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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 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 despite its potential prob‐
       lems, 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
	      ifconfig(8) or ip(8).
	      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 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 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) 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 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.

       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 subdirectories.

       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 perfor‐
       mance.

       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)
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