iptables -t nat -A prerouting_wan -p tcp --dport 2221 -j DNAT --to 192.168.254.21:22
iptables        -A forwarding_wan -p tcp --dport 22 -d 192.168.254.21 -j ACCEPT



i tried:

iptables -t nat -A POSTROUTING -p tcp --dst 192.168.254.21 --dport 22 -j SNAT --to-source 192.168.254.1