Create a multi-homed linux load balancer with two internet connections and one LAN connection

With the assistance of a few friends helping me research this, I was FINALLY able to get it working.

Had to run this script in order to properly forward TCP/IP traffic:

#!/bin/sh

PATH=/usr/sbin:/sbin:/bin:/usr/bin

# Primary Connection - 2085426230
   IF1=eth0
   IP1=172.16.0.2
    P1=172.16.0.1
P1_NET=172.16.0.0

# Secondary Connection - 2085420213
   IF2=eth1
   IP2=172.16.1.2
    P2=172.16.1.1
P2_NET=172.16.1.0

# Local Network
   IF3=eth2
   IP3=172.16.2.2
    P3=172.16.2.1
P3_NET=172.16.2.0

T1=WAN1
T2=WAN2

# delete all existing rules.
iptables -F
iptables -t nat -F
iptables -t mangle -F
iptables -X

# Always accept loopback and WAN traffic
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -i ${IF1} -j ACCEPT

# Allow established connections, and those not coming from the outside
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD -i ${IF1} -o ${IF3} -m state --state ESTABLISHED,RELATED -j ACCEPT

# Allow outgoing connections from the LAN side.
iptables -A FORWARD -i ${IF3} -o ${IF1} -j ACCEPT

# Masquerade.
iptables -t nat -A POSTROUTING -o ${IF1} -j MASQUERADE

# Enable routing.
echo 1 > /proc/sys/net/ipv4/ip_forward

Then I installed Net-ISP-Balance. Once the scripts ran and installed, I went to WhatsMyIP twice and sure enough, both interfaces are routing traffic as whatsmyip showed both IP addresses after I hit the refresh.

DISCLAIMER This worked for my particular network layout, configuration and settings. Your results may vary.