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



[1mNAME
     [0mifconfig - configure network interface parameters

[1mSYNOPSIS
     /etc/ifconfig [0minterface address_family [ _a_d_d_r_e_s_s [
     _d_e_s_t__a_d_d_r_e_s_s ] ] [ _p_a_r_a_m_e_t_e_r_s ]
     [1m/etc/ifconfig [0minterface [ protocol_family ]

[1mDESCRIPTION
     [0m_I_f_c_o_n_f_i_g is used to assign an address to a network interface
     and/or configure network interface parameters.  _I_f_c_o_n_f_i_g
     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 _i_n_t_e_r_f_a_c_e 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 _a_d_d_r_e_s_s__f_a_m_i_l_y,
     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, _h_o_s_t_s(5), or a
     DARPA Internet address expressed in the Internet standard
     ``dot notation''.	For the Xerox Network Systems(tm) family,
     addresses are _n_e_t:_a._b._c._d._e._f, where _n_e_t 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 _i_f_c_o_n_f_i_g:

     [1mup             [0mMark 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.

     [1mdown	    [0mMark 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(8C)	    UNIX Programmer's Manual	     IFCONFIG(8C)



     [1mtrailers	    [0mRequest the use of a ``trailer'' link level
		    encapsulation when sending (default).  If a
		    network interface supports _t_r_a_i_l_e_r_s, 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
		    _a_r_p(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.

     [1m-trailers	    [0mDisable the use of a ``trailer'' link level
		    encapsulation.

     [1marp	    [0mEnable 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.

     [1m-arp	    [0mDisable the use of the Address Resolution
		    Protocol.

     [1mmetric [0m_n	    Set the routing metric of the interface to _n,
		    default 0.	The routing metric is used by the
		    routing protocol (_r_o_u_t_e_d(8c)).  Higher
		    metrics have the effect of making a route
		    less favorable; metrics are counted as addi-
		    tion hops to the destination network or host.

     [1mdebug	    [0mEnable driver dependent debugging code; usu-
		    ally, this turns on extra console error log-
		    ging.

     [1m-debug	    [0mDisable driver dependent debugging code.

     [1mnetmask [0m_m_a_s_k   (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 _n_e_t_w_o_r_k_s(5).	The mask contains 1's for



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



		    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.

     [1mdstaddr	    [0mSpecify the address of the correspondent on
		    the other end of a point to point link.

     [1mbroadcast	    [0m(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.

     [1mipdst	    [0m(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.

     _I_f_c_o_n_f_i_g 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.

[1mDIAGNOSTICS
     [0mMessages 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.

[1mSEE ALSO
     [0mnetstat(1), intro(4N), rc(8)

















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