IFCONFIG(8)

NAME
ifconfig - configure network interface parameters

SYNOPSIS
ifconfig [-N] interface address_family [ address [dest_address]] [parameters]
ifconfig [-hLmNvz] interface [protocol_family]
ifconfig -a [-bdhLNmsuvz] [protocol_family]
ifconfig -l [-bdsu]
ifconfig -s interface
ifconfig -C

DESCRIPTION
ifconfig is used to assign an address to a network interface and/or configure 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.

Available operands for ifconfig:

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”. For the Xerox Network Systems(tm) family, addresses are net:a.b.c.d.e.f, where net is the assigned network number (in decimal), and each of the six bytes of the host number, a through f, are specified in hexadecimal. The host number may be omitted on Ethernet interfaces, which use the hardware physical address, and on interfaces other than the first. For the ISO family, addresses are specified as a long hexadecimal string, as in the Xerox family. However, two consecutive dots imply a zero byte, and the dots are optional, if the user wishes to (carefully) count out long strings of digits in network byte order.

address_family
    Specifies the address_family which affects interpretation of the remaining parameters. Since an interface can receive transmissions in differing protocols with different naming schemes, specifying the address family is recommended. The address or protocol families currently supported are “inet”, “inet6”, “atalk”, “iso”, and “link”.

interface
    The interface parameter is a string of the form “name unit”, for example, “en0”

The following parameters may be set with ifconfig:

active
    This keyword applies when ifconfig adds or modifies any link-layer address. It indicates that ifconfig should “activate” the address. Activation makes an address the default source for transmissions on the interface. You may not delete the active address from an interface. You must activate some other address, first.

advbase n
    If the driver is a carp(4) pseudo-device, set the base advertisement interval to n seconds. This ia an 8-bit number; the default value is 1 second.

advskew n
    If the driver is a carp(4) pseudo-device, skew the advertisement interval by n. This is an 8-bit number; the default value is 0.

    Taken together the advbase indicate how frequently, in seconds, the host will advertise the fact that it considers itself the master of the virtual host. The formula is advbase + (advskew / 256). If the master does not advertise within three times this interval, this host will begin advertising as master.

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.

-alias
    Remove the specified network address alias.

arp Enable the use of the Address Resolution Protocol in mapping between network level addresses and link level addresses (default). This is currently implemented for mapping between DARPA Internet addresses and Ethernet addresses.

-arp
    Disable the use of the Address Resolution Protocol.

anycast
    (inet6 only) Set the IPv6 anycast address bit.

-anycast
    (inet6 only) Clear the IPv6 anycast address bit.

broadcast mask
    (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.

carpdev iface
    If the driver is a carp(4) pseudo-device, attach it to iface. If not specified, the kernel will attempt to select an interface with a subnet matching that of the carp interface.

debug
    Enable driver dependent debugging code; usually, this turns on extra console error logging.

-debug
    Disable driver dependent debugging code.

delete
    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. delete does not work for IPv6 addresses. Use -alias with explicit IPv6 address instead.

dest_address
    Specify the address of the correspondent on the other end of a point to point link.

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.

ipdst
    This is used to specify an Internet host who is willing to receive ip packets encapsulating NS packets bound for a remote network. An apparent point to point link is constructed, and the address specified will be taken as the NS address and network of the destination. IP encapsulation of CLNP packets is done differently.

media type
    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” or “AUI” would change the currently active connector to the AUI port. Setting it to “10baseT” or “UTP” would activate twisted pair. Refer to the interfaces' driver specific man page for a complete list of the available types and the ifmedia(4) manual page for a list of media types. See the -m flag below.

mediaopt opts
    Set the specified media options on the interface. opts 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. Also see the ifmedia(4) manual page for a list of media options.

-mediaopt opts
    Disable the specified media options on the interface.

mode mode
    If the driver supports the media selection system, set the specified operating mode on the interface to mode. For IEEE 802.11 wireless interfaces that support multiple operating modes this directive is used to select between 802.11a (“11a”), 802.11b (“11b”), and 802.11g (“11g”) operating modes.

instance minst
    Set the media instance to minst. This is useful for devices which have multiple physical layer interfaces (PHYs). Setting the instance on such devices may not be strictly required by the network interface driver as the driver may take care of this automatically; see the driver's manual page for more information.

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. Most interfaces don't support this option.

netmask mask
    (inet, inet6, and ISO) Specify how much of the address to reserve for subdividing networks into sub-networks. 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.

