IFCONFIG(8)	    UNIX Programmer's Manual	      IFCONFIG(8)


NAME
     ifconfig - configure network interface parameters

SYOPNSIS
     /sbin/ifconfig interface address_family [ address [
     dest_address ] ] [ parameters ]
     /sbin/ifconfig interface [ protocol_family ]

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.  The interface parameter is a string
     of the form ``name unit'', e.g. ``en0''.

     Since an interface may receive transmissions in differing
     protocols, each of which may require separate naming
     schemes, it is necessary to specify the address_family,
     which may change the interpretation of the remaining parame-
     ters.  The address families currently supported are ``inet''
     and ``ns''.

     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 10Mb/s Ethernet inter-
     faces, which use the hardware physical address, and on
     interfaces other than the first.

     The following parameters may be set with ifconfig:

     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.

     down	    Mark an interface ``down''.  When an inter-
		    face 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.


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IFCONFIG(8)	    UNIX Programmer's Manual	      IFCONFIG(8)


     trailers	    Request the use of a ``trailer'' link level
		    encapsulation when sending (default).  If a
		    network interface supports trailers, the sys-
		    tem will, when possible, encapsulate outgoing
		    messages in a manner which minimizes the
		    number of memory to memory copy operations
		    performed by the receiver.	On networks that
		    support the Address Resolution Protocol (see
		    arp(4P); currently, only 10 Mb/s Ethernet),
		    this flag indicates that the system should
		    request that other systems use trailers when
		    sending to this host.  Similarly, trailer
		    encapsulations will be sent to other hosts
		    that have made such requests.  Currently used
		    by Internet protocols only.

     -trailers	    Disable the use of a ``trailer'' link level
		    encapsulation.

     arp	    Enable the use of the Address Resolution Pro-
		    tocol in mapping between network level
		    addresses and link level addresses (default).
		    This is currently implemented for mapping
		    between DARPA Internet addresses and 10Mb/s
		    Ethernet addresses.

     -arp	    Disable the use of the Address Resolution
		    Protocol.

     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 favor-
		    able; metrics are counted as addition hops to
		    the destination network or host.

     debug	    Enable driver dependent debugging code; usu-
		    ally, this turns on extra console error log-
		    ging.

     -debug	    Disable driver dependent debugging code.

     netmask mask   (Inet only) 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


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IFCONFIG(8)	    UNIX Programmer's Manual	      IFCONFIG(8)


		    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 con-
		    tiguous with the network portion.

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

     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.

     ipdst	    (NS only) This is used to specify an Internet
		    host who is willing to receive ip packets
		    encapsulating NS packets bound for a remote
		    network.  In this case, an apparent point to
		    point link is constructed, and the address
		    specified will be taken as the NS address and
		    network of the destinee.

     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.

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

DIAGNOSTICS
     Messages indicating the specified interface does not exit,
     the requested address is unknown, or the user is not
     privileged and tried to alter an interface's configuration.

SEE ALSO
     netstat(1), intro(4N), rc(8)


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