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IFCONFIG(8)             FreeBSD System Manager's Manual            IFCONFIG(8)

     ifconfig -- configure network interface parameters

     ifconfig [-L] [-m] interface [create] [address_family] [address
              [dest_address]] [parameters]
     ifconfig interface destroy
     ifconfig -a [-L] [-d] [-m] [-u] [address_family]
     ifconfig -l [-d] [-u] [address_family]
     ifconfig [-L] [-d] [-m] [-u] [-C]

     The ifconfig utility is used to assign an address to a network interface
     and/or configure network interface parameters.  The ifconfig utility 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:

             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

             For ``inet6'' family, it is also possible to specify the prefix
             length using the slash notation, like ::1/128.  See the prefixlen
             parameter below for more information.

             The link-level (``link'') address is specified as a series of
             colon-separated hex digits.  This can be used to e.g. set a new
             MAC address on an ethernet interface, though the mechanism used
             is not ethernet-specific.  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.

             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'',
             ``atalk'', ``ipx'', and ``link''.  The default is ``inet''.
             ``ether'' and ``lladdr'' are synonyms for ``link''.

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

             This parameter is a string of the form ``name unit'', for exam-
             ple, ``ed0''.

     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 non-conflicting netmask must be given.  Usually
             0xffffffff is most appropriate.

     -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.

             (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)).

             If the Address Resolution Protocol is enabled, the host will only
             reply to requests for its addresses, and will never send any

             If the Address Resolution Protocol is enabled, the host will per-
             form normally, sending out requests and listening for replies.

             (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.

             Put interface into permanently promiscuous mode.

             Disable permanently promiscuous mode.

     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.

     eui64   (Inet6 only.)  Fill interface index (lowermost 64bit of an IPv6
             address) automatically.

     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.

             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 the specified network pseudo-device.

     plumb   Another name for the create parameter.  Included for Solaris com-

             Another name for the destroy parameter.  Included for Solaris

     vlan vlan_tag
             If the interface is a vlan(4) pseudo interface, set the VLAN tag
             value to vlan_tag.  This value is a 16-bit number which is used
             to create an 802.1Q VLAN header for packets sent from the vlan(4)
             interface.  Note that vlan and vlandev must both be set at the
             same time.

     vlandev iface
             If the interface is a vlan(4) pseudo device, associate 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 encap-
             sulation received by the parent interface with the correct VLAN
             tag will be diverted to the associated vlan(4) pseudo-interface.
             The vlan(4) interface is assigned a copy of the parent inter-
             face's flags and the parent's ethernet address.  The vlandev and
             vlan must both be set at the same time.  If the vlan(4) 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.

             Note: if the link0 flag is set on the vlan(4) interface, the
             vlan(4) pseudo interface's behavior changes: the link0 tells the
             vlan(4) interface that the parent interface supports insertion
             and extraction of VLAN tags on its own (usually in firmware) and
             that it should pass packets to and from the parent unaltered.

     -vlandev iface
             If the driver is a vlan(4) pseudo device, disassociate the physi-
             cal interface iface from it.  This breaks the link between the
             vlan(4) interface and its parent, clears its VLAN tag, flags and
             its link address and shuts the interface down.

     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-

     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.

             The prefix can also be specified using the slash notation after
             the address.  See the address option above for more information.

     range netrange
             Under appletalk, set the interface to respond to a netrange of
             the form startnet-endnet.  Appletalk uses this scheme instead of
             netmasks though FreeBSD implements it internally as a set of net-

     remove  Another name for the -alias parameter.  Introduced for compati-
             bility with BSD/OS.

     phase   The argument following this specifies the version (phase) of the
             Appletalk network attached to the interface.  Values of 1 or 2
             are permitted.

             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.

