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 configure network interface parame-ters. parameters.
ters. 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 transmissions in differing protocols with different naming schemes, spec-ifying specifying
ifying the address family is recommended. The address or protocol 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 example, ``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 compatibility 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 (Ethernet, 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 bond-mode bondmode
mode below). In this mode, the device conforms to the IEEE 802.3ad Link Aggregation specifica-tion. specification.
tion.
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 physical 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 having its ethernet address re-pro-grammed, re-programmed,
grammed, 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 use-able useable
able 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 conditions 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 eth-ernet ethernet
ernet interfaces may be associated with a bond.
-bonddev iface
If the interface is a bond pseudo device, disassociate the physical 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 dis-able disable
able 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 hardware 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 mutually exclusive use of one of several different physical media
connectors. For example, a 10Mb/s Ethernet interface might support 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 specified 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 destination address for IP tunnel
interfaces (gif(4)). The arguments 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 compatibility.
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 inter-faces interfaces
faces support setting the MTU, and some interfaces have range restrictions.
netmask mask
(Inet only.) Specify how much of the address to reserve for subdividing networks into sub-net-works. sub-networks.
works. The mask includes the network part of the local address and the subnet part, which is
taken from the host field of the address. The mask can be specified 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 parameter is omitted, 64 is used.
remove Another name for the -alias parameter. Introduced for compatibility with BSD/OS.
link[0-2]
Enable special processing of the link level of the interface. These three options are inter-face interface
face specific in actual effect, however, they are in general used to select special modes of
operation. 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 interface 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-initialized.
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 com-mand command
mand will fail. To change the association to another physical interface, the existing associa-tion association
tion must be cleared first using -vlandev.
If the physical interface supports 802.1Q VLAN tagging in hardware, 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 multi-ple multiple
ple 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 aggregation 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 dis-play display
play 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 infor-mation. information.
mation. 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 support 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 addi-tion addition
tion on Mac OS X Server the permanent network settings can be changed with the networksetup(8) command.
Otherwise public APIs in the SystemConfiguration 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
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