iptables

https://blog.51cto.com/45545613/2083366

iptables -t nat -A POSTROUTING -s 172.21.6.231 -d 192.169.0.0/16 -o tunl0 -j MASQUERADE

iptables -t nat -A OUTPUT -d 133.64.36.129 -p tcp --dport 21 -j DNAT --to-destination 192.168.1.60