IFCONFIG(8)						     Linux Programmer's Manual						       IFCONFIG(8)

NAME

       ifconfig - configure a network interface

SYNOPSIS

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

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  inter-
	      face.  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.

       [-]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 multicast 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 interface.

       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  (exter-
	      nal 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_BROAD-
	      CAST 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  key-
	      word 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 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) 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 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), iptables(8), ifup(8), interfaces(5).
       http://physics.nist.gov/cuu/Units/binary.html - Prefixes for binary multiples

AUTHORS

       Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
       Alan Cox, <Alan.Cox@linux.org>
       Phil Blundell, <Philip.Blundell@pobox.com>
       Andi Kleen
       Bernd Eckenfels, <net-tools@lina.inka.de>

net-tools							    2007-12-02							       IFCONFIG(8)