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       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, <>

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