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Date: Sat, 12 Sep 2009 15:09:13 +0200
From: Luigi Rizzo <rizzo@iet.unipi.it>
To: Cypher Wu <cypher.w@gmail.com>
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Cc: freebsd-ipfw@freebsd.org
Subject: Re: Transparent firewall & Dynamic rules
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On Sat, Sep 12, 2009 at 03:32:54PM +0800, Cypher Wu wrote:
> I want to build a transparent firewall based on IPFW. For static rules
> this is fine, but for dynamic rules, ipfw uses keepalive packet to
> avoid deleting a dynamic rule that both ends are still alive but don't
> issue any traffic for a long time. But this means the firewall should
> have it's own IPs and is not transparent anymore.

keepalives carry the addresses of the two endpoints,
the firewall is not visible.