INTERFACES(5)			 File formats			 INTERFACES(5)



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

DESCRIPTION
       /etc/network/interfaces contains network interface configuration infor
       mation  for the ifup(8) and ifdown(8) commands.	This is where you con
       figure how your system is connected to the network.

       Lines starting with # are ignored. Note that end-of-line comments are
       NOT supported, comments must be on a line of their own.

       A line may be extended across multiple lines by making the last charac
       ter a backslash.

       The file consists of  zero  or  more  "iface",  "mapping",  "auto"  and
       "allow-" stanzas. Here is an example.

	      auto lo eth0
	      allow-hotplug eth1

	      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
		   up flush-mail

	      iface eth0-work inet dhcp

	      iface eth1 inet dhcp

       Lines  beginning with the word "auto" are used to identify the physical
       interfaces to be brought up when ifup is run with the -a option.  (This
       option  is  used by the system boot scripts.)  Physical interface names
       should follow the word "auto" on the same line.	There can be  multiple
       "auto"  stanzas.   ifup	brings	the  named  interfaces up in the order
       listed.

       Lines beginning with "allow-" are  used	to  identify  interfaces  that
       should  be  brought  up automatically by various subsytems. This may be
       done using a command such as "ifup --allow=hotplug  eth0  eth1",  which
       will  only  bring up eth0 or eth1 if it is listed in an "allow-hotplug"
       line. Note that "allow-auto" and "auto" are synonyms.

       Stanzas beginning with the word "mapping" are used to determine	how  a
       logical interface name is chosen for a physical interface that is to be
       brought up.  The first line of a mapping stanza consists  of  the  word
       "mapping"  followed  by	a  pattern in shell glob syntax.  Each mapping
       stanza must contain a script definition.  The named script is run  with
       the  physical  interface  name as its argument and with the contents of
       all following "map" lines (without the leading  "map")  in  the	stanza
       provided to it on its standard input. The script must print a string on
       its standard output before exiting.  See  /usr/share/doc/ifupdown/exam
       ples for examples of what the script must print.

       Mapping a name consists of searching the remaining mapping patterns and
       running the script corresponding to the first match; the script outputs
       the name to which the original is mapped.

       ifup  is  normally  given  a  physical  interface  name	as  its  first
       non-option argument.  ifup also uses this name as the  initial  logical
       name  for  the  interface  unless it is accompanied by a  suffix of the
       form =LOGICAL, in which case ifup chooses LOGICAL as the initial  logi
       cal name for the interface.  It then maps this name, possibly more than
       once according to successive mapping specifications,  until no  further
       mappings  are  possible.   If  the  resulting  name is the name of some
       defined logical interface then ifup attempts to bring up  the  physical
       interface  as  that  logical  interface.   Otherwise ifup exits with an
       error.

       Stanzas defining logical interfaces start with a line consisting of the
       word  "iface" followed by the name of the logical interface.  In simple
       configurations without mapping stanzas this name should simply  be  the
       name  of  the  physical	interface  to which it is to be applied.  (The
       default mapping script is, in effect, the echo command.)  The interface
       name  is  followed by the name of the address family that the interface
       uses.  This will be "inet" for TCP/IP networking,  but  there  is  also
       some support for IPX networking ("ipx"), and IPv6 networking ("inet6").
       Following that is the name of the method used to configure  the	inter
       face.

       Additional  options  can  be  given  on subsequent lines in the stanza.
       Which options are available  depends  on  the  family  and  method,  as
       described  below.   Additional  options	can be made available by other
       Debian packages.  For example, the wireless-tools package makes	avail
       able a number of options prefixed with "wireless-" which can be used to
       configure  the  interface  using  iwconfig(8).	(See  wireless(7)  for
       details.)

       Options	are usually indented for clarity (as in the example above) but
       are not required to be.

IFACE OPTIONS
       The following "command" options are  available  for  every  family  and
       method.	 Each of these options can be given multiple times in a single
       stanza, in which case the commands are executed in the order  in  which
       they  appear  in  the stanza.  (You can ensure a command never fails by
       suffixing "|| true".)

       pre-up command
	      Run command before bringing the interface up.  If  this  command
	      fails then ifup aborts, refraining from marking the interface as
	      configured, prints an error message, and exits  with  status  0.
	      This behavior may change in the future.

       up command

       post-up command
	      Run  command  after  bringing the interface up.  If this command
	      fails then ifup aborts, refraining from marking the interface as
	      configured  (even  though it has really been configured), prints
	      an error message, and exits with status 0.   This  behavior  may
	      change in the future.

       down command

       pre-down command
	      Run  command  before taking the interface down.  If this command
	      fails then ifdown aborts, marks the  interface  as  deconfigured
	      (even  though  it  has  not really been deconfigured), and exits
	      with status 0.  This behavior may change in the future.

       post-down command
	      Run command after taking the interface down.   If  this  command
	      fails  then  ifdown aborts, marks the interface as deconfigured,
	      and exits with status  0.   This	behavior  may  change  in  the
	      future.

       There  exists  for  each  of  the  above  mentioned options a directory
       /etc/network/if-.d/ the scripts in which are run (with no argu
       ments) using run-parts(8) after the option itself has been processed.

