multi-ip-route

#!/bin/bash
#
# Author: Preston M. <pentie [at] gmail.com> 2012.09.01
#
# This script sets up route tables for each different interface
#   properly descriped in /etc/network/interfaces.
# Useful when the server has more than one IP in different subnets with 
#    different gateways
#
# Usage:
#   1. put this script under /etc/network/if-up.d , make sure excuatable
#   2. describe interfaces in /etc/network/interfaces, it's better 
#        static, dhcp mode not tested. 
#       
#   The script will not work if any of this OPTIONS missing:
#        address
#        gateway
#        network
#

if [[ "$MODE" != start || "$IFACE" == lo || "$ADDRFAM" != inet ]]; then
    exit 0
fi

export `ifquery $IFACE|sed 's/: /=/;s/[- ]/_/g'`

if [[ -z $address || -z $gateway || -z $network ]]; then
    logger "$0: RouteTable Network for dev $IFACE incomplete. add=$address gw=$gateway nw=$network"
    echo "$0: RouteTable Network for dev $IFACE incomplete. add=$address gw=$gateway nw=$network"
    exit 0;
fi

TABLENAME="table`echo $address|sed 's/\.//g'`"

isIDInRtTables () {
    for NUM in `sed -n 's/^\([0-9]\+\).\+/\1/p' /etc/iproute2/rt_tables`; do
        if [[ $1 -eq $NUM ]]; then
            return 0
        fi
    done

    return 1;
}

if ! grep -q $TABLENAME /etc/iproute2/rt_tables; then
    while true; do
        let ID=$RANDOM%250
        if ! isIDInRtTables $ID; then
            echo $ID $TABLENAME >> /etc/iproute2/rt_tables
            break
        fi
    done
fi


/sbin/ip route add $network dev $IFACE src $address table $TABLENAME || true
/sbin/ip route add default via $gateway table $TABLENAME || true
/sbin/ip rule add from $address table $TABLENAME || true

logger "$0: Setup Route table $TABLENAME for $IFACE with gateway $gateway ."