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       ifconfig	- configure network interface parameters

       /etc/ifconfig  interface	 address_family	[ address [ dest_address ] ] [
       parameters ]
       /etc/ifconfig interface [ protocol_family ]

       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  ma-
       chine;  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  ad-
       dress expressed in the Internet standard	``dot notation''.  For the Xe-
       rox 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 auto-
		      matically	when setting the first address	on  an	inter-
		      face.  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  system will not attempt to transmit mes-
		      sages through that interface.  If	possible,  the	inter-
		      face  will  be reset to disable reception	as well.  This
		      action does not automatically disable routes  using  the

       trailers	      Request  the  use	of a ``trailer'' link level encapsula-
		      tion when	sending	(default).   If	 a  network  interface
		      supports	trailers,  the system will, when possible, en-
		      capsulate	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 re-
		      quests.  Currently used by Internet protocols only.

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

       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 10Mb/s Eth-
		      ernet 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(8c)).   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 console error logging.

       -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 hexadec-
		      imal  number  with a leading 0x, with a dot-notation In-
		      ternet 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.

       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  ad-
		      dress 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	 pack-
		      ets bound	for a remote network.  In this case, an	appar-
		      ent 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  pro-
       tocol family.

       Only  the  super-user  may modify the configuration of a	network	inter-

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

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

4.2 Berkeley Distribution	 May 22, 1986			  IFCONFIG(8C)


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