INTERFACES(5)		   File formats 	    INTERFACES(5)



NAME
       /etc/network/interfaces	- network interface configuration
       for ifup and ifdown

DESCRIPTION
       /etc/network/interfaces contains network interface config-
       uration	information  for  the  ifup(8) and ifdown(8) com-
       mands. This is where you configure how your system is con-
       nected  to the network, by setting IP addresses, and other
       related information.

       The file can contain comments; all lines starting with `#'
       are  ignored. A line may be extended across multiple lines
       by making the last character a \ in the usual manner.

       The file consists of zero or more "iface",  "mapping"  and
       "auto"  stanzas,  each of which defines one network inter-
       face. Here are some sample stanzas:

	auto lo eth0

	iface lo inet loopback

	mapping eth0
	    script /usr/local/sbin/map-scheme
	    map HOME eth0-home
	    map WORK eth0-work

	iface eth0-home inet static
	    address 192.168.1.1
	    netmask 255.255.255.0

	iface eth0-work inet dhcp

       Stanzas beginning with the word "auto" are used	to  iden-
       tify interfaces that should be brought up automatically on
       system boot. Interface names should follow the word "auto"
       on  the same line. Multiple "auto" stanzas may be used, or
       they may be combined into a single line.

       Stanzas beginning with the  word  "mapping"  are  used  to
       automatically  translate  a physical interface name into a
       logical interface specified  by	an  "iface"  stanza.  The
       first  line of a mapping stanza begins with the word "map-
       ping" followed by the names  of	each  physical	interface
       this  mapping  should apply to. Shell globs (* and ? wild-
       cards) may be used when specifying interfaces.  Each  map-
       ping  must  specify  a  script, which will be run when the
       mapping is applied. In addition, a mapping may specify any
       number  of  "map"  parameters  that  will be passed to the
       script.

       Stanzas defining interfaces start with the  word  "iface".
       The next word is the name of the interface, as used by the
       ifconfig(8) or route(8) commands (ie,  things  like  "lo",
       "eth0", or "ppp0", and "eth1:0").

       The  interface  name  is  followed  by  address family the
       interface uses -- generally this will be "inet" for TCP/IP
       networking,  but  there	is also some support for IPX net-
       working ("ipx"), and IPv6 networking ("inet6").

       Following that is the method used to configure the  inter-
       face.  In the example above, this is "static", which means
       that eth0 is a staticly allocated IPv4 address.

       Further options may follow  the	"iface"  header  line  on
       additional lines in the stanza. These are usually indented
       for clarity (as in the example) but are	not  required  to
       be.

IFACE OPTIONS
       There  are  currently  four standard options available for
       all interfaces, regardless of address  family  or  method.
       These are:

       up command
	      Run  command  after bringing the interface up. This
	      option can be given multiple  times  for	a  single
	      interface.  If so, the commands will be executed in
	      order.  If one of the commands fails, none  of  the
	      others  will  be	executed,  but the interface will
	      remain configured. (You can ensure a command  never
	      fails by suffixing "|| true".)

       pre-up command
	      Run  command before bringing the interface up. This
	      option can be given multiple  times  for	a  single
	      interface.  If so, the commands will be executed in
	      order.  If one of the commands fails, none  of  the
	      others will be executed, and the interface will not
	      be configured. (You  can	ensure	a  command  never
	      fails by suffixing "|| true".)

       down command
	      Run  command before taking the interface down. This
	      option can be given multiple  times  for	a  single
	      interface.  If so, the commands will be executed in
	      order.  If one of the commands fails, none  of  the
	      others will be executed, and the interface will not
	      be deconfigured. (You can ensure	a  command  never
	      fails by suffixing "|| true".)

       post-down command
	      Run  command  after taking the interface down. This
	      option can be given multiple  times  for	a  single
	      interface.  If so, the commands will be executed in
	      order.  If one of the commands fails, none  of  the
	      others  will  be	executed,  but the interface will
	      remain deconfigured.  (You  can  ensure  a  command
	      never fails by suffixing "|| true".)

       Most  methods  require  additional  information,  such  as
       address, and netmask; details about the available  methods
       and the information they require are given below.

       Furthermore  there  exists for each of the above mentioned
       options	   an	  associated	 directory	/etc/net-
       work/if-<option>.d/.   The  contents  of these directories
       are called by run-parts(8), i.e.:

	      run-parts /etc/network/if-<option>.d/

       The exact order of execution for ifup is:

	      1. pre-up option lines

	      2. commands in /etc/network/if-pre-up.d/

	      3. internal commands  (bringing  up  the	interface
		 etc.)

	      4. up option lines

	      5. commands in /etc/network/if-up.d/

       Respectively, for ifdown the execution order is:

	      1. down option lines

	      2. commands in /etc/network/if-down.d/

	      3. internal  commands  (taking  down  the interface
		 etc.)

