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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"  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-<&lt;option>&gt;.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 spell-
                     ing 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  <ajATazure.hum-
       bug.org.au>.    This   manpage   was   contributed   by    Joey    Hess
       <joeyATkitenet.net>.

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)