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Date:      Mon, 17 Sep 2001 13:49:33 +0200 (CEST)
From:      =?iso-8859-1?q?m=20p?= <sumirati@yahoo.de>
To:        brainheap@chat.ru
Cc:        freebsd-questions@freebsd.org
Subject:   Re: tiny question configuring ipfw
Message-ID:  <20010917114933.62086.qmail@web13307.mail.yahoo.com>

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> 
> Hi everybody!
> 
> I've read in ipfw man pages i can filter not only using ip-address but
> ports as well.
> Even though there's no example of such feature.
> 
> I'm curious how to write a rule to deny ip to some ip-address except for
> a single port?
> 
> Alex
> 

Hi Alex,

i don't know how to write one rule to serve your purpose. However, I know 2
rules which will do it :)

ipfw add allow log tcp from e.f.g.h to a.b.c.d 1 out via fxp0
ipfw add deny log ip from any to any 

a.b.c.d MAY be
- a single host (1.2.3.4)
- a network (1.2.3.0/24)
- a hostname (www.abc.com)
1 is the port number you want to have your clients access to.

e.f.g.h SHOULD be your IP address. 

"out" was applied because you mentioned ".. to some ip-address except for .."
and replace the interface over which the data goes out.

BUT: Take a look at /etc/rc.firewall. There are some very good hints against
spoofing and giving you a general idea how to write a ruleSET. A single rule
would not help you to protect your network properly.

Hope that helps

Marc

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