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 ifconfig(1M)							ifconfig(1M)




 NAME
      ifconfig - configure network interface parameters

 SYNOPSIS
      ifconfig interface address_family [address [dest_address]] [parameters]

      ifconfig interface [address_family]

 DESCRIPTION
      The first form of the ifconfig command assigns an address to a network
      interface and/or configures network interface parameters.	 ifconfig
      must be used at boot time to define the network address of each
      interface present on a machine.  It can also be used at other times to
      redefine an interface's address or other operating parameters.

      The second form of the command, without address_family, displays the
      current configuration for interface.  If address_family is also
      specified, ifconfig reports only the details specific to that address
      family.

      Only a user with appropriate privileges can modify the configuration
      of a network interface.  All users can run the second form of the
      command.

    Arguments
      ifconfig recognizes the following arguments:

	   address	   Either a host name present in the host name
			   database (see hosts(4)), or a DARPA Internet
			   address expressed in Internet standard dot
			   notation (see inet(3N)).

	   address_family  Name of protocol on which naming scheme is based.
			   An interface can receive transmissions in
			   differing protocols, each of which may require
			   separate naming schemes.  Therefore, it is
			   necessary to specify the address_family, which
			   may affect interpretation of the remaining
			   parameters on the command line.  The only address
			   family currently supported is inet (DARPA-
			   Internet family).

	   dest_address	   Address of destination system.  Consists of
			   either a host name present in the host name
			   database (see hosts(4)), or a DARPA Internet
			   address expressed in Internet standard dot
			   notation (see inet(3N)).

	   interface	   A string of the form nameunit, such as lan0.
			   (See the Interface Naming subsection given
			   below.)



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 ifconfig(1M)							ifconfig(1M)




	   parameters	   One or more of the following operating
			   parameters:

			   up		  Mark an interface "up".  Enables
					  interface after an ifconfig down.
					  Occurs automatically when setting
					  the address on an interface.
					  Setting this flag has no effect if
					  the hardware is "down".

			   down		  Mark an interface "down".  When an
					  interface is marked "down", the
					  system will not attempt to
					  transmit messages through that
					  interface.

			   broadcast	  (Inet only) Specify the address
					  that represents broadcasts to the
					  network.  The default broadcast
					  address is the address with a host
					  part of all 1's.

			   metric n	  Set the routing metric of the
					  interface to n.  The default is 0.
					  The routing metric is used by the
					  routing protocol (see gated(1M)).
					  Higher metrics have the effect of
					  making a route less favorable;
					  metrics are counted as additional
					  hops to the destination network or
					  host.

			   netmask mask	  (Inet only) Specify how much of
					  the address to reserve for
					  subdividing networks into sub-
					  networks or aggregating networks
					  into supernets.  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 (see
					  networks(4)).	 For subdividing
					  networks into sub-networks, mask
					  must include the network part of
					  the local address, and the subnet
					  part which is taken from the host
					  field of the address.	 mask must
					  contain 1's in the bit positions
					  in the 32-bit address that are to
					  be used for the network and subnet



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 ifconfig(1M)							ifconfig(1M)




					  parts, and 0's in the host part.
					  The 1's in the mask must be
					  contiguous starting from the
					  leftmost bit position in the 32-
					  bit field.  mask must contain at
					  least the standard network
					  portion, and the subnet field must
					  be contiguous with the network
					  portion.  The subnet field must
					  contain at least 1 bit. For
					  aggregating networks into
					  supernets, mask must only include
					  a portion of the network part.
					  mask must contain contiguous 1's
					  in the bit positions starting from
					  the leftmost bit of the 32-bit
					  field.

			   arp		  Enable the user of the Address
					  Resolution Protocol in mapping
					  between network level addresses
					  and link level addresses
					  (default).  If an interface
					  already had the Address Resolution
					  Protocol disabled, the user must
					  "unplumb" the interface before it
					  can be enabled for Address
					  Resolution Protocol.

			   -arp		  Disable the use of the Address
					  Resolution Protocol.	If an
					  interface already had the Address
					  Resolution Protocol enabled, the
					  user must "unplumb" the interface
					  before it can be disabled for
					  Address Resolution Protocol.

			   plumb	  Setup the Streams plumbing needed
					  for TCP/IP for a primary interface
					  name.	 (See the Interface Naming
					  subsection given below.). By
					  default, the plumb operation is
					  done automatically when an IP
					  address is specified for an
					  interface.

			   unplumb	  Tear down the Streams plumbing for
					  a primary interface name.  (See
					  the Interface Naming subsection
					  given below.) Secondary interface
					  does not require "plumbing" and it



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 ifconfig(1M)							ifconfig(1M)




					  can be removed by assigning an IP
					  address of 0.0.0.0.

    Interface Naming
      The interface name associated with a network card is composed of the
      name of the interface (e.g.  lan or snap ), the ppa number which
      identifies the card instance for this interface, and an optional IP
      index number which allows the configuration of multiple IP addresses
      for an interface.	 For LAN cards, the interface name lan will be used
      to designate Ethernet encapsulation and snap for IEEE 802.3
      encapsulation.  The lanscan command can be used to display the
      interface name and ppa number of each interface that is associated
      with a network card (see lanscan(1M)).

      Multiple IP addresses assigned to the same interface may be in
      different subnets.  An example of an interface name without an IP
      index number is lan0.  An example of an interface name with a IP index
      number is lan0:1.	 Note: specifying lan0:0 is equivalent to lan0.

    Loopback Interface
      The loopback interface (lo0) is automatically configured when the
      system boots with the TCP/IP software. The default IP address and
      netmask of the loopback interface are 127.0.0.1 and 255.0.0.0,
      respectively.  The user is not permitted to change the address of the
      primary loopback interface (lo0:0).  It is permissible to assign other
      IP addresses to lo0 with non-zero IP index numbers (lo0:1, lo0:2,
      etc).  This allows a system to have a "system IP" address that is
      available as long as one interface remains usable.

    Supernets
      A supernet is a collection of smaller networks.  Supernetting is a
      technique of using the netmask to aggregate a collection of smaller
      networks into a supernet.

      This technique is particularly useful when the limit of 254 hosts per
      class C network is too restrictive. In those situations a netmask
      containing only a portion of the network part may be applied to the
      hosts in these networks to form a supernet.  This supernet netmask
      should be applied to those interfaces that connect to the supernet
      using the ifconfig command.  For example, a host can configure its
      interface to connect to a class C supernet, 192.6, by configuring an
      IP address of 192.6.1.1 and a netmask of 255.255.0.0 to its interface.

 DIAGNOSTICS
      Messages indicate if 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.

 AUTHOR
      ifconfig was developed by HP and the University of California,
      Berkeley.



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 ifconfig(1M)							ifconfig(1M)




 SEE ALSO
      netstat(1), lanscan(1M), hosts(4), routing(7).




















































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