IFTAB(5) Linux Programmer's Manual IFTAB(5)NAMEiftab - static information about the network interfaces
DESCRIPTION
The file /etc/iftab contains descriptive information about the various
network interfaces. iftab is only used by the program ifrename(8) to
assign a consistent network interface name to each network interface.
/etc/iftab defines a set of mappings. Each mapping contains an inter‐
face name and a set of selectors. The selectors allow ifrename to iden‐
tify each network interface on the system. If a network interface
matches all descriptors of a mapping, ifrename attempt to change the
name of the interface to the interface name given by the mapping.
MAPPINGS
Each mapping is described on a separate line, it starts with an inter‐
face name, and contains a set of descriptors, separated by space or
tabs.
The relationship between descriptors of a mapping is a logical and. A
mapping matches a network interface only is all the descriptors match.
If a network interface doesn't support a specific descriptor, it won't
match any mappings using this descriptor.
If you want to use alternate descriptors for an interface name (logical
or), specify two different mappings with the same interface name (one
on each line). Ifrename always use the first matching mapping starting
from the end of iftab, therefore more restrictive mapping should be
specified last.
INTERFACE NAME
The first part of each mapping is an interface name. If a network
interface matches all descriptors of a mapping, ifrename attempt to
change the name of the interface to the interface name given by the
mapping.
The interface name of a mapping is either a plain interface name (such
as eth2 or wlan1) or a interface name pattern containing a single wild‐
card (such as eth* or wlan*). In case of wildcard, the kernel replace
the '*' with the lowest available integer making this interface name
unique. Note that wildcard is only supported for kernel 2.6.1 and
2.4.30 and later.
It is discouraged to try to map interfaces to default interfaces names
such as eth0, wlan0 or ppp0. The kernel use those as the default name
for any new interface, therefore most likely an interface will already
use this name and prevent ifrename to use it. Even if you use takeover,
the interface may already be up in some cases. Not using those name
will allow you to immediately spot unconfigured or new interfaces.
Good names are either totally unique and meaningfull, such as mydsl or
privatehub, or use larger integer, such as eth5 or wlan5. The second
type is usually easier to integrate in various network utilities.
DESCRIPTORS
Each descriptor is composed of a descriptor name and descriptor value.
Descriptors specify a static attribute of a network interface, the goal
is to uniquely identify each piece of hardware.
Most users will only use the mac selector, other selectors are for more
specialised setup.
mac mac address
Matches the MAC Address of the interface with the specified MAC
address. The MAC address of the interface can be shown using
ifconfig(8) or ip(8). The specified MAC address may contain a
'*' for wilcard matching.
This is the most common selector, as most interfaces have a
unique MAC address allowing to identify network interfaces with‐
out ambiguity. However, some interfaces don't have a valid MAC
address until they are brought up, in such case using this
selector is tricky.
arp arp type
Matches the ARP Type (also called Link Type) of the interface
with the specified ARP type. The ARP Type of the interface can
be shown using ifconfig(8) or ip(8).
This selector is useful when a driver create multiple network
interfaces for a single network card.
driver driver name
Matches the Driver Name of the interface with the specified
driver name. The Driver Name of the interface can be shown using
ethtool -i(8).
businfo bus information
Matches the Bus Information of the interface with the specified
bus information. The Bus Information of the interface can be
shown using ethtool -i(8).
firmware firmware revision
Matches the Firmware Revision of the interface with the firmware
revision information. The Firmware Revision of the interface can
be shown using ethtool -i(8).
baseaddress base address
Matches the Base Address of the interface with the specified
base address. The Base Address of the interface can be shown
using ifconfig(8).
Because most cards use dynamic allocation of the Base Address,
this selector is only useful for ISA and EISA cards.
irq irq line
Matches the IRQ Line (interrupt) of the interface with the spec‐
ified IRQ line. The IRQ Line of the interface can be shown using
ifconfig(8).
Because there are IRQ Lines may be shared, this selector is usu‐
ally not sufficient to uniquely identify an interface.
iwproto wireless protocol
Matches the Wireless Protocol of the interface with the speci‐
fied wireless protocol. The Wireless Protocol of the interface
can be shown using iwconfig(8).
This selector is only supported on wireless interfaces and is
not sufficient to uniquely identify an interface.
pcmciaslot pcmcia slot
Matches the Pcmcia Socket number of the interface with the spec‐
ified slot number. Pcmcia Socket number of the interface can be
shown using cardctl ident(8).
This selector is usually only supported on 16 bits cards, for 32
bits cards it is advised to use the selector businfo.
SYSFS{filename} value
Matches the sysfs attribute given by filename to the specified
value. sysfs attributes of the interface can be read in one of
the directory in the directory /sys/class/net/. For example,
the filename address is the MAC address of the device and should
be identical to the selector mac.
The sysfs filesystem is only supported with 2.6.X kernel and
need to be mounted. sysfs selectors are not as efficient as
other selectors, therefore they should be avoided for maximum
performance.
EXAMPLE
# This is a comment
eth2 mac 08:00:09:DE:82:0E
eth3 driver wavelan interrupt 15 baseaddress 0x390
eth4 driver pcnet32 businfo 0000:02:05.0
air* mac 00:07:0E:* arp 1
myvpn SYSFS{address} 00:10:83:*
AUTHOR
Jean Tourrilhes - jt@hpl.hp.com
FILES
/etc/iftab
SEE ALSOifrename(8), ifconfig(8), ip(8), ethtool(8), iwconfig(8).
wireless-tools 01 March 2004 IFTAB(5)