https://serverfault.com/questions/864760/iptables-bastion-network-with-acces-to-internet-how-to-set-up-rules
sysctl -w net.ipv4.ip_forward=1
export internet=enp2s0
export internal=enp3s0
iptables -A FORWARD -o $internet -j ACCEPT
iptables -A FORWARD -m state --state ESTABLISHED,RELATED -i $internet -j ACCEPT
iptables -t nat -A POSTROUTING -o $internet -j MASQUERADE
iptables -A FORWARD -o $internal -j ACCEPT
iptables -A FORWARD -m state --state ESTABLISHED,RELATED -i $internal -j ACCEPT
iptables -t nat -A POSTROUTING -o $internal -j MASQUERADE