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.TH IFUPDOWN-MULTI-INTERFACES 5 "17 September 2013" "0.1.0" "File formats"
.SH NAME
ifupdown-multi-interfaces \- ifupdown-multi extension for the interfaces(5) file format
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.SH DESCRIPTION
.sp
\fI/etc/network/interfaces\fP contains network interface information for the
\fBifup\fP(8) and \fBifdown\fP(8) commands. This manpage describes the
\fBifupdown\-multi\fP extensions to the the standard \fBinterfaces\fP(5) file
format.
.sp
The \fBifupdown\-multi\fP extensions to \fBifupdown\fP integrate Linux\(aqs policy
routing based support for multiple default gateways on independent network
connections. These extensions can replace a typical shell script based approach
that directly invokes a sequence of \fBip\fP(8) commands for configuring
multiple uplinks with declarative syntax in the \fI/etc/network/interfaces\fP file.
.sp
\fBifupdown\-multi\fP records the policy information used to bring up each network
interface when \fBifup\fP(8) is run and removes the same policy routing
information when \fBifdown\fP(8) is run.
.SH IFACE OPTIONS
.sp
The standard \fBaddress\fP and \fBnetmask\fP options must be set for each
interface. The \fBgateway\fP option must \fINOT\fP be set.
.sp
The new \fBmulti_gateway\fP and \fBmulti_table\fP options must be set to configure
policy routing with \fBifupdown\-multi\fP\&.
.sp
Additionally, the \fBmulti_gateway_weight\fP and \fBmulti_preferred_prefixes\fP
options can be specified in order to control optional policy routing features.
.INDENT 0.0
.TP
.B \fBmulti_gateway\fP \fIaddress\fP
Default gateway for this interface. (Required.)
.TP
.B \fBmulti_table\fP \fIid\fP
Table identifier. This must be a numeric value, and each interface must have a
unique value. Recommended range: 1\-1000. (Required.)
.TP
.B \fBmulti_gateway_weight\fP \fIweight\fP
Set this gateway\(aqs weight. This value is directly passed as the \fIweight\fP
parameter to the \fInexthop\fP part of an \fBip\-route\fP(8) route object. Higher
values indicate higher relative bandwidth or quality. (Optional.)
.TP
.B \fBmulti_preferred_prefixes\fP \fIprefix\fP [\fIprefix\fP]...
Prefer this connection for the given prefixes. This option configures the
routing policy database using the \fBip\-rule\fP(8) command to use this
connection for the specified prefixes. (Optional.)
.UNINDENT
.SH EXAMPLES
.sp
The following example shows a basic configuration with two network interfaces.
\fIeth0\fP is on the 198.51.100.0/24 network, while \fIeth1\fP is on the 203.0.113.0/24
network. Each interface stanza has a "multi_gateway" option, as opposed to the
usual "gateway" option. Each interface stanza also needs a "multi_table" option,
whose parameter is a small, unique non\-negative integer.  (This number will be
used internally to uniquely identify an interface\-specific routing table.)
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
auto eth0
iface eth0 inet static
    address 198.51.100.123
    netmask 255.255.255.0
    multi_table 1
    multi_gateway 198.51.100.1

auto eth1
iface eth1 inet static
    address 203.0.113.234
    netmask 255.255.255.0
    multi_table 2
    multi_gateway 203.0.113.1
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
The following example shows a more complicated setup using optional
\fBifupdown\-multi\fP parameters. It is similar to the first example, but the
network connection on \fIeth0\fP is preferred for most connections, and several
network prefixes prefer to use one or the other network connection.
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
auto eth0
iface eth0 inet static
    address 198.51.100.123
    netmask 255.255.255.0
    multi_table 1
    multi_gateway 198.51.100.1
    multi_gateway_weight 5
    multi_preferred_prefixes 10.0.0.0/8

auto eth1
iface eth1 inet static
    address 203.0.113.234
    netmask 255.255.255.0
    multi_table 2
    multi_gateway 203.0.113.1
    multi_gateway_weight 1
    multi_preferred_prefixes 172.16.0.0/12 192.168.0.0/16
.ft P
.fi
.UNINDENT
.UNINDENT
.SH FILES
.INDENT 0.0
.TP
.B \fI/etc/network/interfaces\fP
System\-wide network interface configuration. See \fBinterfaces\fP(5).
.TP
.B \fI/run/network/ifupdown\-multi.*\fP
State information used by \fBifupdown\-multi\fP\&.
.UNINDENT
.SH SEE ALSO
.sp
\fBinterfaces\fP(5), \fBifup\fP(8), \fBip\fP(8), \fBip\-route\fP(8), \fBip\-rule\fP(8).
.INDENT 0.0
.TP
.B Linux Advanced Routing & Traffic Control HOWTO \-\- Chapter 4: Rules.
\fI\%http://www.tldp.org/HOWTO/Adv\-Routing\-HOWTO/lartc.rpdb.html\fP
.UNINDENT
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