       All  of	these  commands have access to the following environment vari
       ables.

       IFACE  physical name of the interface being processed

       LOGICAL
	      logical name of the interface being processed

       ADDRFAM
	      address family of the interface

       METHOD method of the interface (e.g., static)

       MODE   start if run from ifup, stop if run from ifdown

       PHASE  as per MODE, but with finer granularity, distinguishing the pre-
	      up, post-up, pre-down and post-down phases.

       VERBOSITY
	      indicates  whether --verbose was used; set to 1 if so, 0 if not.

       PATH   the  command   search   path:   /usr/local/sbin:/usr/local/bin:
	      /usr/sbin:/usr/bin:/sbin:/bin

       Additionally,  all  options given in an interface definition stanza are
       exported to the environment in upper case with "IF_" prepended and with
       hyphens	converted  to underscores and non-alphanumeric characters dis
       carded.

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

   The loopback Method
       This method may be used to define the IPv4 loopback interface.

       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

	      metric metric
		     Routing metric for default gateway (integer)

	      gateway address
		     Default gateway (dotted quad)

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

	      media type
		     Medium type, driver dependent

	      hwaddress class address
		     Hardware  Address. class is one of ether, ax25, ARCnet or
		     netrom. address is dependent on the above choice.

	      mtu size
		     MTU size

   The manual Method
       This method may be used to define interfaces for which no configuration
       is done by default. Such interfaces can be configured manually by means
       of up and down commands or /etc/network/if-*.d scripts.

       Options

	      (No options)

   The dhcp Method
       This method may be used to obtain an address via DHCP with any  of  the
       tools:  dhclient, pump, udhcpc, dhcpcd. (They have been listed in their
       order of precedence.) If you have a complicated DHCP setup  you	should
       note  that  some of these clients use their own configuration files and
       do not obtain their configuration information via ifup.

       Options

	      hostname hostname
		     Hostname to be requested (pump, dhcpcd, udhcpc)

	      leasehours leasehours
		     Preferred lease time in hours (pump)

	      leasetime leasetime
		     Preferred lease time in seconds (dhcpcd)

	      vendor vendor
		     Vendor class identifier (dhcpcd)

	      client client
		     Client identifier (dhcpcd, udhcpc)

	      hwaddress class address
		     Hardware Address. class is one of ether, ax25, ARCnet  or
		     netrom. address is dependent on this choice.

   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 com
       mands 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 more 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.  It  requires  the
       ipx_interface command.

       Options

	      frame type
		     type of ethernet frames to use (e.g. 802.2)

	      netnum id
		     Network number

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

       Options

	      frame type
		     type of ethernet frames to use (e.g. 802.2)

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

   The loopback Method
       This method may be used to define the IPv6 loopback interface.

       Options

	      (No options)

   The static Method
       This method may be used to define interfaces with  statically  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)

	      media type
		     Medium type, driver dependent

	      hwaddress class address
		     Hardware  Address. class is one of ether, ax25, ARCnet or
		     netrom. address is dependent on this choice.

	      mtu size
		     MTU size

   The manual Method
       This method may be used to define interfaces for which no configuration
       is done by default. Such interfaces can be configured manually by means
       of up and down commands or /etc/network/if-*.d scripts.

       Options

	      (No options)

   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)

	      netmask mask
		     Netmask (number of bits, eg 64)

	      endpoint address
		     Address  of  other  tunnel  endpoint  (IPv4  dotted quad)
		     required

	      local address
		     Address of the local endpoint (IPv4 dotted quad)

	      gateway address
		     Default gateway (colon delimited)

	      ttl time
		     TTL setting

KNOWN BUGS/LIMITATIONS
       The ifup and ifdown programs work with so-called  "physical"  interface
       names.	These  names are assigned to hardware by the kernel.  Unfortu
       nately it can happen that the kernel assigns different physical	inter
       face  names  to the same hardware at different times; for example, what
       was called "eth0" last time you booted is now called  "eth1"  and  vice
       versa.	This creates a problem if you want to configure the interfaces
       appropriately.  A way to deal with  this  problem  is  to  use  mapping
       scripts that choose logical interface names according to the properties
       of the interface hardware.  See the get-mac-address.sh  script  in  the
       examples  directory  for an example of such a mapping script.  See also
       Debian bug #101728.

       It is not currently possible to divide up /etc/network/interfaces  into
       multiple  files.   A feature that would make this possible is some sort
       of inclusion directive.	No such feature exists in the current ifupdown
       program.  For more information see Debian bug #159884.

AUTHOR
       The   ifupdown  suite  was  written  by	Anthony  Towns	.    This   manpage	was   contributed   by	  Joey	  Hess
       .

SEE ALSO
       ifup(8), iwconfig(8), run-parts(8).

       For  advice  on configuring this package read the Network Configuration
       chapter	 of   the    Debian    Reference    manual,    available    at
       http://www.debian.org/doc/manuals/reference/ch-gateway.en.html	or  in
       the debian-reference-en package.

       Examples  of   how   to	 set   up   interfaces	 can   be   found   in
       /usr/share/doc/ifupdown/examples/network-interfaces.



ifupdown			 5 April 2004			 INTERFACES(5)