ifconfig (8)


       ifconfig - configure a network interface


       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).


              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.

       metric N
              This parameter sets the interface metric.

       mtu N  This parameter sets the Maximum Transfer Unit (MTU) of an inter-
              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 nor-
              mally be needed as the drivers  set  the  flag  correctly  them-
              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://cesdis.gsfc.nasa.gov/linux/misc/irq-conflict.html    for    more




       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)