             Disable special processing at the link level with the specified

     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-

     ssid ssid
             For IEEE 802.11 wireless interfaces, set the desired Service Set
             Identifier (aka network name).  The SSID is a string up to 32
             characters in length and may be specified as either a normal
             string or in hexadecimal when proceeded by `0x'.  Additionally,
             the SSID may be cleared by setting it to `-'.

     nwid ssid
             Another name for the ssid parameter.  Included for NetBSD compat-

     stationname name
             For IEEE 802.11 wireless interfaces, set the name of this sta-
             tion.  It appears that the station name is not really part of the
             IEEE 802.11 protocol though all interfaces seem to support it.
             As such it only seems to be meaningful to identical or virtually
             identical equipment.  Setting the station name is identical in
             syntax to setting the SSID.

     station name
             Another name for the stationname parameter.  Included for BSD/OS

     channel number
             For IEEE 802.11 wireless interfaces, set the desired channel.
             Channels range from 1 to 14, but the exact selection available
             depends on the region your adaptor was manufactured for.  Setting
             the channel to 0 will give you the default for your adaptor.
             Many adaptors ignore this setting unless you are in ad-hoc mode.

     authmode mode
             For IEEE 802.11 wireless interfaces, set the desired authentica-
             tion mode in infrastructure mode.  Not all adaptors support all
             modes.  The set of valid modes is ``none'', ``open'', and
             ``shared''.  Modes are case insensitive.

             For IEEE 802.11 wireless interfaces, enable powersave mode.

             For IEEE 802.11 wireless interfaces, disable powersave mode.

     powersavesleep sleep
             For IEEE 802.11 wireless interfaces, set the desired max power-
             save sleep time in milliseconds.

     wepmode mode
             For IEEE 802.11 wireless interfaces, set the desired WEP mode.
             Not all adaptors support all modes.  The set of valid modes is
             ``off'', ``on'', and ``mixed''.  ``Mixed'' mode explicitly tells
             the adaptor to allow association with access points which allow
             both encrypted and unencrypted traffic.  On these adaptors,
             ``on'' means that the access point must only allow encrypted con-
             nections.  On other adaptors, ``on'' is generally another name
             for ``mixed''.  Modes are case insensitive.

     weptxkey index
             For IEEE 802.11 wireless interfaces, set the WEP key to be used
             for transmission.

     wepkey key|index:key
             For IEEE 802.11 wireless interfaces, set the selected WEP key.
             If an index is not given, key 1 is set.  A WEP key will be either
             5 or 13 characters (40 or 104 bits) depending of the local net-
             work and the capabilities of the adaptor.  It may be specified
             either as a plain string or as a string of hexadecimal digits
             proceeded by `0x'.  For maximum portability, hex keys are recom-
             mended; the mapping of text keys to WEP encryption is usually
             driver-specific.  In particular, the Windows drivers do this map-
             ping differently to FreeBSD.  A key may be cleared by setting it
             to `-'.  If WEP is supported then there are at least four keys.
             Some adaptors support more than four keys.  If that is the case,
             then the first four keys (1-4) will be the standard temporary
             keys and any others will be adaptor specific keys such as perma-
             nent keys stored in NVRAM.

     wep     Another way of saying wepmode on.  Included for BSD/OS compati-

     -wep    Another way of saying wepmode off.  Included for BSD/OS compati-

     nwkey key
             Another way of saying:

             ``wepmode on weptxkey 1 wepkey 1:key wepkey 2:- wepkey 3:- wepkey

             Included for NetBSD compatibility.

     nwkey n:k1,k2,k3,k4
             Another way of saying

             ``wepmode on weptxkey n wepkey 1:k1 wepkey 2:k2 wepkey 3:k3
             wepkey 4:k4''.

             Included for NetBSD compatibility.

     -nwkey  Another way of saying wepmode off.

             Included for NetBSD compatibility.

     The ifconfig utility 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 pro-
     tocol family.

     If the driver does supports the media selection system, the supported
     media list will be included in the output.

     If the -m flag is passed before an interface name, ifconfig will display
     all of the supported media for the specified interface.  If -L flag is
     supplied, address lifetime is displayed for IPv6 addresses, as time off-
     set 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).

     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.

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

     The media selection system is relatively new and only some drivers sup-
     port it (or have need for it).

     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.

     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

     netstat(1), netintro(4), vlan(4), rc(8), routed(8)

     The ifconfig utility appeared in 4.2BSD.

FreeBSD 4.10                     July 2, 2001                     FreeBSD 4.10


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