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Date:      Fri, 2 Nov 2001 11:44:52 -0800
From:      "Crist J. Clark" <cristjc@earthlink.net>
To:        John Massier <j_massier@hotmail.com>
Cc:        ipfw@FreeBSD.ORG
Subject:   Re: IN/OUT
Message-ID:  <20011102114452.M4360@blossom.cjclark.org>
In-Reply-To: <F11RnMbzrlRK8Nn97Yr000199b1@hotmail.com>; from j_massier@hotmail.com on Fri, Nov 02, 2001 at 05:44:42PM +0100
References:  <F11RnMbzrlRK8Nn97Yr000199b1@hotmail.com>

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On Fri, Nov 02, 2001 at 05:44:42PM +0100, John Massier wrote:
> Hi, Im a newbie in IPFW and im a bit confused with something.
> 
> I cant see the difference when you add a new rule between using <from 
> source to destination> to imply the way of the packet and using in/out.
> 
> Whats the real use of in/out?? Does this way imply direction?? Or in/out 
> are only used for specify interfaces??

In a typical firewall when a packet passes through we have a situation
like,

  wire ----> firewall ----> wire
        in            out

Where "in" and "out" are marked appropriately. Note that I have _not_
specified internal or external interfaces of the firewall. Generally,
"in" indicates the packet has just been received by the machine from
the network, and "out" means that the packet is about to be put out
onto the wire.
-- 
Crist J. Clark                     |     cjclark@alum.mit.edu
                                   |     cjclark@jhu.edu
http://people.freebsd.org/~cjc/    |     cjc@freebsd.org

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