to use.
Group=
¶An assigned multicast group IP address.
TOS=
¶The Type Of Service byte value for a vxlan interface.
TTL=
¶A fixed Time To Live N on Virtual eXtensible Local Area Network packets. N is a number in the range 1–255. 0 is a special value meaning that packets inherit the TTL value.
MacLearning=
¶A boolean. When true, enables dynamic MAC learning to discover remote MAC addresses.
FDBAgeingSec=
¶The lifetime of Forwarding Database entry learnt by the kernel, in seconds.
MaximumFDBEntries=
¶Configures maximum number of FDB entries.
ARPProxy=
¶A boolean. When true, enables ARP proxying.
L2MissNotification=
¶A boolean. When true, enables netlink LLADDR miss notifications.
L3MissNotification=
¶A boolean. When true, enables netlink IP address miss notifications.
RouteShortCircuit=
¶A boolean. When true, route short circuiting is turned on.
UDPCheckSum=
¶A boolean. When true, transmitting UDP checksums when doing VXLAN/IPv4 is turned on.
UDP6ZeroChecksumTx=
¶A boolean. When true, sending zero checksums in VXLAN/IPv6 is turned on.
UDP6ZeroCheckSumRx=
¶A boolean. When true, receiving zero checksums in VXLAN/IPv6 is turned on.
GroupPolicyExtension=
¶A boolean. When true, it enables Group Policy VXLAN extension security label mechanism across network peers based on VXLAN. For details about the Group Policy VXLAN, see the VXLAN Group Policy document. Defaults to false.
DestinationPort=
¶Configures the default destination UDP port on a per-device basis. If destination port is not specified then Linux kernel default will be used. Set destination port 4789 to get the IANA assigned value, and destination port 0 to get default values.
PortRange=
¶Configures VXLAN port range. VXLAN bases source UDP port based on flow to help the receiver to be able to load balance based on outer header flow. It restricts the port range to the normal UDP local ports, and allows overriding via configuration.
The "[Tunnel]
" section only applies for
netdevs of kind
"ipip
",
"sit
",
"gre
",
"gretap
",
"ip6gre
",
"ip6gretap
",
"vti
",
"vti6
", and
"ip6tnl
" and accepts
the following keys:
Local=
¶A static local address for tunneled packets. It must be an address on another interface of this host.
Remote=
¶The remote endpoint of the tunnel.
TOS=
¶The Type Of Service byte value for a tunnel interface. For details about the TOS, see the Type of Service in the Internet Protocol Suite document.
TTL=
¶A fixed Time To Live N on tunneled packets. N is a number in the range 1–255. 0 is a special value meaning that packets inherit the TTL value. The default value for IPv4 tunnels is: inherit. The default value for IPv6 tunnels is 64.
DiscoverPathMTU=
¶A boolean. When true, enables Path MTU Discovery on the tunnel.
IPv6FlowLabel=
¶Configures the 20-bit flow label (see
RFC 6437) field in the IPv6 header (see
RFC 2460), which is used by a node to label packets of a flow.
It is only used for IPv6 tunnels.
A flow label of zero is used to indicate packets that have
not been labeled.
It can be configured to a value in the range 0–0xFFFFF, or be
set to "inherit
", in which case the original flowlabel is used.
CopyDSCP=
¶A boolean. When true, the Differentiated Service Code
Point (DSCP) field will be copied to the inner header from
outer header during the decapsulation of an IPv6 tunnel
packet. DSCP is a field in an IP packet that enables different
levels of service to be assigned to network traffic.
Defaults to "no
".
EncapsulationLimit=
¶The Tunnel Encapsulation Limit option specifies how many additional
levels of encapsulation are permitted to be prepended to the packet.
For example, a Tunnel Encapsulation Limit option containing a limit
value of zero means that a packet carrying that option may not enter
another tunnel before exiting the current tunnel.
(see RFC 2473).
The valid range is 0–255 and "none
". Defaults to 4.
Mode=
¶An "ip6tnl
" tunnel can be in one of three
modes
"ip6ip6
" for IPv6 over IPv6,
"ipip6
" for IPv4 over IPv6 or
"any
" for either.
