[LARTC] Problem with two providers:Need to route packets on the interface on which they arrives.

[Alessandro Ren]

KORTA wrote:
>
> Hello,
>
>  
>
> i would like to know how to resolve a problem.
>
>  
>
> I have a debian router with 3 interfaces (LAN, and two internet 
> providers (Provider A, Provider B)).
>
>  
>
> The default route is configured to use the provider A
>
>  
>
> The problem is that,
>
> When an external connection arrives from provider B to an internal 
> server (with nat),  the packet is routed to the default route:
>
> I explain:
>
> -          A packet arrives from provider B in direction of a internal 
> server
>
> -          The router performs nat operation
>
> -          The internal server generates a response
>
> -          The router routes the packet on the interface Provider A
>
>  
>
> Consequently, The connection cannot been established
>
>  
>
> I want to know if its possible to configure my debian router to route 
> packets to the interface on which packet arrives. In the example, 
> packets should have been routed by the interface connected to provider B
>
>  
>
> If yes, do you know how to do that ?
>
>  
>
> Thanks.
>
>  
>

    I think tha CONNTRACK solves this problem for you, putting packets 
that comes in and out, using PREROUTING and POSTROUTING.
    []s.