IFCONFIG(8)

NAME
       ifconfig - configure a network interface

SYNOPSIS
       ifconfig [interface]
       ifconfig interface [aftype] options | address ...

DESCRIPTION
       Ifconfig  is  used to set up (and maintain thereafter) the
       kernel-resident network interfaces.  It is  used  at  boot
       time  to configure most of them to a running state.  After
       that, it is usually only needed  when  debugging  or  when
       system tuning is needed.

       If no arguments are given, ifconfig just displays the sta-
       tus of the currently defined  interfaces.  If  the  single
       interface argument is given, it displays the status of the
       given interface only.  Otherwise, it assumes  that  things
       have to be set up.

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) ax25 (AMPR Packet Radio),
       ddp (Appletalk Phase 2), ipx (Novell IPX) and netrom (AMPR
       Packet radio).

OPTIONS
       interface
              The  name  of the NET interface.  This usually is a
              name like eth0 , sl3  or  something  like  that:  a
              device driver name followed by a unit number.

       up     This flag causes the interface to be activated.  It
              is implicitly specified if the interface is given a
              new address (see below).

       down   This  flag  causes the driver for this interface to
              be shut down, and is useful when things start going
              wrong.

       [-]arp Enable  or  disable  the use of the ARP protocol on
              this interface. If the minus  (-)sign  is  present,
              the flag is turned OFF.

       [-]trailers
              Enable  or  disable the use of trailers on Ethernet
              frames.  This is not used in the current  implemen-
              tation of NET.

       [-]allmulti
              Enable  or  disable  the  promiscuous  mode  of the
              interface.  This means that all incoming frames get
              sent  to  the  network  layer of the system kernel,
              allowing for networking monitoring.

       metric N
              This parameter sets the interface  metric.   It  is
              not  used  at  present, but we implement it for the
              future.

       mtu N  This parameter sets the Maximum Transfer Unit (MTU)
              of an interface.  For Ethernet, this is a number in
              the range of  1000-2000  (default  is  1500).   For
              SLIP,  use  something  between 200 and 4096.  Note,
              that the current implementation does not handle  IP
              fragmentation  yet,  so  you'd  better make the MTU
              large enough!

       dstaddr addr
              Set the "other end"'s  IP  address  in  case  of  a
              Point-To-Point  link,  like  PPP.  This keywords is
              obsoleted by the new 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 deducted from the interface  IP  address),
              but  it can be set to any value for the use of sub-
              netting.

       irq addr
              Set the interrupt line used by  this  device.  Many
              devices don't support dynamic IRQ setting.

       [-]broadcast [addr]
              If the address argument is also given, set the pro-
              tocol broadcast address for this interface.  Other-
              wise,  it  only  sets the IFF_BROADCAST flag of the
              interface.  If the keyword was preceded by a  minus
              (-) sign, then the flag is cleared instead.

       [-]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 (or,
              at least we hope that this is the case, grin :-)
              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,
              it only sets the IFF_POINTOPOINT flag of the inter-
              face.  If the keyword was preceded by a  minus  (-)
              sign, then the flag is cleared instead.

       hw     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  host  name  or IP address (a host name will be
              resolved into an IP  address)  of  that  interface.
              This  parameter  is  required,  although the syntax
              doesn't currently require it.

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

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

AUTHORS
       Fred N. van Kempen, lt;waltje@uwalt.nl.mugnet.org Alan Cox,
       lt;Alan.Cox@linux.org