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