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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 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",  "allow-"
       and "source" stanzas. Here is an example.
       auto eth0
       allow-hotplug eth1

       source interfaces.d/machine-dependent

       source-directory interfaces.d

       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 configuration 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.)

       Similarly,  "source-directory" keyword is used to source multiple files
       at once, without specifying them individually  or  using	 shell	globs.
       Additionally,  when  "source-directory" is used, names of the files are
       checked to match the following regular expression: ^[a-zA-Z0-9_-]+$. In
       other words, the names must consist entirely of ASCII upper- and lower-
       case letters, ASCII digits, ASCII underscores, and ASCII minus-hyphens.
       In the directory path, shell wildcards may be used as well.

       When  sourcing  files  or directories, if a path doesn't have a leading
       slash, it's considered relative to the directory containing the file in
       which  the  keyword  is	placed.	 In  the example above, if the file is
       located at /etc/network/interfaces, paths to  the  included  files  are
       understood to be under /etc/network.

       By  default,  on a freshly installed Debian system, the interfaces file
       includes a line to source /etc/network/interfaces.d directory.

       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.

VLAN AND BRIDGE INTERFACES
       To ease the configuration  of  VLAN  interfaces,	 interfaces  having  .
       (full  stop character) in the name are configured as 802.1q tagged vir‐
       tual LAN interface. For example, interface eth0.1 is a  virtual	inter‐
       face having eth0 as physical link, with VLAN ID 1.

       For  compatibility with bridge-utils package, if bridge_ports option is
       specified, VLAN interface configuration is not performed.

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 them with "|| 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-<option>.d/ the scripts in which are run (with no argu‐
       ments)  using  run-parts(8) after the option itself has been processed.
       Please note that as post-up and pre-down are aliases, no files  in  the
       corresponding  directories  are	processed.  Please use if-up.d and if-
       down.d directories instead.

       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.

       When ifupdown is being called with the --all option, before doing  any‐
       thing  to  interfaces,  if  calls all the hook scripts (pre-up or down)
       with IFACE set to "--all", LOGICAL set to the current value of  --allow
       parameter   (or	 "auto"	  if   it's   not   set),  ADDRFAM="meta"  and
       METHOD="none".  After all the interfaces have been brought up or	 taken
       down, the appropriate scripts (up or post-down) are executed.

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/netmask) required

	      netmask mask
		     Netmask (dotted quad or CIDR)

	      broadcast broadcast_address
		     Broadcast	address	 (dotted quad, + or -). Default value:
		     "+"

	      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 spell‐
		     ing of "point-to".

	      hwaddress address
		     Link local address.

	      mtu size
		     MTU size

	      scope  Address  validity	scope.	Possible values: global, link,
		     host

   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

	      hwaddress address
		     Link local address.

	      mtu size
		     MTU size

   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)

	      metric metric
		     Metric for added routes (dhclient)

	      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  com‐
       mands 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/wvdial.conf).

   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  colloquially  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  fam‐
       ily.

   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 stateless DHCPv6
       support	is turned on, then additional network configuration parameters
       such as DNS and NTP servers will	 be  retrieved	from  a	 DHCP  server.
       Please  note  that  on  ifdown,	the lease is not currently released (a
       known bug).

       Options

	      privext int
		     Privacy extensions (RFC4941) (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/netmask) required

	      netmask mask
		     Netmask (number of bits, eg 64)

	      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).
		     Default value: "0"

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

	      scope  Address  validity	scope.	Possible values: global, site,
		     link, host

	      preferred-lifetime int
		     Time that address remains preferred

	      dad-attempts
		     Number of attempts to settle DAD (0 to disable).  Default
		     value: "60"

	      dad-interval
		     DAD  state	 polling  interval  in seconds. Default value:
		     "0.1"

   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

	      hwaddress address
		     Hardware address

	      mtu size
		     MTU size

   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

	      accept_ra int
		     Accept  router  advertisements  (0=off,  1=on).   Default
		     value: "0"

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

   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)

	      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.   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.

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

SEE ALSO
       ifup(8), ip(8), ifconfig(8), run-parts(8), resolvconf(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-reference/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/network-interfaces.gz.

ifupdown			 5 April 2004			 INTERFACES(5)
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