ifconfig(8) BSD System Manager's Manual ifconfig(8)
NAME
ifconfig -- configure network interface parameters
SYNOPSIS
ifconfig [-L] [-m] interface [create] [address_family]
[address[/prefixlength] [dest_address]] [parameters]
ifconfig interface destroy
ifconfig -a [-L] [-d] [-m] [-u] [address_family]
ifconfig -l [-d] [-u] [address_family]
ifconfig [-L] [-b] [-d] [-m] [-u]
ifconfig interface vlan vlan-tag vlandev iface
ifconfig interface -vlandev iface
ifconfig interface bonddev iface
ifconfig interface -bonddev iface
ifconfig interface bondmode lacp | static
DESCRIPTION
Ifconfig is used to assign an address to a network interface and/or con-
figure network interface parameters. Ifconfig must be used at boot time
to define the network address of each interface present on a machine; it
may also be used at a later time to redefine an interface's address or
other operating parameters.
The following options are available:
address
For the DARPA-Internet family, the address is either a host name
present in the host name data base, hosts(5), or a DARPA Internet
address expressed in the Internet standard ``dot notation''.
It is also possible to use the CIDR notation (also known as the
slash notation) to include the netmask. That is, one can specify
an address like 192.168.0.1/16.
address_family
Specify the address family which affects interpretation of the
remaining parameters. Since an interface can receive transmis-
sions in differing protocols with different naming schemes, spec-
ifying the address family is recommended. The address or proto-
col families currently supported are ``inet'', ``inet6'',
dest_address
Specify the address of the correspondent on the other end of a
point to point link.
interface
This parameter is a string of the form ``name unit'', for exam-
ple, ``en0''.
iface This parameter has the same encoding as the interface parameter.
The following parameters may be set with ifconfig:
add Another name for the alias parameter. Introduced for compatibil-
ity with BSD/OS.
alias Establish an additional network address for this interface. This
is sometimes useful when changing network numbers, and one wishes
to accept packets addressed to the old interface. If the address
is on the same subnet as the first network address for this
interface, a netmask of 0xffffffff has to be specified.
-alias Remove the network address specified. This would be used if you
incorrectly specified an alias, or it was no longer needed. If
you have incorrectly set an NS address having the side effect of
specifying the host portion, removing all NS addresses will allow
you to respecify the host portion.
anycast
(Inet6 only.) Specify that the address configured is an anycast
address. Based on the current specification, only routers may
configure anycast addresses. Anycast address will not be used as
source address of any of outgoing IPv6 packets.
arp Enable the use of the Address Resolution Protocol (arp(4)) in
mapping between network level addresses and link level addresses
(default). This is currently implemented for mapping between
DARPA Internet addresses and IEEE 802 48-bit MAC addresses (Eth-
ernet, FDDI, and Token Ring addresses).
-arp Disable the use of the Address Resolution Protocol (arp(4)).
bonddev iface
If the interface is a bond pseudo device, associate physical
interface iface with it. By default, the bond pseudo device is
in LACP (Link Aggregation Control Protocol) mode (see bondmode
below). In this mode, the device conforms to the IEEE 802.3ad
Link Aggregation specification.
If this is the first physical interface to be associated with the
bond interface, the bond interface inherits the ethernet address
from the physical interface. Physical interfaces that are added
to the bond have their ethernet address re-programmed so that all
members of the bond have the same ethernet address. If the phys-
ical interface is subsequently removed from the bond using
-bonddev, a new ethernet address is chosen from the remaining
interfaces, and all interfaces are re-programmed again with the
new ethernet address. If no remaining interfaces exist, the bond
interface's ethernet address is cleared.
If the specified physical interface iface is not capable of hav-
ing its ethernet address re-programmed, the bonddev command will
fail.
Once the physical interface iface is successfully associated with
the bond interface, all received packets are diverted to the bond
interface. The physical interface is no longer useable on its
own, and remains that way until it is removed from the bond using
-bonddev.
It is possible that the specified interface iface is not capable
of aggregating, and may remain unused until the operating condi-
tions change.
The link status of the bond interface depends on the state of
link aggregation. If no active partner is detected, the link
status will remain inactive.
To monitor the 802.3ad Link Aggregation state, use the -b option.
A physical interface that is associated with a vlan pseudo device
cannot at the same time be associated with a bond pseudo device.
A physical interface cannot be associated with more than one bond
pseudo device at the same time.
