Iptables NAT Forward Rules

#!/bin/bash
# Script para configurar reglas NAT iptables (configurarlo como router)

# VARIABLES
WAN=enp0s3
LAN=enp0s8
IPT=/sbin/iptables

if [ "$EUID" -ne 0 ]
  then echo "Please run as root"
  exit
fi

# Flush and delete all nat and  mangle #
$IPT -F
$IPT -X
$IPT -t nat -F
$IPT -t nat -X
$IPT -t mangle -F
$IPT -t mangle -X
$IPT -t raw -F
$IPT -t raw -X

echo 1 > /proc/sys/net/ipv4/ip_forward
$IPT -t nat -P POSTROUTING ACCEPT
$IPT -t nat -P PREROUTING ACCEPT
# Indicamos la interfaz con la que hacemos NAT expecificando las subredes
$IPT -t nat -A POSTROUTING -s 192.168.128.0/24 -o $WAN -j MASQUERADE

# Habilitar reenvío de interfaz LAN a WAN y viceversa
$IPT -A FORWARD -i $LAN -o $WAN -j ACCEPT
$IPT -A FORWARD -i $WAN -o $LAN -j ACCEPT

# Permitir las conexiones a la interfaz LAN desde su subred
$IPT -A INPUT -i $LAN -j ACCEPT
# Permitir SSH desde HOST Anfitrión WINDOWS a interfaz WAN
$IPT -A INPUT -i $WAN -p tcp -m state --state NEW --dport 22 -j ACCEPT