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Date:      Tue, 22 Jan 2002 11:24:12 +0000 (GMT)
From:      =?iso-8859-1?q?Gavin=20Kenny?= <gavinkenny@yahoo.co.uk>
To:        questions@freebsd.org
Subject:   Re: VPN with dynamic IP's
Message-ID:  <20020122112412.21323.qmail@web20008.mail.yahoo.com>
In-Reply-To: <ABDA876D71F9D211B39D0090274EA8E20917C3EE@Floyd.logica.co.uk>

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 > -----Original Message-----
> From: Wayne Pascoe [mailto:freebsd@molemanarmy.com]
> Sent: 21 January 2002 19:12
> To: freebsd-questions@freebsd.org
> Subject: VPN with dynamic IP's
> 
> 
> Hi all,
> 
> Quick question about building a VPN. We have the
> following
> situation. Our office machine (and firewall) have
> fixed IP
> addresses. We also have several staff who have ADSL
> connections at
> home with dynamic IP's.
> 
> Our current corporate firewall (Raptor) is
> apparantly unable to
> provide VPN services with dynamic IP addresses. This
> is what our ops
> people tell me.
> 
> Can IPSEC provide this kind of solution ? Shouldn't
> this be doable
> using the private keys to authenticate ?

I don't think it is doable just with IPSec as IPSec
uses IP addresses to identify packets and therefore
know what processing to do to them
(encrypt/decrypt)IPSec does not even think about keys
until it has identified a packet by it's IP address.
IKE the IPSec key management deamon (called racoon on
FreeBSD) does pass keys between hosts but I seem to
remember that it again uses IP addresses as the
initial means of working out if you are worth talking
to.

If you used a FreeBSD machine as your VPN gateway it
could be concievable to write a little script, where
your machine with a dynamic address could find out
it's IP address and then send this to the firewall as
a PGP protected email or something (ssh I guess, I've
no experience of this) the firewall would then decrypt
the new IP address using PGP and could then alter its
SA/SP tables accordingly, racoon would then be
automatically called when you first tried to connect
and a key exchange would happen and hey presto secure
comms.

hope this is usefull

cheers

Gavin

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