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

[KORTA]

I made a picture
If a packet arrives from provider B, I want that the packet will be routed
by the same provider even if the default route is provider A.

You gave me the syntax to route from source address,
I just want to know if there is possible to route packets depends on which
interface they arrives.
Tx


-----Message d'origine-----
De : Oscar Mechanic [mailto:oscar at ufomechanic.net] 
Envoyé : samedi 14 octobre 2006 13:56
À : KORTA
Cc : lartc at mailman.ds9a.nl
Objet : Re: [LARTC] Problem with two providers:Need to route packets on the
interface on which they arrives.

There is a simple way a hard way to do this. You could use
connmark in iptables. And then use ip rule & routes to set
route based on that. As I am not going to replicate this to test
I wont try and guess commands.

Easiest configure 2 IP's on server.

DNAT like 
iptables -t nat -I PREROUTING 1 -i ethA -j DNAT --to-destination
<10.0.0.A> 
iptables -t nat -I PREROUTING 1 -i ethB -j DNAT --to-destination
<10.0.0.B>

ip rule add from 10.0.0.B lookup 120
ip route add default via <B ISP Address> table 120

Thats the easiest I can think of.



On Sat, 2006-10-14 at 13:10 +0200, 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.
> 
>  
> 
>  
> 
> 
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