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Date: Wed, 4 Jan 2012 16:01:50 +0400
From: Gleb Smirnoff <glebius@FreeBSD.org>
To: Sami Halabi <sodynet1@gmail.com>
Message-ID: <20120104120150.GG34721@FreeBSD.org>
References: <CAEW+ogbY_ARtc4mVDQHpYPKgaLWHj64EhmFrQDNXuMcbn5Kz8Q@mail.gmail.com>
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User-Agent: Mutt/1.5.21 (2010-09-15)
Cc: freebsd-net@FreeBSD.org
Subject: Re: kernel: nd6_setmtu0: new link MTU on ng29 (1218) is too small
 for IPv6
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On Wed, Jan 04, 2012 at 12:59:18PM +0200, Sami Halabi wrote:
S> I'm using a FreeBSD8.2-R-p5 in conjunction with MPD5.5 port for creating
S> pptp/l2tp tunnels.
S> 
S> I'm using MPPC (Compression & Encryption), my current onfiguration i use
S> only IPv4.
S> 
S> I keep getting in the logs the following:
S> Jan  4 08:31:55 mpd2 kernel: nd6_setmtu0: new link MTU on ng116 (1218) is
S> too small for IPv6
S> Jan  4 09:16:21 mpd2 kernel: nd6_setmtu0: new link MTU on ng123 (1218) is
S> too small for IPv6
S> Jan  4 12:55:32 mpd2 kernel: nd6_setmtu0: new link MTU on ng53 (1218) is
S> too small for IPv6
S> 
S> although the NG tunnels don't negotiate IPv6.
S> 
S> a close look to the MPD log i see that this happens for connections that
S> set MRU/MTU 1400.
S> 
S> I talked to MPD developer (Alexander Motin) and this isn't a MPD problem,
S> rather than a kernel issue as the logs say.

Message is logged by kernel, but MTU is set by userland. Can you check
value of MTU with ifconfig, looking at an interface from most recent
discussed message? Is it really 1218?

-- 
Totus tuus, Glebius.