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
              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.

       [-]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
              (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  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>
 

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