Man Linux: Main Page and Category List


       ifconfig - configure a network interface


       ifconfig [-v] [-a] [-s] [interface]
       ifconfig [-v] 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
       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 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).


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

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

       -v     be more verbose for some error conditions

              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  combination)  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.

              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
              multicast packets  on  the  network  will  be  received  by  the

       metric N
              This parameter sets the interface metric.

       mtu N  This  parameter  sets  the  Maximum  Transfer  Unit  (MTU) of an

       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

       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.

              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
              normally be  needed  as  the  drivers  set  the  flag  correctly

              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.


       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) or iptables(8) command.

       Interrupt problems  with  Ethernet  device  drivers  fail  with  EAGAIN
       (SIOCSIIFLAGS:  Resource  temporarily  unavailable) it is most likely a
       interrupt conflict.  See
       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),   iptables(8),
       ifup(8), interfaces(5).  -  Prefixes  for  binary


       Fred N. van Kempen, <>
       Alan Cox, <>
       Phil Blundell, <>
       Andi Kleen
       Bernd Eckenfels, <>