Load Balance Within Two or More ISP Using Slackware

i've got this from the net.. not sure where did i found it.. its a couple years in my note since playing with slackware and it does really work.


====== START =======


#!/bin/bash
#
# bal_local Load-balance internet connection over two local links
#
# Version: 1.0.0 - Fri, Sep 26, 2008
#
# Author: Niels Horn
#


# Set devices:
DEV1=${1-eth0} # default eth0
DEV2=${2-ppp0} # default ppp0


# Get IP addresses of our devices:
ip1=`ifconfig $DEV1 | grep inet | awk '{ print $2 }' | awk -F: '{ print $2 }'`
ip2=`ifconfig $DEV2 | grep inet | awk '{ print $2 }' | awk -F: '{ print $2 }'`


# Get default gateway for our devices:
gw1=`route -n | grep $DEV1 | grep '^0.0.0.0' | awk '{ print $2 }'`
gw2=`route -n | grep $DEV2 | grep '^0.0.0.0' | awk '{ print $2 }'`


echo "$DEV1: IP=$ip1 GW=$gw1"
echo "$DEV2: IP=$ip2 GW=$gw2"


### Definition of routes ###


# Check if tables exists, if not -> create them:
if [ -z "`cat /etc/iproute2/rt_tables | grep '^251'`" ] ; then
echo "251 rt_dev1" >> /etc/iproute2/rt_tables
fi
if [ -z "`cat /etc/iproute2/rt_tables | grep '^252'`" ] ; then
echo "252 rt_dev2" >> /etc/iproute2/rt_tables
fi


# Define routing tables:
ip route add default via $gw1 table rt_dev1
ip route add default via $gw2 table rt_dev2


# Create rules:
ip rule add from $ip1 table rt_dev1
ip rule add from $ip2 table rt_dev2


# If we already have a 'nexthop' route, delete it:
if [ ! -z "`ip route show table main | grep 'nexthop'`" ] ; then
ip route del default scope global
fi


# Balance links based on routes:
ip route add default scope global nexthop via $gw1 dev $DEV1 weight 1 nexthop via $gw2 dev $DEV2 weight 1


# Flush cache table:
ip route flush cache


# All done..


chmod +x the script and call it with ./yourscript eth0 ppp0 after connected to the internet. change accordingly to fit your need such as adding more ISP