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       ifconfig [interface]
       ifconfig 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
       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 hex-
       adecimal; 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.


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

       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
              selected, all packets on the network will  be  received  by  the

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

              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
              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
       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.




       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)


       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)

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