how to actibe iptables NAT?

[flintlong]

I had build the iptables nat into my kernel in redhat 7.1 , and I wanna use the NAT to let internet user (192.168.1.1) can come into my WWW_server (128.0.2.38 in intranet and 192.168.1.38 as true IP address provided by ISP) by NAT , so i use the command :

/sbin/iptables -t nat -A PREROUTING -i eth0 -d 192.168.1.38 -j DNAT --to 128.0.2.38

but I cannot visit the www_server in 192.168.1.1 ?

so , should i do something before I used the command, just like I should use the command :
 echo 1 > /proc/sys/net/ipv4/ip_forward
to turn on IP forwarding
  thx for any help 

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