Firewall with more than one External interface

Hi all,
i've a question about linux firewall, hope that here is a good place.
Sorry for my english.
My problema is this: i've one box with 4 NIC. Two nic are in INTERNAL
(secure) lan and the other two are in the External (insecure) lans.
The two external have connection with two different router of two
different Internet Service Provider. The two pubblic IP class
naturally are different.
The box works now with all two the providers, and i'm able to make
some NAT between one provider or the other.
The firewall is setup with FirewallBuilder.
Now happened that i MUST reconfigure all, and i start from a clean
FirewallBuilder setup.
So, only the IPTABLES configuration, from FirewallBuilder is change,
non network setup is change.
When i apply my new configuration, i'm able to make NAT only from one
of the two internet service provider (and the pubblic IP from this).
Naturally, the one that is specified like GATEWAY in /etc/sysconfig/
network file (Fedora Core 4). So, what i missed? What i forget? Where
i can specify that all two the provider can be a GATEWAY depending
from were the request arrives? ... why with the old FirewallBuilder
configuration works (naturally not maked by me) and now not works?
Thanks all.
Mauro.

On Jun 12, 2:03*pm, Mauroreg...@gmail.com wrote:
> Hi all,
> i've a question about linux firewall, hope that here is a good place.
> Sorry for my english.
> My problema is this: i've one box with 4 NIC. Two nic are in INTERNAL
> (secure) lan and the other two are in the External (insecure) lans.
> The two external have connection with two different router of two
> different Internet Service Provider. The two pubblic IP class
> naturally are different.
> The box works now with all two the providers, and i'm able to make
> some NAT between one provider or the other.
> The firewall is setup with FirewallBuilder.
> Now happened that i MUST reconfigure all, and i start from a clean
> FirewallBuilder setup.
> So, only the IPTABLES configuration, from FirewallBuilder is change,
> non network setup is change.
> When i apply my new configuration, i'm able to make NAT only from one
> of the two internet service provider (and the pubblic IP from this).
> Naturally, the one that is specified like GATEWAY in /etc/sysconfig/
> network file (Fedora Core 4). So, what i missed? What i forget? Where
> i can specify that all two the provider can be a GATEWAY depending
> from were the request arrives? ... why with the old FirewallBuilder
> configuration works (naturally not maked by me) and now not works?
> Thanks all.
> Mauro.

You will need a special rule to route based on source address. There
are two places you can put this rule. One is in the firewall itself,
to make sure it forwards a packet to the correct router based on the
source address. The other is in the two routers, to have each one
bounce a packet to the other router if it receives a packet from the
LAN with a source address assigned by the other provider.

DS

On Jun 12, 6:03 pm, Mauroreg...@gmail.com wrote:
> Hi all,

Hi pal,

Try to not crosspost.