	      4. post-down option lines

	      5. commands in /etc/network/if-post-down.d/

       The scripts are called with no  command	line  parameters.
       Instead,  passing  values from the interfaces file is done
       via environment variables.   There  are	five  environment
       variable which are always present:

       IFACE  name of the interface this script is called for.

       ADDRFAM
	      address family of the interface

       METHOD method  of  this interface as explained above, e.g.
	      static, dhcp etc.

       MODE   either start or stop, depending on  the  caller  of
	      the scripts being ifup or ifdown.

       PATH   is     always    set    to    a	 default    path:
	      /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

       Additionally,  all  options  (including user-defined) in a
       stanza are exported to the environment, with the exception
       of the already mentioned up/down/pre-up/post-down options.
       For that, an option name undergoes the following transfor-
       mation:

	      o  it is prepended by "IF_"

	      o  all  dashes  ("-")  are  replaced by underscores
		 ("_")

	      o  it is converted to upper case

	      o  all non-alphanumeric characters with the  excep-
		 tion of the dash ("_") are discarded.

       Example:  the  option "foo-bar-!@#4%^2&" gets converted to
       "IF_FOO_BAR_42".

       NB: all exported variables can also  be	used  inside  the
       up/down/pre-up/post-down  commands like normal shell vari-
       ables, e.g.

	      up ip addr add 10.0.0.1 dev ${IFACE}

INET ADDRESS FAMILY
       This section documents the methods available in	the  inet
       address family.

   The loopback Method
       This method may be used to define the IPv4 loopback inter-
       face.

       Options

	      (No options)

   The static Method
       This method may be used to define ethernet interfaces with
       statically allocated IPv4 addresses.

       Options

	      address address
		     Address (dotted quad) required


	      netmask netmask
		     Netmask (dotted quad) required


	      broadcast broadcast_address
		     Broadcast address (dotted quad)

	      network network_address
		     Network  address  (dotted quad) required for
		     2.0.x kernels


	      gateway address
		     Default gateway (dotted quad)

	      pointopoint address
		     Address of other end  point  (dotted  quad).
		     Note the spelling of "point-to".

   The dhcp Method
       This method may be used to obtain an address via DHCP with
       any of the tools: dhclient, pump (2.2.x kernels only),  or
       dhcpcd.	If  you  have a complicated DHCP setup you should
       note that some of these clients use their  own  configura-
       tion  files, rather than obtaining their configuration via
       *ifup*.

       Options

	      hostname hostname
		     Hostname to be requested (pump, dhcpcd)

	      leasehours leastime
		     Preferred lease time in hours (pump)

	      leasetime leasetime
		     Preferred lease time in seconds (dhcpcd)

	      vendor vendor
		     Vendor class identifier (dhcpcd)

	      client client_id
		     Client identifier (dhcpcd)

   The bootp Method
       This method may be used to obtain an address via bootp.

       Options

	      bootfile file
		     Tell the server to use file as the bootfile.

	      server address
		     Use  the  IP  address address to communicate
		     with the server.

	      hwaddr addr
		     Use addr as the hardware address instead  of
		     whatever it really is.

   The ppp Method
       This  method  uses  pon/poff to configure a PPP interface.
       See those commands for details.

       Options

	      provider name
		     Use   name    as	 the	provider    (from
		     /etc/ppp/peers).

   The wvdial Method
       This  method uses wvdial to configure a PPP interface. See
       that command for ore details.

       Options

	      provider name
		     Use   name    as	 the	provider    (from
		     /etc/ppp/peers).

IPX ADDRESS FAMILY
       This  section  documents  the methods available in the ipx
       address family.

   The static Method
       This method may be used to setup an IPX interface.

       Options

	      frame

	      netnum

   The dynamic Method
       This method may be used to setup an IPX interface  dynami-
       cally.

       Options

	      frame

INET6 ADDRESS FAMILY
       This  section documents the methods available in the inet6
       address family.

   The loopback Method
       This method may be used to define the IPv6 loopback inter-
       face.

       Options

	      (No options)

   The static Method
       This  method  may be used to define interfaces with stati-
       cally assigned IPv6 addresses.

       Options

	      address address
		     Address (colon delimited) required


	      netmask mask
		     Netmask (number of bits, eg 64) required


	      gateway address
		     Default gateway (colon delimited)

   The v4tunnel Method
       This method may be used to setup an IPv6-over-IPv4 tunnel.
       It requires the ip command from the iproute package.

       Options

	      address address
		     Address (colon delimited) required


	      netmask mask
		     Netmask (number of bits, eg 64) required


	      endpoint address
		     Address  of other tunnel endpoint (IPv4 dot-
		     ted quad) required


	      gateway address
		     Default gateway (colon delimited)

AUTHOR
       The  ifupdown  suite  was   written   by   Anthony   Towns
       <aj@azure.humbug.org.au>.  This manpage was contributed by
       Joey Hess <joey@kitenet.net>.

SEE ALSO
       ifup(8), ifdown(8), run-parts(8)



ifupdown		  August 10 2000	    INTERFACES(5)