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.
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) command.
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)
AUTHORS
Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
Alan Cox, <Alan.Cox@linux.org>
Phil Blundell, <Philip.Blundell@pobox.com>
Andi Kleen, <ak@muc.de>
