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IFCONFIG(8)                              Linux System Administrator's Manual                              IFCONFIG(8)



NAME
       ifconfig - configure a network interface

SYNOPSIS
       ifconfig [-v] [-a] [-s] [interface]
       ifconfig [-v] 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       This program is obsolete!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
       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 currently active interfaces.  If a single
       interface 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 inter‐
       face.


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
       (Novell  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
       hexadecimal;  otherwise, a leading '0' implies octal; otherwise, the number is interpreted as decimal). Use of
       hexadecimal and octal numbers is not RFC-compliant and therefore its use is discouraged.

OPTIONS
       -a     display all interfaces which are currently available, even if down

       -s     display a short list (like netstat -i)

       -v     be more verbose for some error conditions

       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. If your kernel supports alias interfaces, you can specify them with
              eth0:0 for the first alias of eth0. You can use them to assign a second address.  To  delete  an  alias
              interface use ifconfig eth0:0 down.  Note: for every scope (i.e. same net with address/netmask combina‐
              tion) all aliases are deleted, if you delete the first (primary).

       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.
              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 set‐
              ting, 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 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

       Interrupt  problems with Ethernet device drivers fail with EAGAIN (SIOCSIIFLAGS: Resource temporarily unavail‐
       able) it is most likely a  interrupt  conflict.  See  http://www.scyld.com/expert/irq-conflict.html  for  more
       information.

FILES
       /proc/net/dev
       /proc/net/if_inet6

BUGS
       Ifconfig  uses the ioctl access method to get the full address information, which limits hardware addresses to
       8 bytes.  Because Infiniband hardware address has 20 bytes, only the first 8 bytes  are  displayed  correctly.
       Please  use  ip  link  command from iproute2 package to display link layer informations including the hardware
       address.

       While appletalk DDP and IPX addresses will be displayed they cannot be altered by this command.

SEE ALSO
       ip(8), iptables(8)
       http://physics.nist.gov/cuu/Units/binary.html - Prefixes for binary multiples

AUTHORS
       Fred N. van Kempen, <[email protected]>
       Alan Cox, <[email protected]>
       Phil Blundell, <[email protected]>
       Andi Kleen
       Bernd Eckenfels, <[email protected]>



net-tools                                             2008-10-03                                          IFCONFIG(8)