    For INET and INET6 addresses, the netmask can also be given with slash-notation after the address (e.g 192.168.17.3/24).

nsellength n
    (ISO only) This specifies a trailing number of bytes for a received NSAP used for local identification, the remaining leading part of which is taken to be the NET (Network Entity Title). The default value is 1, which is conformant to US GOSIP. When an ISO address is set in an ifconfig command, it is really the NSAP which is being specified. For example, in US GOSIP, 20 hex digits should be specified in the ISO NSAP to be assigned to the interface. There is some evidence that a number different from 1 may be useful for AFI 37 type addresses.

state state
    Explicitly force the carp(4) pseudo-device to enter this state. Valid states are init, backup, and master.

frag threshold
    (IEEE 802.11 devices only) Configure the fragmentation threshold for IEEE 802.11-based wireless network interfaces.

rts threshold
    (IEEE 802.11 devices only) Configure the RTS/CTS threshold for IEEE 802.11-based wireless network interfaces. This controls the number of bytes used for the RTS/CTS handshake boundary. The threshold can be any value between 0 and 2347. The default is 2347, which indicates the RTS/CTS mechanism should not be used.

ssid id
    (IEEE 802.11 devices only) Configure the Service Set Identifier (a.k.a. the network name) for IEEE 802.11-based wireless network interfaces. The id can either be any text string up to 32 characters in length, or a series of up to 64 hexadecimal digits preceded by “0x”. Setting id to the empty string allows the interface to connect to any available access point.

nwid id
    Synonym for “ssid”.

hidessid
    (IEEE 802.11 devices only) When operating as an access point, do not broadcast the SSID in beacon frames or respond to probe request frames unless they are directed to the ap (i.e., they include the ap's SSID). By default, the SSID is included in beacon frames and undirected probe request frames are answered.

-hidessid
    (IEEE 802.11 devices only) When operating as an access point, broadcast the SSID in beacon frames and answer and respond to undirected probe request frames (default).

nwkey key
    (IEEE 802.11 devices only) Enable WEP encryption for IEEE 802.11-based wireless network interfaces with the key. The key can either be a string, a series of hexadecimal digits preceded by “0x”, or a set of keys in the form n:k1,k2,k3,k4, where n specifies which of keys will be used for all transmitted packets, and four keys, k1 through k4, are configured as WEP keys. Note that the order must be match within same network if multiple keys are used. For IEEE 802.11 wireless network, the length of each key is restricted to 40 bits, i.e. 5-character string or 10 hexadecimal digits, while the WaveLAN/IEEE Gold cards accept the 104 bits (13 characters) key.

nwkey persist
    (IEEE 802.11 devices only) Enable WEP encryption for IEEE 802.11-based wireless network interfaces with the persistent key written in the network card.

nwkey persist:key
    (IEEE 802.11 devices only) Write the key to the persistent memory of the network card, and enable WEP encryption for IEEE 802.11-based wireless network interfaces with the key.

-nwkey
    (IEEE 802.11 devices only) Disable WEP encryption for IEEE 802.11-based wireless network interfaces.

apbridge
    (IEEE 802.11 devices only) When operating as an access point, pass packets between wireless clients directly (default).

-apbridge
    (IEEE 802.11 devices only) When operating as an access point, pass packets through the system so that they can be forwared using some other mechanism. Disabling the internal bridging is useful when traffic is to be processed with packet filtering.

pass passphrase
    If the driver is a carp(4) pseudo-device, set the authentication key to passphrase. There is no passphrase by default

powersave
    (IEEE 802.11 devices only) Enable 802.11 power saving mode.

-powersave
    (IEEE 802.11 devices only) Disable 802.11 power saving mode.

powersavesleep duration
    (IEEE 802.11 devices only) Set the receiver sleep duration in milliseconds for 802.11 power saving mode.

bssid bssid
    (IEEE 802.11 devices only) Set the desired BSSID for IEEE 802.11-based wireless network interfaces.

-bssid
    (IEEE 802.11 devices only) Unset the desired BSSID for IEEE 802.11-based wireless network interfaces. The interface will automatically select a BSSID in this mode, which is the default.

chan chan
    (IEEE 802.11 devices only) Select the channel (radio frequency) to be used for IEEE 802.11-based wireless network interfaces.

