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  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 dis­
       plays 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 recog­
       nized 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 followed by a unit number, for  example
              eth0 for the first Ethernet interface.

       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 set­
              ting.

       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 pro­
              tocol 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  inter­
              active traffic like telnet too much.

FILES

       /proc/net/socket
       /proc/net/dev
       /proc/net/if_inet6
       /etc/init.d/network

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)

AUTHORS

       Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
       Alan Cox, <Alan.Cox@linux.org>
       Phil Blundell, <Philip.Blundell@pobox.com>