which iptables command to run firefox behind a linux router?

one of my PC is a linux router. its name is 'rato'. the ip adress of the router are :,,,,,
on this router, 'route' give:
[root@rato etc]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface   U     0      0        0 eth3   U     0      0        0 eth2   U     0      0        0 eth1   U     0      0        0 eth0   U     0      0        0 eth6         UG    0      0        0 eth0
on this router, 'iptables' give:
[root@rato etc]# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
[root@rato etc]#
on the router 'rato', I can run firefox and acces to internet thru adsl thru the net
I would like to be able to access to internet thru firefox on any pc of the net
what are the iptables commands to be able to run firefox from any pc of the
for instance, I want to run firefox on the ? which iptable should I type on the router?

Who is Participating?
You don't actually need to run iptables for you to browse the internet.
1. turn on ip_forwarding
2. set routes on your adsl router for subnets (,,,, via

All your traffic will go through RATO as it now acts as a router.

If you wish to setup iptables fIrewall, then I suggest you have a good read of the link above.

For a quick fix you can check out this sample iptables file and modify as required:

How do you actually exit your network to reach the internet ?
As all of your interfaces are (RFC1918), there is no internet connection.

All the same check the config file:

cd /etc/sysconfig/iptables
Actually I just noticed, your default gateway is !!!
Then you will probably need to check that ip_forwarding is turned on and also check the file I mentioned above.
Another thing will be routing back to your rato firewall, either on the router you will need to route the other subnets back or you will need to configure masquerading.
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gdmoAuthor Commented:
Yes, the gateway is a adsl modem-router. But, for some reasons, I want to use un linux router and not a adsl modem-router. The reasons are that I want to have separate subnets.
As far as I know, to configure masquerading, I will need to configure iptables on the 'rato' router. As I have not yet used iptables, I have not yet well understood iptables. I would like than somebody say which command iptables are to be used.
check out this link:

you will need to work out exactly what you want to do with the traffic and then apply it into a file.
If you want further information explain in detail what you want to achieve eg: source destination traffic flows, who sees who, etc..
gdmoAuthor Commented:
I know exactly the result that I expect to obtain. But, unfortunately, I do not know the iptables commands I must write to obtain what I want.  I just want that a pc under linux whom ip adress is could acces web by firefox.
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