-chan
    (IEEE 802.11 devices only) Unset the desired channel to be used for IEEE 802.11-based wireless network interfaces. It doesn't affect the channel to be created for IBSS or hostap mode.

list scan
    (IEEE 802.11 devices only) Display the access points and/or ad-hoc neighbors located in the vicinity. The -v flag may be used to display long SSIDs. -v also causes received information elements to be displayed symbolically. Only the super-user can use this command.

tunnel src_addr[,src_port]
    dest_addr[,dest_port] (IP tunnel devices only) Configure the physical source and destination address for IP tunnel interfaces, including gif(4). The arguments src_addr and dest_addr are interpreted as the outer source/destination for the encapsulating IPv4/IPv6 header.

    On a gre(4) interface in UDP mode, the arguments src_port and dest_port are interpreted as the outer source/destination port for the encapsulating UDP header.

deletetunnel
    Unconfigure the physical source and destination address for IP tunnel interfaces previously configured with tunnel.

create
    Create the specified network pseudo-device.

destroy
    Destroy the specified network pseudo-device.

pltime n
    (inet6 only) Set preferred lifetime for the address.

prefixlen n
    (inet and inet6 only) Effect is similar to netmask. but you can specify by prefix length by digits.

deprecated
    (inet6 only) Set the IPv6 deprecated address bit.

-deprecated
    (inet6 only) Clear the IPv6 deprecated address bit.

tentative
    (inet6 only) Set the IPv6 tentative address bit.

-tentative
    (inet6 only) Clear the IPv6 tentative address bit.

eui64
    (inet6 only) Fill interface index (lowermost 64bit of an IPv6 address) automatically.

link[0-2]
    Enable special processing of the link level of the interface. These three options are interface 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.

linkstr
    Set a link-level string parameter for the interface. This functionality varies from interface to interface. Refer to the man page for the specific driver for more information.

-linkstr
    Remove an interface link-level string parameter.

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.

vhid n
    If the driver is a carp(4) pseudo-device, set the virtual host ID to n. Acceptable values are 1 to 255.

vlan vid
    If the interface is a vlan(4) pseudo-interface, set the VLAN identifier to vid. These are the first 12 bits (0-4095) from a 16-bit integer used to create an 802.1Q VLAN header for packets sent from the vlan(4) interface. Note that vlan and vlanif must be set at the same time.

vlanif iface
    If the interface is a vlan(4) pseudo-interface, associate the physical interface iface with it. Packets transmitted through the vlan(4) interface will be diverted to the specified physical interface iface with 802.1Q VLAN encapsulation. Packets with 802.1Q encapsulation received by the physical interface with the correct VLAN tag will be diverted to the associated vlan(4) pseudo-interface. The VLAN interface is assigned a copy of the physical interface's flags and Ethernet address. If the vlan(4) interface already has a physical interface associated with it, this command will fail. To change the association to another physical interface, the existing association must be cleared first. Note that vlanif and vlan must be set at the same time.

agrport iface
    Add iface to the agr(4) interface.

-agrport iface
    Remove iface from the agr(4) interface.

vltime n
    (inet6 only) Set valid lifetime for the address.

ip4csum
    Shorthand of “ip4csum-tx ip4csum-rx”

-ip4csum
    Shorthand of “-ip4csum-tx -ip4csum-rx”

tcp4csum
    Shorthand of “tcp4csum-tx tcp4csum-rx”

-tcp4csum
    Shorthand of “-tcp4csum-tx -tcp4csum-rx”

udp4csum
    Shorthand of “udp4csum-tx udp4csum-rx”

-udp4csum
    Shorthand of “-udp4csum-tx -udp4csum-rx”

tcp6csum
    Shorthand of “tcp6csum-tx tcp6csum-rx”

-tcp6csum
    Shorthand of “-tcp6csum-tx -tcp6csum-rx”

udp6csum
    Shorthand of “udp6csum-tx udp6csum-rx”

-udp6csum
    Shorthand of “-udp6csum-tx -udp6csum-rx”

ip4csum-tx
    Enable hardware-assisted IPv4 header checksums for the out-bound direction.

-ip4csum-tx
    Disable hardware-assisted IPv4 header checksums for the out-bound direction.

ip4csum-rx
    Enable hardware-assisted IPv4 header checksums for the in-bound direction.

-ip4csum-rx
    Disable hardware-assisted IPv4 header checksums for the in-bound direction.

tcp4csum-tx
    Enable hardware-assisted TCP/IPv4 checksums for the out-bound direction.

-tcp4csum-tx
    Disable hardware-assisted TCP/IPv4 checksums for the out-bound direction.

tcp4csum-rx
    Enable hardware-assisted TCP/IPv4 checksums for the in-bound direction.

