Firewall with more than one External interface - Networking

This is a discussion on Firewall with more than one External interface - Networking ; 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 ...

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Thread: Firewall with more than one External interface

  1. 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.

  2. Re: Firewall with more than one External interface

    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

  3. Re: Firewall with more than one External interface

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


    Hi pal,

    Try to not crosspost.




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