Re: DMZ to DMT through ROUTER problem !

[Antony Stone <Antony@Soft-Solutions.co.uk>]

On Thursday 20 May 2004 12:18 pm, O-Zone wrote:

> i've a big problem. Here's a little diagram:
>
> [INTRANET 10.0.0.0/24]-------------+
>                                                       +--[ROUTER]--(NET)
> [DMZ SERVER A - 192.168.0.2]----+
> [DMZ SERVER B - 192.168.0.3]----+
>
> Each DMZ server is mapped to it's PUBLIC IP. For example:
>
> 151.8.47.A ----> 192.168.0.2
> 151.8.47.B ----> 192.168.0.3
>
> and all work perfectly !!!
>
> The problem is when, from 192.168.0.2, i try to connect to 151.08.47.B
> (trat's mapped to 192.168.0.3): packets die on ROUTER.

It's the reply packets which are the problem.

Think about a TCP connection:

1. SYN packet from 192.168.0.2 to 151.8.47.B goes to the firewall.
2. Firewall DNATs 151.8.47.B to 192.168.0.3
3. SYN packet goes from firewall to 192.168.0.3
4. 192.168.0.3 sends SYN-ACK to 192.168.0.2 on local net (not via firewall)
5. 192.168.0.2 wonders why it got a SYN-ACK from 192.168.0.3 when it sent the 
SYN to 151.8.47.B

http://www.netfilter.org/documentation/HOWTO/NAT-HOWTO-10.html

Regards,

Antony.

-- 
"The problem with television is that the people must sit and keep their eyes 
glued on a screen; the average American family hasn't time for it."

 - New York Times, following a demonstration at the 1939 World's Fair.

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