Shell script to quickly switch between real Internet connection (NAT) and simulated (INetSim)

net-config.sh

#!/bin/bash

case "$1" in
router)
	sysctl -w net.ipv4.ip_forward=1
	iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
	systemctl start dnsmasq.service
	;;
router-stop)
	sysctl -w net.ipv4.ip_forward=0
	iptables -t nat -D POSTROUTING -o eth0 -j MASQUERADE
	systemctl stop dnsmasq.service
	;;
inetsim)
	iptables -t nat -A PREROUTING -i eth1 -j REDIRECT
	inetsim
	iptables -t nat -D PREROUTING -i eth1 -j REDIRECT
	;;
*)
	echo "Usage: $0 {router|router-stop|inetsim}"
	;;
esac