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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       This program is obsolete!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 inter-
       faces 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 currently active interfaces.  If a single inter-
       face  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
       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 fami-
       lies include inet (TCP/IP, default), inet6 (IPv6), ax25 (AMPR Packet Radio), ddp (Appletalk Phase 2), ipx (Nov-
       ell  IPX) and netrom (AMPR Packet radio).  All numbers supplied as parts in IPv4 dotted decimal notation may be
       decimal, octal, or hexadecimal, as specified in the ISO C standard (that is, a leading 0x or  0X  implies  hex-
       adecimal; otherwise, a leading '0' implies octal; otherwise, the number is interpreted as decimal). Use of hex-
       amedial 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 followed by a unit number,  for  example  eth0
              for the first Ethernet interface.

       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.

       [-]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  multicast 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 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 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 Ether-
              net), 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 normally be needed as the drivers set the flag
              correctly themselves.

       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 interac-
              tive traffic like telnet too much.


NOTES
       Since kernel release 2.2 there are no explicit interface statistics for alias interfaces anymore.  The  statis-
       tics  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-con-
       flict.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, <waltjeATuwalt.org>
       Alan Cox, <Alan.CoxATlinux.org>
       Phil Blundell, <Philip.BlundellATpobox.com>
       Andi Kleen



net-tools                       14 August 2000                     IFCONFIG(8)