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Date: Thu, 14 Jul 2005 12:46:11 +0900
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From: gnn@freebsd.org
To: Jeremie Le Hen <jeremie@le-hen.org>
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References: <20050713130042.GV39292@obiwan.tataz.chchile.org>
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Cc: freebsd-net@freebsd.org
Subject: Re: Problem with Path MTU Discovery
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At Wed, 13 Jul 2005 15:00:42 +0200,
Jeremie Le Hen wrote:
> 
> Hi,
> 
> I set a gif(4)-based IPSec tunnel between my network and a friend's one.
> This works pretty well, except that Path MTU Discovery doesn't work.
> 
> Quick draw:
>           MTU: 1500       MTU:1280       MTU:1500
>     Comp1 --------- Gate1 -------- Gate2 -----+-- Comp2
>     RELENG_5        RELENG_4       RELENG_5   |   RELENG_5
>                                               |
>                                               +-- Comp3
>                                                   RELENG_5
> 

Can you look at the routing table for each of Comp1 and Comp2 and also
use the -W flag to show the path MTU?  If there is something wonky in
the routing table then TCP will not hear about the MTU change.

Thanks,
George