ifconfig
SYNOPSIS
ifconfig [-v] [-a] [-s] [interface]
ifconfig [-v] interface [aftype] options | address ...
NOTE
This program is obsolete! For replacement check ip addr and ip link.
For statistics use ip -s link.
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 cur-
rently active interfaces. If a single interface argument is given, it
displays the status of the given interface only; if a single -a argu-
ment 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 dot-
ted decimal notation may be decimal, octal, or hexadecimal, as speci-
fied in the ISO C standard (that is, a leading 0x or 0X implies hexa-
decimal; 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.
OPTIONS
-a display all interfaces which are currently available, even if
down
-s display a short list (like netstat -i)
-v be more verbose for some error conditions
interface
The name of the interface. This is usually a driver name fol-
lowed 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 inter-
face use ifconfig eth0:0 down. Note: for every scope (i.e. same
net with address/netmask combination) all aliases are deleted,
[-]allmulti
Enable or disable all-multicast mode. If selected, all multi-
cast packets on the network will be received by the interface.
mtu N This parameter sets the Maximum Transfer Unit (MTU) of an inter-
face.
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 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.
include ether (Ethernet), ax25 (AMPR AX.25), ARCnet and netrom
(AMPR NET/ROM).
multicast
Set the multicast flag on the interface. This should not nor-
mally be needed as the drivers set the flag correctly them-
selves.
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 interactive 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 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 (SIOC-
SIIFLAGS: Resource temporarily unavailable) it is most likely a inter-
rupt conflict. See http://www.scyld.com/expert/irq-conflict.html for
more information.
FILES
/proc/net/dev
/proc/net/if_inet6
BUGS
Ifconfig uses the ioctl access method to get the full address informa-
tion, 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.
SEE ALSO
ip(8), iptables(8)
http://physics.nist.gov/cuu/Units/binary.html - Prefixes for binary
multiples