It is not possible to associate a bond with pseudo interfaces
such as vlan. Only physical ethernet interfaces may be associ-
ated with a bond.
-bonddev iface
If the interface is a bond pseudo device, disassociate the physi-
cal interface iface from it. Before the interface is removed
from the bond, the bond device announces to the link partner that
the interface is now individual and no longer aggregatable. If
the physical iface is the last interface in the bond, the bond
interface clears its link address.
bondmode lacp | static
If the interface is a bond pseudo device, this option will set
the mode on the bond interface. The two currently supported
modes are lacp and static. The default mode is lacp.
To enable static mode (and turn off LACP), specify static. In
static mode, a member interface is made an active part of the
link aggregate as long as the link status is active.
To re-enable LACP mode, specify lacp.
broadcast
(Inet only.) Specify the address to use to represent broadcasts
to the network. The default broadcast address is the address
with a host part of all 1's.
debug Enable driver dependent debugging code; usually, this turns on
extra console error logging.
-debug Disable driver dependent debugging code.
delete Another name for the -alias parameter.
down Mark an interface ``down''. When an interface is marked
``down'', the system will not attempt to transmit messages
through that interface. If possible, the interface will be reset
to disable reception as well. This action does not automatically
disable routes using the interface.
ether Another name for the lladdr parameter.
lladdr addr
Set the link-level address on an interface. This can be used to
e.g. set a new MAC address on an ethernet interface, though the
mechanism used is not ethernet-specific. The address addr is
specified as a series of colon-separated hex digits. If the
interface is already up when this option is used, it will be
briefly brought down and then brought back up again in order to
ensure that the receive filter in the underlying ethernet hard-
ware is properly reprogrammed.
media type
If the driver supports the media selection system, set the media
type of the interface to type. Some interfaces support the mutu-
ally exclusive use of one of several different physical media
connectors. For example, a 10Mb/s Ethernet interface might sup-
port the use of either AUI or twisted pair connectors. Setting
the media type to ``10base5/AUI'' would change the currently
active connector to the AUI port. Setting it to ``10baseT/UTP''
would activate twisted pair. Refer to the interfaces' driver
specific documentation or man page for a complete list of the
available types.
mediaopt opts
If the driver supports the media selection system, set the speci-
fied media options on the interface. The opts argument is a
comma delimited list of options to apply to the interface. Refer
to the interfaces' driver specific man page for a complete list
of available options.
-mediaopt opts
If the driver supports the media selection system, disable the
specified media options on the interface.
tunnel src_addr dest_addr
(IP tunnel devices only.) Configure the physical source and des-
tination address for IP tunnel interfaces (gif(4)). The argu-
ments src_addr and dest_addr are interpreted as the outer
source/destination for the encapsulating IPv4/IPv6 header.
deletetunnel
Unconfigure the physical source and destination address for IP
tunnel interfaces previously configured with tunnel.
create Create the specified network pseudo-device. If the interface is
given without a unit number, try to create a new device with an
arbitrary unit number. If creation of an arbitrary device is
successful, the new device name is printed to standard output.
destroy
Destroy the specified network pseudo-device.
plumb Another name for the create parameter. Included for Solaris com-
patibility.
unplumb
Another name for the destroy parameter. Included for Solaris
compatibility.
metric n
Set the routing metric of the interface to n, default 0. The
routing metric is used by the routing protocol (routed(8)).
Higher metrics have the effect of making a route less favorable;
metrics are counted as addition hops to the destination network
or host.
mtu n Set the maximum transmission unit of the interface to n, default
is interface specific. The MTU is used to limit the size of
packets that are transmitted on an interface. Not all interfaces
support setting the MTU, and some interfaces have range restric-
tions.
netmask mask
(Inet only.) Specify how much of the address to reserve for sub-
dividing networks into sub-networks. The mask includes the net-
work part of the local address and the subnet part, which is
taken from the host field of the address. The mask can be speci-
fied as a single hexadecimal number with a leading `0x', with a
dot-notation Internet address, or with a pseudo-network name
listed in the network table networks(5). The mask contains 1's
for the bit positions in the 32-bit address which are to be used
for the network and subnet parts, and 0's for the host part. The
mask should contain at least the standard network portion, and
the subnet field should be contiguous with the network portion.