The "[Peer]
" section only applies for
netdevs of kind "veth
" and accepts the
following keys:
The "[Tun]
" section only applies for
netdevs of kind "tun
", and accepts the following
keys:
OneQueue=
¶Takes a boolean argument. Configures whether
all packets are queued at the device (enabled), or a fixed
number of packets are queued at the device and the rest at the
"qdisc
". Defaults to
"no
".
MultiQueue=
¶Takes a boolean argument. Configures whether
to use multiple file descriptors (queues) to parallelize
packets sending and receiving. Defaults to
"no
".
PacketInfo=
¶Takes a boolean argument. Configures whether
packets should be prepended with four extra bytes (two flag
bytes and two protocol bytes). If disabled, it indicates that
the packets will be pure IP packets. Defaults to
"no
".
VNetHeader=
¶Takes a boolean argument. Configures
IFF_VNET_HDR flag for a tap device. It allows sending
and receiving larger Generic Segmentation Offload (GSO)
packets. This may increase throughput significantly.
Defaults to
"no
".
User=
¶User to grant access to the
/dev/net/tun
device.
Group=
¶Group to grant access to the
/dev/net/tun
device.
The "[Tap]
" section only applies for
netdevs of kind "tap
", and accepts the same keys
as the "[Tun]
" section.
The "[Bond]
" section accepts the following
key:
Mode=
¶Specifies one of the bonding policies. The default is
"balance-rr
" (round robin). Possible values are
"balance-rr
",
"active-backup
",
"balance-xor
",
"broadcast
",
"802.3ad
",
"balance-tlb
", and
"balance-alb
".
TransmitHashPolicy=
¶Selects the transmit hash policy to use for slave
selection in balance-xor, 802.3ad, and tlb modes. Possible
values are
"layer2
",
"layer3+4
",
"layer2+3
",
"encap2+3
",
"802.3ad
", and
"encap3+4
".
LACPTransmitRate=
¶Specifies the rate with which link partner transmits
Link Aggregation Control Protocol Data Unit packets in
802.3ad mode. Possible values are "slow
",
which requests partner to transmit LACPDUs every 30 seconds,
and "fast
", which requests partner to
transmit LACPDUs every second. The default value is
"slow
".
MIIMonitorSec=
¶Specifies the frequency that Media Independent Interface link monitoring will occur. A value of zero disables MII link monitoring. This value is rounded down to the nearest millisecond. The default value is 0.
UpDelaySec=
¶Specifies the delay before a link is enabled after a link up status has been detected. This value is rounded down to a multiple of MIIMonitorSec. The default value is 0.
DownDelaySec=
¶Specifies the delay before a link is disabled after a link down status has been detected. This value is rounded down to a multiple of MIIMonitorSec. The default value is 0.
LearnPacketIntervalSec=
¶Specifies the number of seconds between instances where the bonding driver sends learning packets to each slave peer switch. The valid range is 1–0x7fffffff; the default value is 1. This option has an effect only for the balance-tlb and balance-alb modes.
AdSelect=
¶Specifies the 802.3ad aggregation selection logic to use. Possible values are
"stable
",
"bandwidth
" and
"count
".
FailOverMACPolicy=
¶Specifies whether the active-backup mode should set all slaves to
the same MAC address at the time of enslavement or, when enabled, to perform special handling of the
bond's MAC address in accordance with the selected policy. The default policy is none.
Possible values are
"none
",
"active
" and
"follow
".
ARPValidate=
¶Specifies whether or not ARP probes and replies should be
validated in any mode that supports ARP monitoring, or whether
non-ARP traffic should be filtered (disregarded) for link
monitoring purposes. Possible values are
"none
",
"active
",
"backup
" and
"all
".
ARPIntervalSec=
¶Specifies the ARP link monitoring frequency in milliseconds. A value of 0 disables ARP monitoring. The default value is 0.
