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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  information  for the
       ifup(8) and ifdown(8) commands.	This is where you configure 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 character a backslash.

       The file consists of zero or more "iface", "mapping", "auto", "allow-" and "source"  stan-
       zas. Here is an example.
       auto lo eth0
       allow-hotplug eth1

       iface lo inet loopback

       source interfaces.d/machine-dependent

       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.

       Lines  beginning with "source" are used to include stanzas from other files, so configura-
       tion can be split into many files. The word "source" is followed by the path of file to be
       sourced. Shell wildcards can be used.  (See wordexp(3) for details.)

       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/ifup-
       down/examples 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"  fol-
       lowed  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 interface.

       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
       available 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  mes-
	      sage, 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 behav-
	      ior may change in the future.

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

       All of these commands have access to the following environment variables.

       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 discarded.

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 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/netmask) required

	      netmask mask
		     Netmask (dotted quad or CIDR)

	      broadcast broadcast_address
		     Broadcast address (dotted quad)

	      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".

	      hwaddress address
		     Link local address.

	      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 configura-
       tion 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 address
		     Hardware Address.

   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 tunnel Method
       This method is used to create GRE or IPIP tunnels. You need to have the ip binary from the
       iproute	package.  For  GRE  tunnels, you will need to load the ip_gre module and the ipip
       module for IPIP tunnels.

       Options

	      address address
		     Local address (dotted quad) required

	      mode type
		     Tunnel type (either GRE or IPIP) required

	      endpoint address
		     Address of other tunnel endpoint required

	      dstaddr address
		     Remote address (remote address inside tunnel)

	      local address
		     Address of the local endpoint

	      gateway address
		     Default gateway

	      ttl time
		     TTL setting

	      mtu size
		     MTU size

   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).

	      unit number
		     Use number as the ppp unit number.

	      options string
		     Pass string as additional options to pon.

   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).

   The ipv4ll Method
       This method uses avahi-autoipd to configure an interface with an IPv4  Link-Layer  address
       (169.254.0.0/16	family). This method is also known as "APIPA" or "IPAC", and often collo-
       quially referred to as "Zeroconf address".

       Options

	      (No options)

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 family.

   The auto Method
       This method may be used to define interfaces with automatically assigned  IPv6  addresses.
       Using this method on its own doesn't mean that RDNSS options will be applied, too. To make
       this happen, rdnssd daemon must be installed, properly configured and running.  If  state-
       less DHCPv6 support is turned on, then additional network configuration parameters such as
       DNS and NTP servers will be retrieved from a DHCP server.

       Options

	      privext int
		     Privacy extensions (RFC3041) (0=off, 1=assign, 2=prefer)

	      dhcp int
		     Use stateless DHCPv6 (0=off, 1=on)

   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.  By
       default, stateless autoconfiguration is disabled for this interface.

       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 address
		     Hardware address

	      mtu size
		     MTU size

	      accept_ra int
		     Accept router advertisements (0=off, 1=on)

	      autoconf int
		     Perform stateless autoconfiguration (0=off, 1=on)

	      privext int
		     Privacy extensions (RFC3041) (0=off, 1=assign, 2=prefer)

   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 network interface configuration via stateful DHCPv6 with
       dhclient. In stateful DHCPv6, the DHCP server is responsible for  assigning  addresses  to
       clients.

       Options

	      hwaddress address
		     Hardware address

   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

	      mtu size
		     MTU size

   The 6to4 Method
       This method may be used to setup an 6to4 tunnel. It  requires  the  ip  command	from  the
       iproute package.

       Options

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

	      ttl time
		     TTL setting

	      mtu size
		     MTU size

CAN ADDRESS FAMILY
       This section documents the methods available in the can address family.

   The static Method
       This  method  may be used to setup an Controller Area Network (CAN) interface. It requires
       the the ip command from the iproute package.

       Options

	      bitrate bitrate
		     bitrate (1..1000000) required

	      samplepoint samplepoint
		     sample point (0.000..0.999)

	      loopback loopback
		     loop back CAN Messages (on|off)

	      listenonly listenonly
		     listen only mode (on|off)

	      triple triple
		     activate triple sampling (on|off)

	      oneshot oneshot
		     one shot mode (on|off)

	      berr berr
		     activate berr reporting (on|off)

KNOWN BUGS/LIMITATIONS
       The ifup and ifdown programs work with so-called "physical" interface names.  These  names
       are  assigned  to  hardware  by	the  kernel.  Unfortunately it can happen that the kernel
       assigns different physical interface 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.

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), ip(8), ifconfig(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/debian-refer-
       ence/ch05.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/net-
       work-interfaces.gz.

ifupdown				   5 April 2004 			    INTERFACES(5)
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