Simple DNAT function

makednat() {
[ "$#" != "3" ] && return 1
iptables -t nat -I PREROUTING -p tcp --dport $1 -j DNAT --to-dest $2:$3
iptables -I FORWARD -s $2 -j ACCEPT
iptables -I FORWARD -d $2 -j ACCEPT
}

makednat 8686 10.80.140.1 22 #desktop