Provided by: ifupdown_0.7.47.2ubuntu4.5_amd64 
NAME
/etc/network/interfaces - network interface configuration for ifup and ifdown
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", "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/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.
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 virtual LAN interface. For example, interface
eth0.1 is a virtual interface 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 arguments) 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 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:/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 discarded.
When ifupdown is being called with the --all option, before doing anything 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 family.
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 spelling 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 commands 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 family.
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. Unfortunately it can happen that the kernel
assigns different physical interface 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.humbug.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.