Re: DNAT and local hosts

[Ray Leach <spoons@rchq.co.za>]

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Pieter De Wit wrote:
> *BEEP* *BUZZ* I know - but it's for a closed source app that I need to do this - and it takes the address from the server, the protocol doesn't carry it it :)
> 
> 
> -----Original Message-----
> From: Jan Engelhardt [mailto:jengelh@linux01.gwdg.de]
> Sent: Mon 2007/05/07 18:01
> To: Pieter De Wit
> Cc: netfilter@lists.netfilter.org
> Subject: Re: DNAT and local hosts
>  
> 
> On May 7 2007 17:54, Pieter De Wit wrote:
>> Now, all connections are routed out via FW:ppp0 and at NAT'ed. There is
>> a rule that allows connections to ppp0 on port 1234 and DNAT's them to
>> C1. When C2 makes a connection to 1.2.3.4:1234 it fails with "Connection
>> refused" since there is no "server" listening on the firewall's
>> ppp0,port 1234.
> 
> *BEEP* *BUZZ* *ERROR*. You have a direct connection between C1 and C2.
> 
> 
> Jan

There is no routing between C1 and C2, so your firewall never sees the 
traffic between the 2.

Put C1 and C2 on two seperate physical networks and connect them through 
firewall to get routing to happen, then you can use iptables to do 
NATing between them.

Else put two interfaces into your firewall, give each interface an ip 
address in the same subnet, configure bridging between the two, put C1 
on the end of one interface and C2 on the other if, then look into ebtables.