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Interfaces

Table of contents



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" and "allow-" stanzas".
  • 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/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 logical 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 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.


Parameters

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-<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:No value assigned/usr/sbin:No value assigned/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.

  • 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 spelling 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 leastime
        • Preferred lease time in hours (pump)
      • leasetime leasetime
        • Preferred lease time in seconds (dhcpcd)
      • vendor vendor
        • Vendor class identifier (dhcpcd)
      • client client_id
        • 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 commands 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.
  • 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 loopback Method This method may be used to define the IPv6 loopback interface.

  • 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 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


Examples

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 192.168.1.10
    netmask 255.255.255.0
    gateway 192.168.1.1
    network 192.168.1.0
    broadcast 192.168.1.255
    up flush-mail 
iface eth0-work inet dhcp 
iface eth1 inet dhcp


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