From mboxrd@z Thu Jan  1 00:00:00 1970
From: Antony Stone <Antony@Soft-Solutions.co.uk>
Subject: Re: How to drop/reject packets amongst LAN clients?
Date: Mon, 10 May 2004 17:43:54 +0100
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On Monday 10 May 2004 5:23 pm, michael@floog.net wrote:

> The LAN currently has 5 computers connected to it with static IP
> addresses:
>
> 192.168.1.2
> 192.168.1.3
> 192.168.1.4
> 192.168.1.5
> 192.168.1.6
>
> I will be adding 3 more machines with with static IP addresses:
>
> 192.168.1.7
> 192.168.1.8
> 192.168.1.9
>
> Issue:
>
> *.9 needs to remain accessible from *.7 and *.8; however, I need to
> restrict any connection or accessibility to *.9 from *.2 - *.6.

Netfilter (on the gateway router) is no use to you here, because packets 
between machines on the same subnet do not go through the router - they just 
talk to each other directly across your hub / switch.

Install netfilter on 192.168.1.9 and put rules in the INPUT chain:

iptables -A INPUT -A INPUT -s 192.168.1.7 -j ACCEPT
iptables -A INPUT -A INPUT -s 192.168.1.0/29 -j DROP

Regards,

Antony.

-- 
The idea that Bill Gates appeared like a knight in shining armour to lead all 
customers out of a mire of technological chaos neatly ignores the fact that 
it was he who, by peddling second-rate technology, led them into it in the 
first place.

 - Douglas Adams in The Guardian, 25th August 1995

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