Three gateways to the internet

three_gateways_to_internet

#The Lord is my Shepherd, I shall not want
#He makes me lie down in green pastures
#He leads me besides quiet waters

#!/bin/bash
#This file is to setup a load balancing across 3 gateways to the internet
#First make sure to add the lines
#echo 200 t1 >> /etc/iproute2/rt_tables
#echo 201 t2 >> /etc/iproute2/rt_tables
#echo 202 t3 >> /etc/iproute2/rt_tables

#These are the subnets that the gateways are on
$P1_NET=192.168.1.0/24
$P2_NET=192.168.2.0/24
$P3_NET=192.168.4.0/24

#These are the ethernet devices connected to the gateways
$IF1=eth0
$IF2=eth0
$IF3=eth0

#These are the IP addresses of the machine that this script is run on
$IP1=192.168.1.20
$IP2=192.168.2.18
$IP3=192.168.4.20

#These are the IP addresses of the gateways
$P1=192.168.1.1
$P2=192.168.2.1
$P3=192.168.4.1

ip route add $P1_NET dev $IF1 src $IP1 table t1
ip route add $P2_NET dev $IF2 src $IP2 table t2
ip route add $P3_NET dev $IF3 src $IP3 table t3

ip route add $P1_NET dev $IF1 src $IP1
ip route add $P2_NET dev $IF2 src $IP2
ip route add $P3_NET dev $IF3 src $IP3

ip rule add from $IP1 table t1
ip rule add from $IP2 table t2
ip rule add from $IP3 table t3

ip route add default scope global nexthop via $P1 dev $IF1 weight 1 \
	    nexthop via $P2 dev $IF2 weight 1 \
	    nexthop via $P3 dev $IF3 weight 1