-tcp4csum-rx
    Disable hardware-assisted TCP/IPv4 checksums for the in-bound direction.

udp4csum-tx
    Enable hardware-assisted UDP/IPv4 checksums for the out-bound direction.

-udp4csum-tx
    Disable hardware-assisted UDP/IPv4 checksums for the out-bound direction.

udp4csum-rx
    Enable hardware-assisted UDP/IPv4 checksums for the in-bound direction.

-udp4csum-rx
    Disable hardware-assisted UDP/IPv4 checksums for the in-bound direction.

tcp6csum-tx
    Enable hardware-assisted TCP/IPv6 checksums for the out-bound direction.

-tcp6csum-tx
    Disable hardware-assisted TCP/IPv6 checksums for the out-bound direction.

tcp6csum-rx
    Enable hardware-assisted TCP/IPv6 checksums for the in-bound direction.

-tcp6csum-rx
    Disable hardware-assisted TCP/IPv6 checksums for the in-bound direction.

udp6csum-tx
    Enable hardware-assisted UDP/IPv6 checksums for the out-bound direction.

-udp6csum-tx
    Disable hardware-assisted UDP/IPv6 checksums for the out-bound direction.

udp6csum-rx
    Enable hardware-assisted UDP/IPv6 checksums for the in-bound direction.

-udp6csum-rx
    Disable hardware-assisted UDP/IPv6 checksums for the in-bound direction.

tso4
    Enable hardware-assisted TCP/IPv4 segmentation on interfaces that support it.

-tso4
    Disable hardware-assisted TCP/IPv4 segmentation on interfaces that support it.

tso6
    Enable hardware-assisted TCP/IPv6 segmentation on interfaces that support it.

-tso6
    Disable hardware-assisted TCP/IPv6 segmentation on interfaces that support it.

maxupd n
    If the driver is a pfsync(4) pseudo-device, indicate the maximum number of updates for a single state which can be collapsed into one. This is an 8-bit number; the default value is 128.

syncdev iface
    If the driver is a pfsync(4) pseudo-device, use the specified interface to send and receive pfsync state synchronisation messages.

-syncdev
    If the driver is a pfsync(4) pseudo-device, stop sending pfsync state synchronisation messages over the network.

syncpeer peer_address
    If the driver is a pfsync(4) pseudo-device, make the pfsync link point-to-point rather than using multicast to broadcast the state synchronisation messages. The peer_address is the IP address of the other host taking part in the pfsync cluster. With this option, pfsync(4) traffic can be protected using ipsec(4).

-syncpeer
    If the driver is a pfsync(4) pseudo-device, broadcast the packets using multicast.

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 -s flag is passed before an interface name, ifconfig will attempt to query the interface for its media status. If the interface supports reporting media status, and it reports that it does not appear to be connected to a network, ifconfig will exit with status of 1 (false); otherwise, it will exit with a zero (true) exit status. Not all interface drivers support media status reporting.

If the -m flag is passed before an interface name, ifconfig will display all of the supported media for the specified interface. If the -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. This is also the default behaviour when no arguments are given to ifconfig on the command line. When -a is used, the output can be modified by adding more flags: -d limits this to interfaces that are down, -u limits this to interfaces that are up, -b limits this to broadcast interfaces, and -s omits interfaces which appear not to be connected to a network.

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), -u (only list interfaces that are up), -s (only list interfaces that may be connected), -b (only list broadcast interfaces).

The -C flag may be used to list all of the interface cloners available on the system, with no additional information. Use of this flag is mutually exclusive with all other flags and commands.

The -v flag prints statistics on packets sent and received on the given interface. If -h is used in conjunction with -v, the byte statistics will be printed in "human-readable" format. The -z flag is identical to the -v flag except that it zeros the interface input and output statistics after printing them.

The -N flag is just the opposite of the -n flag in netstat(1) or in route(8): it tells ifconfig to try to resolve numbers to hostnames or to service names. The default ifconfig behavior is to print numbers instead of names.

Only the super-user may modify the configuration of a network interface.

EXAMPLES
Add a link-layer (MAC) address to an Ethernet:

ifconfig sip0 link 00:11:22:33:44:55

Add and activate a link-layer (MAC) address:

ifconfig sip0 link 00:11:22:33:44:55 active

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.

SEE ALSO
netstat(1), agr(4), carp(4), ifmedia(4), netintro(4), pfsync(4), vlan(4), ifconfig.if(5), rc(8), routed(8)

HISTORY
The ifconfig command appeared in 4.2BSD.