ifconfig



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 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  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-
              face.

       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 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).

       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 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

       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, <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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