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Date:      Sat, 23 Jan 2010 13:03:49 -0500
From:      Nat Howard <freebsd-stable@track.pupworks.com>
To:        "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net>
Cc:        freebsd-stable@freebsd.org
Subject:   Re: IPSec NAT-T in transport mode
Message-ID:  <54E2892F-3F65-473E-9660-D2E8276E631B@track.pupworks.com>
In-Reply-To: <20100123100713.X50938@maildrop.int.zabbadoz.net>
References:  <B0B23035-26CD-45AE-96A0-D16957412C70@track.pupworks.com> <20100123100713.X50938@maildrop.int.zabbadoz.net>

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Much obliged for the answer, Bjoern, but I don't follow your logic --=20
If the NAT-T implementation on the L2TP Server (a freebsd box) is =
broken, wouldn't it be the one generating things with the wrong =
checksum?   If that's so, then surely=20
the point "A" wouldn't record seeing any incoming checksum errors, as =
they would all be outgoing packets, correct?  =20

Thanks for helping to shed light on this puzzle!



On Jan 23, 2010, at 5:09 AM, Bjoern A. Zeeb wrote:

> On Fri, 22 Jan 2010, Nat Howard wrote:
>=20
>> I'm very interested in this problem -- I want to run an L2TP server =
myself.   Is anyone actually working on this?  I might be able to chip =
in a few bucks...
>>=20
>> But I'm not seeing bad checksums.   Here's my setup:
>>=20
>>=20
>> L2tp server  A<---------------->B  Freebsd NAT box C =
<-----------internal network----------->D my mac
>>=20
>> Where should I be seeing the bad checksums?  A, B, C, or D?
>>=20
>>=20
>> Looking only at B, I don't see any bad udp checksums, but I'm seeing =
a bunch of these (IP numbers changed to bracketed names):
>=20
> This doesn't say if you are using IPsec but I will asume so, that
> would mean that you D "my mac" would initiate the connection and
> the A node "L2tp server" would then be the other end.  If that's a
> FreeBSD box as well, you should check statistics there.  The NAT
> gateway in between has nothing to do with this, only the IPsec ends.
>=20
> /bz
>=20
> --=20
> Bjoern A. Zeeb         It will not break if you know what you are =
doing.




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