ARPIPTargets=
¶Specifies the IP addresses to use as ARP monitoring peers when ARPIntervalSec is greater than 0. These are the targets of the ARP request sent to determine the health of the link to the targets. Specify these values in IPv4 dotted decimal format. At least one IP address must be given for ARP monitoring to function. The maximum number of targets that can be specified is 16. The default value is no IP addresses.
ARPAllTargets=
¶Specifies the quantity of ARPIPTargets that must be reachable
in order for the ARP monitor to consider a slave as being up.
This option affects only active-backup mode for slaves with
ARPValidate enabled. Possible values are
"any
" and
"all
".
PrimaryReselectPolicy=
¶Specifies the reselection policy for the primary slave. This
affects how the primary slave is chosen to become the active slave
when failure of the active slave or recovery of the primary slave
occurs. This option is designed to prevent flip-flopping between
the primary slave and other slaves. Possible values are
"always
",
"better
" and
"failure
".
ResendIGMP=
¶Specifies the number of IGMP membership reports to be issued after a failover event. One membership report is issued immediately after the failover, subsequent packets are sent in each 200ms interval. The valid range is 0–255. Defaults to 1. A value of 0 prevents the IGMP membership report from being issued in response to the failover event.
PacketsPerSlave=
¶Specify the number of packets to transmit through a slave before moving to the next one. When set to 0, then a slave is chosen at random. The valid range is 0–65535. Defaults to 1. This option only has effect when in balance-rr mode.
GratuitousARP=
¶Specify the number of peer notifications (gratuitous ARPs and unsolicited IPv6 Neighbor Advertisements) to be issued after a failover event. As soon as the link is up on the new slave, a peer notification is sent on the bonding device and each VLAN sub-device. This is repeated at each link monitor interval (ARPIntervalSec or MIIMonitorSec, whichever is active) if the number is greater than 1. The valid range is 0–255. The default value is 1. These options affect only the active-backup mode.
AllSlavesActive=
¶A boolean. Specifies that duplicate frames (received on inactive ports) should be dropped when false, or delivered when true. Normally, bonding will drop duplicate frames (received on inactive ports), which is desirable for most users. But there are some times it is nice to allow duplicate frames to be delivered. The default value is false (drop duplicate frames received on inactive ports).
MinLinks=
¶Specifies the minimum number of links that must be active before asserting carrier. The default value is 0.
For more detail information see Linux Ethernet Bonding Driver HOWTO
Example 2. /etc/systemd/network/25-vlan1.netdev
[Match] Virtualization=no [NetDev] Name=vlan1 Kind=vlan [VLAN] Id=1
Example 3. /etc/systemd/network/25-ipip.netdev
[NetDev] Name=ipip-tun Kind=ipip MTUBytes=1480 [Tunnel] Local=192.168.223.238 Remote=192.169.224.239 TTL=64
Example 4. /etc/systemd/network/25-tap.netdev
[NetDev] Name=tap-test Kind=tap [Tap] MultiQueue=true PacketInfo=true
Example 5. /etc/systemd/network/25-sit.netdev
[NetDev] Name=sit-tun Kind=sit MTUBytes=1480 [Tunnel] Local=10.65.223.238 Remote=10.65.223.239
Example 6. /etc/systemd/network/25-gre.netdev
[NetDev] Name=gre-tun Kind=gre MTUBytes=1480 [Tunnel] Local=10.65.223.238 Remote=10.65.223.239
Example 7. /etc/systemd/network/25-vti.netdev
[NetDev] Name=vti-tun Kind=vti MTUBytes=1480 [Tunnel] Local=10.65.223.238 Remote=10.65.223.239
Example 8. /etc/systemd/network/25-veth.netdev
[NetDev] Name=veth-test Kind=veth [Peer] Name=veth-peer
Example 9. /etc/systemd/network/25-bond.netdev
[NetDev] Name=bond1 Kind=bond [Bond] Mode=802.3ad TransmitHashPolicy=layer3+4 MIIMonitorSec=1s LACPTransmitRate=fast
Example 10. /etc/systemd/network/25-dummy.netdev
[NetDev] Name=dummy-test Kind=dummy MACAddress=12:34:56:78:9a:bc