IFCONFIG(8)           Linux System Administrator's Manual          IFCONFIG(8)

       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).  All numbers supplied as parts in IPv4
       dotted decimal notation may be decimal, octal, or hexadecimal, as
       specified in the ISO C standard (that is, a leading 0x or 0X implies
       hexadecimal; otherwise, a leading '0' implies octal; otherwise, the
       number is interpreted as decimal). Use of hexadecimal and octal numbers
       is not RFC-compliant and therefore its use is discouraged.

       -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 syntax like eth0:0 for the first alias
              of eth0. You can use them to assign more addresses. 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;
              you can suppress this behavior when using an alias interface by
              appending an - to the alias (e.g.  eth0:0-).  It is also
              suppressed when using the IPv4 address as the kernel
              will use this to implicitly delete alias interfaces.

       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

       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.

       tunnel ::aa.bb.cc.dd
              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 iptables(8) command.

       Since net-tools 1.60-4 ifconfig is printing byte counters and human
       readable counters with IEC 60027-2 units. So 1 KiB are 2^10 byte. Note,
       the numbers are truncated to one decimal (which can by quite a large
       error if you consider 0.1 PiB is 112.589.990.684.262 bytes :)

       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.


       Ifconfig uses the ioctl access method to get the full address
       information, which limits hardware addresses to 8 bytes.  Because
       Infiniband hardware address has 20 bytes, only the first 8 bytes are
       displayed correctly.  Please use ip link command from iproute2 package
       to display link layer informations including the hardware address.

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

       route(8), netstat(8), arp(8), rarp(8), iptables(8), ifup(8),
       http://physics.nist.gov/cuu/Units/binary.html - Prefixes for binary

       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                         2008-10-03                       IFCONFIG(8)