CentOS 7 NAT configuration

configure_nat_bridge.sh

#!/usr/bin/env bash
# In this configuration, there are two networks:
#   eth0 -> a "WAN" into the office network
#   eno1 -> a "LAN" of attached vendor hardware on network 192.168.0.0/24
#           this interface's IP is 192.168.0.1, and attached hardware use
#           that address as their GATEWAY.
​
WAN_INT="eth0"
LAN_INT="eno1"
LAN_NET="192.168.0.0/24"
​
# Enable IPv4 forwarding
echo "net.ipv4.ip_forward = 1" | sudo tee -a /etc/sysctl.d/99-ip-forwarding.conf
sudo sysctl -p --system
​
# Install and Configure IP Tables
sudo yum install -y iptables*
sudo iptables -P INPUT ACCEPT
sudo iptables -F INPUT
sudo iptables -P OUTPUT ACCEPT
sudo iptables -F OUTPUT
sudo iptables -P FORWARD DROP
sudo iptables -F FORWARD
sudo iptables -t nat -F
sudo iptables -A FORWARD -i ${WAN_INT} -o ${LAN_INT} -m state --state ESTABLISHED,RELATED -j ACCEPT
sudo iptables -A FORWARD -i ${LAN_INT} -o ${WAN_INT} -j ACCEPT
sudo iptables -t nat -A POSTROUTING -s ${LAN_NET} -o ${LAN_INT} -j MASQUERADE
sudo iptables-save > /etc/sysconfig/iptables
sudo systemctl restart iptables
sudo systemctl restart network

No guarantees this works as-is right now and you'll have to patch in your device interface names. This works sometimes.