IFTAB(5)						     Linux Programmer's Manual							  IFTAB(5)

NAME

       iftab - 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 interface name and a set of selectors.  The  selectors  allow  ifrename	to
       identify  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 interface 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
       wildcard (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 inter-
       faces.
       Good names are either totally unique and meaningfull, such as mydsl or privatehub, or use larger integer, such as eth5 or wlan5.  The  sec-
       ond 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 despite its potential problems, other selectors are for more specialised  setup.  Most  selectors
       accept a '*' in the selector value for wilcard matching, and most selectors are case insensitive.

       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 ifcon-
	      fig(8) or ip(8).
	      This is the most common selector, as most interfaces have a unique MAC address allowing to identify network interfaces without ambi-
	      guity.   However,  some  interfaces  don't  have	a valid MAC address until they are brought up, in such case using this selector is
	      tricky or impossible.

       arp arp type
	      Matches the ARP Type (also called Link Type) of the interface with the specified ARP type as a number. The ARP Type of the interface
	      can be shown using ifconfig(8) or ip(8), the link/ether type correspond to 1 and the link/ieee802.11 type correspond to 801.
	      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 specified 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 usually not sufficient to uniquely identify an interface.

       iwproto wireless protocol
	      Matches the Wireless Protocol of the interface with the specified wireless protocol. The Wireless Protocol of the interface  can	be
	      shown using iwconfig(8) or iwgetid(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 specified 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.

       prevname previous interface name
	      Matches the name of the interface prior to renaming with the specified oldname.
	      This selector should be avoided as the previous interface name may vary  depending  on  various  condition.  A  system/kernel/driver
	      update may change the original name. Then, ifrename or another tool may rename it prior to the execution of this selector.

       SYSFS{filename} value
	      Matches  the  content  the sysfs attribute given by filename to the specified value. For symlinks and parents directories, match the
	      actual directory name of the sysfs attribute given by filename to the specified value.
	      A list of the most useful sysfs attributes is given in the next section.

SYSFS DESCRIPTORS

       Sysfs attributes for a specific interface are located on most systems in the directory named after that interface at /sys/class/net/.  Most
       sysfs  attribute  are  files, and their values can be read using cat(1) or more(1).  It is also possible to match attributes in subdirecto-
       ries.

       Some sysfs attributes are symlinks, pointing to another directory in sysfs. If the attribute filename is  a  symlink  the  sysfs  attribute
       resolves  to  the  name	of  the directory pointed by the symlink using readlink(1).  The location is a directory in the sysfs tree is also
       important. If the attribute filename ends with /.., the sysfs attribute resolves to the real name of the parent directory using pwd(1).

       The sysfs filesystem is only supported with 2.6.X kernel and need to be mounted (usually in /sys).  sysfs selectors are not as efficient as
       other selectors, therefore they should be avoided for maximum performance.

       These are common sysfs attributes and their corresponding ifrename descriptors.

       SYSFS{address} value
	      Same as the mac descriptor.

       SYSFS{type} value
	      Same as the arp descriptor.

       SYSFS{device} value
	      Valid only up to kernel 2.6.20. Same as the businfo descriptor.

       SYSFS{..} value
	      Valid only from kernel 2.6.21. Same as the businfo descriptor.

       SYSFS{device/driver} value
	      Valid only up to kernel 2.6.20. Same as the driver descriptor.

       SYSFS{../driver} value
	      Valid only from kernel 2.6.21. Same as the driver descriptor.

       SYSFS{device/irq} value
	      Valid only up to kernel 2.6.20. Same as the irq descriptor.

       SYSFS{../irq} value
	      Valid only from kernel 2.6.21. Same as the irq descriptor.

EXAMPLES

       # 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:* SYSFS{type} 1
       bcm*	 SYSFS{device} 0000:03:00.0 SYSFS{device/driver} bcm43xx
       bcm*	 SYSFS{..} 0000:03:00.0 SYSFS{../driver} bcm43xx

AUTHOR

       Jean Tourrilhes - jt@hpl.hp.com

FILES

       /etc/iftab

SEE ALSO

       ifrename(8), ifconfig(8), ip(8), ethtool(8), iwconfig(8).

wireless-tools							 26 February 2007							  IFTAB(5)