Iptable for nat assistance

[Kihara Muriithi]

Hi all,
 I have been attempting to use iptables to NAT internal IPs to an external
IP without success. I have experience with iptables, but mainly on how to
close or open specific ports. Nat has proved a little challenging and thats
why i am seeking assistance.
 Lets say I have an internal IPs as 10.0.0.0/24 and need all those IP natted
to an external IP 192.168.2.1. This is what I have attempted in my quest to
find a solution.
/sbin/iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to 192.168.2.1

when I check the firewall status, I notice this table insertion
Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination
SNAT       all  --  0.0.0.0/0            0.0.0.0/0           to:192.168.2.1

 To be frank, I expected 192.168.2.1 to be the destination. The way the
details are presented is confusing, IMO. Whats however puzzling is this
command is rejected when I attempt to make it persistant as seen below.
vi /etec/sysconfig/iptables
Just before the line below, I inserted the second command
REJECT     all  --  0.0.0.0/0            0.0.0.0/0           reject-with
icmp-host-prohibited
-A POSTROUTING -o eth0 -j SNAT --to 192.168.2.1

This however don't work as iptable throws an error message and fails to come
up.
Now the question is, what is the proper way of doing a nat throw a linux
box? I have enabled IP forwarding by the way.

Thanks in advance
William
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