IFCONFIG(8C)                                                      IFCONFIG(8C)


NAME
       ifconfig - configure network interface parameters

SYOPNSIS
       /etc/ifconfig  interface  address_family [ address [ dest_address ] ] [
       parameters ]
       /etc/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  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
                      interface.

       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,
                      encapsulate  outgoing  messages  in a manner which mini‐
                      mizes 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 encapsu‐
                      lations 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 encapsula‐
                      tion.

       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
                      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 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
                      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 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‐
       face.

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        May 22, 1986                     IFCONFIG(8C)
 
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