IFCONFIG(8)		   Linux Programmer's Manual		   IFCONFIG(8)



NAME
       ifconfig - configure a network interface


SYNOPSIS
       ifconfig [interface]
       ifconfig interface [aftype] options | address ...


NOTE
       This  program  is obsolete!  For replacement check ip addr and ip link.
       For statistics use ip -s link.


DESCRIPTION
       Ifconfig is used to configure the kernel-resident  network  interfaces.
       It is used at boot time to set up interfaces as necessary.  After that,
       it is usually only needed when  debugging  or  when  system  tuning  is
       needed.

       If  no  arguments  are  given, ifconfig displays the status of the cur-
       rently active interfaces.  If a single interface argument is given,  it
       displays	 the  status of the given interface only; if a single -a argu-
       ment is given, it displays the status of	 all  interfaces,  even	 those
       that are down.  Otherwise, it configures an interface.


Address Families
       If  the	first  argument	 after the interface name is recognized as the
       name of a supported address family, that address	 family	 is  used  for
       decoding	 and  displaying  all protocol addresses.  Currently supported
       address families include inet (TCP/IP,  default),  inet6	 (IPv6),  ax25
       (AMPR  Packet  Radio),  ddp  (Appletalk	Phase 2), ipx (Novell IPX) and
       netrom (AMPR Packet radio).  All numbers supplied as parts in IPv4 dot-
       ted  decimal  notation may be decimal, octal, or hexadecimal, as speci-
       fied in the ISO C standard (that is, a leading 0x or 0X	implies	 hexa-
       decimal;	 otherwise, a leading '0' implies octal; otherwise, the number
       is interpreted as decimal). Use of hexamedial and octal numbers is  not
       RFC-compliant and therefore its use is discouraged and may go away.


OPTIONS
       interface
	      The  name	 of the interface.  This is usually a driver name fol-
	      lowed by a unit number, for example eth0 for the first  Ethernet
	      interface.

       up     This  flag  causes the interface to be activated.	 It is implic-
	      itly specified if an address is assigned to the interface.

       down   This flag causes the driver for this interface to be shut down.

       [-]arp Enable or disable the use of the ARP protocol on this interface.

       [-]promisc
	      Enable or disable the promiscuous mode  of  the  interface.   If
	      selected,	 all  packets  on  the network will be received by the
	      interface.

       [-]allmulti
	      Enable or disable all-multicast mode.  If selected,  all	multi-
	      cast packets on the network will be received by the interface.

       metric N
	      This  parameter  sets  the interface metric. It is not available
	      under GNU/Linux.

       mtu N  This parameter sets the Maximum Transfer Unit (MTU) of an inter-
	      face.

       dstaddr addr
	      Set  the	remote	IP  address for a point-to-point link (such as
	      PPP).  This keyword is now obsolete; use the pointopoint keyword
	      instead.

       netmask addr
	      Set the IP network mask for this interface.  This value defaults
	      to the usual class A, B or C network mask (as derived  from  the
	      interface IP address), but it can be set to any value.

       add addr/prefixlen
	      Add an IPv6 address to an interface.

       del addr/prefixlen
	      Remove an IPv6 address from an interface.

       tunnel ::aa.bb.cc.dd
	      Create  a new SIT (IPv6-in-IPv4) device, tunnelling to the given
	      destination.

       irq addr
	      Set the interrupt line used by this device.  Not all devices can
	      dynamically change their IRQ setting.

       io_addr addr
	      Set the start address in I/O space for this device.

       mem_start addr
	      Set  the	start  address	for shared memory used by this device.
	      Only a few devices need this.

       media type
	      Set the physical port or medium type to be used by  the  device.
	      Not all devices can change this setting, and those that can vary
	      in what values  they  support.   Typical	values	for  type  are
	      10base2 (thin Ethernet), 10baseT (twisted-pair 10Mbps Ethernet),
	      AUI (external transceiver) and so on.  The special  medium  type
	      of  auto can be used to tell the driver to auto-sense the media.
	      Again, not all drivers can do this.

       [-]broadcast [addr]
	      If the address argument is given,	 set  the  protocol  broadcast
	      address  for  this  interface.   Otherwise,  set	(or clear) the
	      IFF_BROADCAST flag for the interface.

       [-]pointopoint [addr]
	      This keyword enables the point-to-point mode  of	an  interface,
	      meaning  that  it	 is  a	direct	link between two machines with
	      nobody else listening on it.
	      If the address argument is also given, set the protocol  address
	      of  the  other  side of the link, just like the obsolete dstaddr
	      keyword does.  Otherwise, set or clear the IFF_POINTOPOINT  flag
	      for the interface.

       hw class address
	      Set the hardware address of this interface, if the device driver
	      supports this operation.	The keyword must be  followed  by  the
	      name of the hardware class and the printable ASCII equivalent of
	      the hardware  address.   Hardware	 classes  currently  supported
	      include  ether  (Ethernet), ax25 (AMPR AX.25), ARCnet and netrom
	      (AMPR NET/ROM).

       multicast
	      Set the multicast flag on the interface. This  should  not  nor-
	      mally  be	 needed	 as  the  drivers set the flag correctly them-
	      selves.

       address
	      The IP address to be assigned to this interface.

       txqueuelen length
	      Set the length of the transmit queue of the device. It is useful
	      to  set  this  to	 small	values	for slower devices with a high
	      latency (modem links, ISDN) to prevent fast bulk transfers  from
	      disturbing interactive traffic like telnet too much.


NOTES
       Since kernel release 2.2 there are no explicit interface statistics for
       alias interfaces anymore.  The  statistics  printed  for	 the  original
       address	are shared with all alias addresses on the same device. If you
       want per-address statistics you should add  explicit  accounting	 rules
       for the address using the ipchains(8) command.

       Interrupt  problems  with Ethernet device drivers fail with EAGAIN. See
       http://www.scyld.com/expert/irq-conflict.html for more information.


FILES
       /proc/net/socket
       /proc/net/dev
       /proc/net/if_inet6


BUGS
       Ifconfig uses obsolete kernel interface.	  It  uses  the	 ioctl	access
       method  to  get	the  full  address  information, which limits hardware
       addresses to 8 bytes.  Since an Infiniband address is  20  bytes,  only
       the first 8 bytes of Infiniband address are displayed.

       While  appletalk DDP and IPX addresses will be displayed they cannot be
       altered by this command.


SEE ALSO
       ip(8)


AUTHORS
       Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
       Alan Cox, <Alan.Cox@linux.org>
       Phil Blundell, <Philip.Blundell@pobox.com>
       Andi Kleen



net-tools			14 August 2000			   IFCONFIG(8)