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BSD 2.11 - man page for ifconfig (bsd section 8)

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IFCONFIG(8)									      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 parameters.  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  interfaces,  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 interface is marked ``down'', the sys-
		      tem will not attempt to transmit messages through that interface.  If  pos-
		      sible,  the  interface  will  be	reset to disable reception as well.  This
		      action does not automatically disable routes using the interface.

       trailers       Request the use of a ``trailer''	link  level  encapsulation  when  sending
		      (default).  If a network interface supports trailers, the system 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);  cur-
		      rently,  only 10 Mb/s Ethernet), this flag indicates that the system should
		      request that other systems use trailers when sending to this  host.   Simi-
		      larly,  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 Protocol in mapping  between  net-
		      work level addresses and link level addresses (default).	This is currently
		      implemented for mapping between DARPA Internet addresses and 10Mb/s  Ether-
		      net 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 met-
		      ric 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.

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

       -debug	      Disable driver dependent debugging code.

       netmask mask   (Inet only) Specify how much of the address to reserve for subdividing net-
		      works 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 net-
		      work 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 net-
		      work.  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 network 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)

4.2 Berkeley Distribution		November 16, 1996			      IFCONFIG(8)
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