interfaces

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.

EXAMPLE
       The following  example  configures  two  network  interfaces:  eth0  is
       brought  up at boot, and uses DHCP for IPv4 and SLAAC for IPv6, whereas
       eth1 is brought up whenever the network hardware is  detected,  and  is
       configured with static IPv4 and IPv6 addresses.
       auto eth0
       allow-hotplug eth1

       iface eth0 inet dhcp

       iface eth0 inet6 auto

       iface eth1 inet static
            address 192.168.1.2/24
            gateway 192.168.1.1

       iface eth1 inet6 static
            address fec0:0:0:1::2/64
            gateway fec0:0:0:1::1

FILE FORMAT
       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-",
       "source" and "source-directory" stanzas. These  will  be  described  in
       more detail in the following sections.

INTERFACE SELECTION
       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  also  used by the system boot scripts, so interfaces marked
       "auto" are brought up at boot time.)  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.   (Interfaces
       marked "allow-hotplug" are brought up when udev detects them.  This can
       either be during boot if the interface is  already  present,  or  at  a
       later  time,  for  example when plugging in a USB network card.  Please
       note that this does not have anything to do with  detecting  a  network
       cable being plugged in.)

       Lines  beginning  with  "no-auto-down"  are used to identify interfaces
       that should not be brought down by the command "ifdown  -a".  Its  main
       use  is  to  prevent an interface from being brought down during system
       shutdown time, for example if the root filesystem is a network filesys-
       tem  and the interface should stay up until the very end. Note that you
       can still bring down the interface by  specifying  the  interface  name
       explicitly.

       Lines  beginning  with "no-scripts" are used to identify interfaces for
       which scripts in /etc/network/if-*.d/ should  not  be  run  when  those
       interfaces are brought up or down.

INCLUDING OTHER FILES
       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.

       Currently, "source-directory" isn't supported  by  network-manager  and
       guessnet.

       By  default,  on a freshly installed Debian system, the interfaces file
       includes a line to source files in the /etc/network/interfaces.d direc-
       tory.

MAPPINGS
       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.

INTERFACE DEFINITIONS
       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.)  A list of packages providing additional options is mentioned
       in the section "OPTIONS PROVIDED BY OTHER PACKAGE".

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

       Multiple "iface" stanzas can be given for the same interface, in  which
       case  all  of  the  configured addresses and options for that interface
       will be applied when bringing up that interface.   This  is  useful  to
       configure  both IPv4 and IPv6 addresses on the same interface (although
       if no inet6 stanza is present, the kernel will normally  still  perform
       stateless  address  autoconfiguration  if there is an IPv6 route adver-
       tisement daemon on the network). It can also be used to configure  mul-
       tiple addresses of the same type on a single interface.

INTERFACE TEMPLATES
       It is possible to define interface definition templates and extend them
       using the inherits keyword:

       iface ethernet inet static
            mtu 1500
            hwaddress 11:22:33:44:55:66

       iface eth0 inet static inherits ethernet
            address 192.168.1.2/24

       This may be useful to separate link-level settings shared  by  multiple
       interfaces  from,  for  example,  IP address settings specific to every
       interface.

VLAN 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.

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.

       description name
              Alias interface by name

       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  The physical name of the interface being processed,  or  "--all"
              (see below).

       LOGICAL
              The  logical  name  of  the interface being processed, or "auto"
              (see below).

       ADDRFAM
              The address family of the interface, or "meta" (see below).

       METHOD The method of the  interface  (e.g.,  static),  or  "none"  (see
              below).

       CLASS  The  class of interfaces being processed.  This is a copy of the
              value given to the --allow option when running ifup  or  ifdown,
              otherwise it is set to "auto" when the --all option is used.

       CLASS  The  class of interfaces being processed.  This is a copy of the
              value given to the --allow option when running ifup  or  ifdown,
              otherwise it is set to "auto" when the --all option is used.

       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.

OPTIONS PROVIDED BY OTHER PACKAGES
       This  manual  page  documents the configuration options provided by the
       ifupdown package.  However,  other  packages  can  make  other  options
       available  for use in /etc/network/interfaces.  Here is a list of pack-
       ages that provide such extensions:

       arping, avahi-autoipd, avahi-daemon, bind9, bridge-utils, clamav-fresh-
       clam,  controlaula,  epoptes-client,  ethtool,  guidedog, hostap-utils,
       hostapd, htpdate, ifenslave, ifmetric, ifupdown-extra,  ifupdown-multi,
       ifupdown-scripts-zg2,  initscripts, isatapd, linux-wlan-ng, lprng, mac-
       changer, miredo, nslcd, ntpdate, openntpd, openresolv,  openssh-server,
       openvpn, openvswitch-switch, postfix, resolvconf, sendmail-base, shore-
       wall-init, slrn, slrnpull,  tinc,  ucarp,  uml-utilities,  uruk,  vde2,
       vlan,  vzctl,  whereami, wide-dhcpv6-client, wireless-tools, wpasuppli-
       cant.

       Please consult the documentation  of  those  packages  for  information
       about how they extend ifupdown.

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 or "random".

              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 or "random".

              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)

              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

              metric metric
                     Routing metric for default gateway (integer)

              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)

              accept_ra int
                     Accept router advertisements (0=off, 1=on,  2=on+forward-
                     ing). Default value: "2"

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

              request_prefix int
                     Request a prefix through DHCPv6 Prefix Delegation (0=off,
                     1=on). Default value: "0"

              ll-attempts
                     Number of attempts to  wait  for  a  link-local  address.
                     Default value: "60"

              ll-interval
                     Link-local  address  polling interval in seconds. Default
                     value: "0.1"

   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)

              metric metric
                     Routing metric for default gateway (integer)

              gateway address
                     Default gateway (colon delimited)

              media type
                     Medium type, driver dependent

              hwaddress address
                     Hardware address or "random"

              mtu size
                     MTU size

              accept_ra int
                     Accept router advertisements (0=off, 1=on,  2=on+forward-
                     ing)

              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 DAD).
                     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 or "random"

              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 or "random"

              accept_ra int
                     Accept  router advertisements (0=off, 1=on, 2=on+forward-
                     ing). Default value: "1"

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

              request_prefix int
                     Request a prefix through DHCPv6 Prefix Delegation (0=off,
                     1=on). Default value: "0"

              ll-attempts
                     Number  of  attempts  to  wait  for a link-local address.
                     Default value: "60"

              ll-interval
                     Link-local address polling interval in  seconds.  Default
                     value: "0.1"

   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)

              metric metric
                     Routing metric for default gateway (integer)

              gateway address
                     Default gateway (colon delimited)

              ttl time
                     TTL setting

              mtu size
                     MTU size

              preferred-lifetime int
                     Time that address remains preferred

   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

              metric metric
                     Routing metric for default gateway (integer)

              ttl time
                     TTL setting

              mtu size
                     MTU size

              preferred-lifetime int
                     Time that address remains preferred

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                          4 June 2016                    INTERFACES(5)
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