ifconfig – configure a network interface
ifconfig interface [aftype] options | address …
This program is obsolete!
For replacement check ip addr and ip link.
For statistics use ip -s link.
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,
displays the status of the currently active interfaces. If
argument is given, it displays the status of the given interface
only; if a single
argument is given, it displays the status of all interfaces, even
those that are down. Otherwise, it configures an interface.
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
(AMPR Packet Radio),
(Appletalk Phase 2),
(Novell IPX) and
(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 hexamedial and octal numbers
is not RFC-compliant and therefore its use is discouraged and may go away.
for the first Ethernet interface.
mode of the interface. If selected, all packets on the network will
be received by the interface.
mode. If selected, all multicast packets on the network will be
received by the interface.
(twisted-pair 10Mbps Ethernet),
(external transceiver) and so on. The special medium type of
can be used to tell the driver to auto-sense the media. Again, not
all drivers can do this.
flag for the interface.
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
keyword does. Otherwise, set or clear the
flag for the interface.
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
Interrupt problems with Ethernet device drivers fail with EAGAIN. See
for more information.
Ifconfig uses obsolete kernel interface.
It uses the ioctl access method to get the full address information,
which limits hardware addresses to 8 bytes.
Since an Infiniband address is 20 bytes,
only the first 8 bytes of Infiniband address are displayed.
While appletalk DDP and IPX addresses will be displayed they cannot be
altered by this command.
Fred N. van Kempen, <[email protected]>
Alan Cox, <[email protected]>
Phil Blundell, <[email protected]>