IFCONFIG linux command manual

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



NAME
       ifconfig - configure a network interface

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

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).

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 inter-
              face.

       [-]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.

       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  key-
              word 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  Ether-
              net), 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 use-
              ful 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
       While appletalk DDP and IPX addresses will be displayed they cannot be
       altered by this command.

SEE ALSO
       route(8), netstat(8), arp(8), rarp(8), ipchains(8)

AUTHORS
       Fred N. van Kempen, 
       Alan Cox, 
       Phil Blundell, 
       Andi Kleen



net-tools                       14 August 2000                    IFCONFIG(8)