kernel: nd6_setmtu0: new link MTU on ng29 (1218) is too small for IPv6

[Sami Halabi]

Hi,
i just tested the last log:
%tail /var/log/messages
Jan  3 23:21:50 mpd2 kernel: nd6_setmtu0: new link MTU on ng92 (1218) is
too small for IPv6
Jan  4 00:00:36 mpd2 kernel: nd6_setmtu0: new link MTU on ng105 (1218) is
too small for IPv6
Jan  4 00:34:48 mpd2 kernel: nd6_setmtu0: new link MTU on ng105 (1218) is
too small for IPv6
Jan  4 07:47:37 mpd2 kernel: nd6_setmtu0: new link MTU on ng100 (1218) is
too small for IPv6
Jan  4 08:31:55 mpd2 kernel: nd6_setmtu0: new link MTU on ng116 (1218) is
too small for IPv6
Jan  4 09:16:21 mpd2 kernel: nd6_setmtu0: new link MTU on ng123 (1218) is
too small for IPv6
Jan  4 12:55:32 mpd2 kernel: nd6_setmtu0: new link MTU on ng53 (1218) is
too small for IPv6
Jan  4 14:17:34 mpd2 kernel: nd6_setmtu0: new link MTU on ng120 (1218) is
too small for IPv6
%ifconfig ng120
ng120: flags=88d1<UP,POINTOPOINT,RUNNING,NOARP,SIMPLEX,MULTICAST> metric 0
mtu 1218
        inet 188.64.96.5 --> 188.64.102.171 netmask 0xffffffff

so MTU is indeed 1218

Sami

2012/1/4 Gleb Smirnoff <glebius at freebsd.org>

> 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.
>



-- 
Sami Halabi
Information Systems Engineer
NMS Projects Expert