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

       ifconfig	- configure a network interface

       ifconfig	[-v] [-a] [-s] [interface]
       ifconfig	[-v] interface [aftype]	options	| address ...

       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

       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 de-
       coding and displaying all protocol addresses.  Currently	supported  ad-
       dress families include inet (TCP/IP, default), inet6 (IPv6), ax25 (AMPR
       Packet Radio), ddp (Appletalk Phase 2), ipx  (Novell  IPX)  and	netrom
       (AMPR Packet radio).

       -a     display  all  interfaces	which are currently available, even if

       -s     display a	short list (like netstat -i)

       -v     be more verbose for some error conditions

	      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. If your kernel	supports  alias	 interfaces,  you  can
	      specify  them  with  eth0:0 for the first	alias of eth0. You can
	      use them to assign a second address. To delete an	 alias	inter-
	      face use ifconfig	eth0:0 down.  Note: for	every scope (i.e. same
	      net with address/netmask combination) all	aliases	 are  deleted,
	      if you delete the	first (primary).

       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.

	      Enable or	disable	the promiscuous	mode of	the interface.	If se-
	      lected,  all  packets on the network will	be received by the in-

	      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.

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

       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

       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.

	      Create a new SIT (IPv6-in-IPv4) device, tunnelling to the	 given

       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 ad-
	      dress  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  no-
	      body 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 in-
	      clude ether (Ethernet), ax25 (AMPR  AX.25),  ARCnet  and	netrom
	      (AMPR NET/ROM).

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

	      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  la-
	      tency  (modem  links,  ISDN) to prevent fast bulk	transfers from
	      disturbing interactive traffic like telnet too much.

       Since kernel release 2.2	there are no explicit interface	statistics for
       alias  interfaces  anymore. The statistics printed for the original ad-
       dress 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) or	iptables(8) command.

       Since net-tools 1.60-4 ifconfig is printing  byte  counters  and	 human
       readable	counters with IEC 60027-2 units. So 1 KiB are 2^10 byte. Note,
       the numbers are truncated to one	decimal	(which can by  quite  a	 large
       error if	you consider 0.1 PiB is	112.589.990.684.262 bytes :)

       Interrupt problems with Ethernet	device drivers fail with EAGAIN	(SIOC-
       SIIFLAGS: Resource temporarily unavailable) it is most likely a	inter-
       rupt  conflict.	See for
       more information.


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

       route(8),   netstat(8),	 arp(8),  rarp(8),  ipchains(8),  iptables(8),
       ifup(8),	interfaces(5).  -	 Prefixes  for	binary

       Fred N. van Kempen, <>
       Alan Cox, <>
       Phil Blundell, <>
       Andi Kleen
       Bernd Eckenfels,	<>

net-tools			  2007-12-02			   IFCONFIG(8)


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