Load balance 2 WAN links BASH script

BASH script to load balance 2 WAN links.

#!/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

if [ -z "`cat /etc/iproute2/rt_tables | grep '^252'`" ] ; then

echo "252 rt_dev2" >> /etc/iproute2/rt_tables

# 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

# 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...

To use the script, copy it to /usr/local/bin, make it executable with 'chmod +x' and call it with:

bal_local