The netmask can also be specified in CIDR notation after the
address. See the address option above for more information.
prefixlen len
(Inet6 only.) Specify that len bits are reserved for subdividing
networks into sub-networks. The len must be integer, and for
syntactical reason it must be between 0 to 128. It is almost
always 64 under the current IPv6 assignment rule. If the parame-
ter is omitted, 64 is used.
remove Another name for the -alias parameter. Introduced for compati-
bility with BSD/OS.
link[0-2]
Enable special processing of the link level of the interface.
These three options are interface specific in actual effect, how-
ever, they are in general used to select special modes of opera-
tion. An example of this is to enable SLIP compression, or to
select the connector type for some Ethernet cards. Refer to the
man page for the specific driver for more information.
-link[0-2]
Disable special processing at the link level with the specified
interface.
up Mark an interface ``up''. This may be used to enable an inter-
face after an ``ifconfig down''. It happens automatically when
setting the first address on an interface. If the interface was
reset when previously marked down, the hardware will be re-ini-
tialized.
vlan vlan_tag vlandev iface
If the interface is a vlan pseudo interface, set its vlan tag
value to vlan_tag and associate it with the physical interface
iface.
The vlan_tag value is a 16-bit number that is used to create an
802.1Q vlan header for packets sent from the vlan interface.
A packet that is transmitted through the vlan interface is sent
using the specified physical interface iface with 802.1Q vlan
encapsulation with the specified vlan_tag. A packet with 802.1Q
encapsulation received by the physical interface is directed to
the associated vlan interface with the matching vlan_tag. If
there is no matching vlan interface, the packet is dropped.
The vlan interface is assigned a copy of the parent interface's
flags and the parent's ethernet address. If the vlan interface
already has a physical interface associated with it, this command
will fail. To change the association to another physical inter-
face, the existing association must be cleared first using
-vlandev.
If the physical interface supports 802.1Q VLAN tagging in hard-
ware, the vlan pseudo interface does not itself insert or remove
the 802.1Q encapsulation header. Instead, the vlan_tag is passed
out of band from the packet data.
A physical interface that is associated with a bond pseudo device
cannot at the same time be associated with a vlan interface.
However, a physical interface can be associated with multiple
vlan interfaces at the same time, as long as each of the vlan_tag
values are unique.
-vlandev iface
If the driver is a vlan pseudo device, disassociate the physical
interface iface from it. This breaks the link between the vlan
interface and its parent, clears its vlan tag, flags and its link
address.
Ifconfig displays the current configuration for a network interface when
no optional parameters are supplied. If a protocol family is specified,
ifconfig will report only the details specific to that protocol family.
If the driver supports the media selection system, the supported media
list will be included in the output, regardless of whether the -m flag is
passed or not.
The -b option passed before the interface name will print the link aggre-
gation state for bond pseudo devices.
If -L flag is supplied, address lifetime is displayed for IPv6 addresses,
as time offset string.
Optionally, the -a flag may be used instead of an interface name. This
flag instructs ifconfig to display information about all interfaces in
the system. The -d flag limits this to interfaces that are down, and -u
limits this to interfaces that are up. When no arguments are given, -a
is implied.
The -l flag may be used to list all available interfaces on the system,
with no other additional information. Use of this flag is mutually
exclusive with all other flags and commands, except for -d (only list
interfaces that are down) and -u (only list interfaces that are up).
Only the super-user may modify the configuration of a network interface.
NOTES
The media selection system is relatively new and only some drivers sup-
port it (or have need for it).
ifconfig does not change the network settings permanently, it should be
used only in a test and debug context. The permanent network settings
can be modified using the Network Preferences pane. In addition on Mac
OS X Server the permanent network settings can be changed with the
networksetup(8) command. Otherwise public APIs in the SystemConfigura-
tion framework are currently the only supported way to access and control
the state of network settings.
DIAGNOSTICS
Messages indicating the specified interface does not exist, the requested
address is unknown, or the user is not privileged and tried to alter an
interface's configuration.
BUGS
IPv6 link-local addresses are required for several basic communication
between IPv6 node. If they are deleted by ifconfig manually, the kernel
might show very strange behavior. So, such manual deletions are strongly
discouraged.
SEE ALSO
netstat(1), netintro(4), rc(8), routed(8)
networksetup(8) on Mac OS X Server
HISTORY
The ifconfig command appeared in 4.2BSD.
BSD July 15, 2004 BSD
Mac OS X 10.5.2 - Generated Sun Mar 23 09:27:35 CDT 2008