interfaces - network interface configuration for ifupdown


      By  default,  ifupdown2.conf  sets  /etc/network/interfaces  as  the
      network  interface   configuration   file.    This   file   contains
      information for the ifup(8), ifdown(8) and ifquery(8) commands.

      This  is  where  you  configure  how your system is connected to the

      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",  "auto",   "allow-"  and
      "source" stanzas. Here is an example:

          auto lo eth0
          allow-hotplug eth1

          iface lo inet loopback

          source /etc/network/interfaces.d/bridges

          iface eth0 inet static
              up flush-mail

          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.

      Lines  beginning  with  "allow-" are  used  to  identify  interfaces
      that should  be  brought  up automatically  by  various  subsystems.
      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

      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.  Currently  only  supports absolute path

      iface is normally given a interface name  as  its  first  non-option

      The  interface  name  is  followed by the name of the address family
      that the interface uses. This will be "inet" for  TCP/IP  networking
      and inet6 for ipv6. Following that is the name of the method used to
      configure the interface.

      ifupdown supports iface stanzas without a family or a  method.  This
      enables  using  the same stanza for inet and inet6 family addresses.
      And the method defaults to "static"

      Additional interface options/attributes can be given  on  subsequent
      lines  in  the  iface stanza. These options come from addon modules.
      see ifupdown-addons-interfaces(5) for these options.

      example bridge interface with additional attributes  listed  in  the
      ifupdown-addons-interfaces(5) man page:

          auto br0
          iface br0
              address 2000:1000:1000:1000:3::5/128
              bridge-ports swp1 swp2 swp3
              bridge-stp on

      ifupdown  supports  python-mako  style  templates  in the interfaces
      file.  See examples section for details.

      See /usr/share/doc/python-ifupdown2/examples/ for interfaces(5) file
      examples and interfaces file generation scripts.


      Both  inet and inet6 address family interfaces can use the following
      methods (However they are not required):

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

      The static Method
             This method may be used to define  ethernet  interfaces  with
             statically allocated addresses.

      The dhcp Method
             This method may be used to obtain an address via DHCP.


      iface  sections for some interfaces like physical interfaces or vlan
      interfaces  in  dot  notation  (like  eth1.100)  are  understood  by
      ifupdown.   These  interfaces do not need an entry in the interfaces
      file if they are dependents of other interfaces and don't  need  any
      specific configurations like addresses etc.


      Sample /etc/network/interfaces file:

          auto lo
          iface lo
              address 2001:dee:eeee:1::4/128

          auto eth0
          iface eth0 inet dhcp

          auto eth1
          iface eth1 inet manual
              address 2001:dee:eeee:1::4/128

          # source files from a directory /etc/network/interfaces.d
          source /etc/network/interfaces.d/*

          # Using mako style templates
          % for v in [11,12]:
              auto vlan${v}
              iface vlan${v} inet static
                  address 10.20.${v}.3/24
          % endfor

      For additional syntax and examples see ifupdown-addons-interfaces(5)


      configuration    file    defined    in    ifupdown2.conf    (default


      ifupdown-addons-interfaces(5), ifup(8), ifquery(8), ifreload(8)


   Roopa Prabhu <>


   Copyright 2014 Cumulus Networks, Inc.  All rights reserved.


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.