Configuration of NAT

[edwardspl ita org mo]

Dear All,

If all of service ( include Firewall ) in the same server, and the 
server use Private IP and connection with Router / HUB...
Then, how to define the NAT ( iptable function ) to transfer the IP 
Address ( Public <-> Private ) and auto assign the IP range for Client 
PCs ( LAN users ) ?
Is there an simple sample for reference ?

eg :
For Public IP ( from ISP ) :
IP range : 202.175.123.123 ~ 202.175.123.129 ( I want to assign IP 123 
for the Server first )
subnet mask : 255.255.255.240
Router IP : 202.175.123.128

For Private IP ( All of Server under LAN environment ) :
IP :  192.168.0.1 ( I want to tranfer to 202.175.123.123 )
subnet mask : 255.255.255.0 ( I want to tranfer to 255.255.255.240 )
Router IP : 192.168.0.254 ( I want to tranfer to 202.175.123.128 )

For Client IP ( via NAT + DHCP of the Server ) :
Ip : 192.168.1.1 ~ 192.168.1.50

Edward.