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NAME    [Toc]    [Back]

       ifconfig - configure a network interface

SYNOPSIS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

       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  currently
  active interfaces.  If a single interface argument is given, it
       displays the status of the given interface only; if a single  -a  argument
  is  given,  it  displays the status of all interfaces, even those
       that are down.  Otherwise, it configures an interface.

Address Families    [Toc]    [Back]

       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).

OPTIONS    [Toc]    [Back]

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

       up     This  flag  causes the interface to be activated.  It is implicitly
 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
	      selected,  all  packets  on  the network will be received by the

	      Enable or disable all-multicast mode.  If selected,  all	multicast
 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 interface.

       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.

       tunnel aa.bb.cc.dd
	      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
	      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).

	      Set  the	multicast  flag on the interface. This should not normally
 be needed as the drivers  set  the	flag  correctly  themselves.

	      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    [Toc]    [Back]

       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.

       Since net-tools 1.60-4 ifconfig	is  printing  byte  counters  with  SI
       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	interrupt
  conflict.	See  http://www.scyld.com/expert/irq-conflict.html for
       more information.

FILES    [Toc]    [Back]


BUGS    [Toc]    [Back]

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

SEE ALSO    [Toc]    [Back]

       route(8), netstat(8), arp(8), rarp(8), ipchains(8)
       http://physics.nist.gov/cuu/Units/binary.html  -  Prefixes  for	binary

AUTHORS    [Toc]    [Back]

       Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
       Alan Cox, <Alan.Cox@linux.org>
       Phil Blundell, <Philip.Blundell@pobox.com>
       Andi Kleen;
       Bernd Eckenfels, <net-tools@lina.inka.de>

net-tools			  11 Nov 2001			   IFCONFIG(8)
[ Back ]
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