Date: Fri, 14 Dec 2012 01:05:39 -0500 From: Zaphod Beeblebrox <zbeeble@gmail.com> To: Zaphod Beeblebrox <zbeeble@gmail.com>, FreeBSD Net <freebsd-net@freebsd.org> Subject: Re: ipv6 route ignores MTU. Message-ID: <CACpH0Mdhp2_GJ8f7Op6%2BRsn%2BmiFfTgZQYeVQO0DLnMyDVsb7kA@mail.gmail.com> In-Reply-To: <20121213193151.GE1563@funkthat.com> References: <CACpH0MdbHa%2BeYoE2XuaXkSUMOvkhL9bQkhFOgTtj1gOzbacQaw@mail.gmail.com> <20121213193151.GE1563@funkthat.com>
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On Thu, Dec 13, 2012 at 2:31 PM, John-Mark Gurney <jmg@funkthat.com> wrote: > > The MTU in this case is set in the ifconfig_em0 rc.conf entry and the > > machine has been rebooted. > > Are you sure that the mtu is set before the ipv6 address is assigned > to the interface? The route inherits what ever MTU was on the interface > when the route was created... It will be clamped if it is lower, but > will not be increased... This is so you can set the MTU on a route > (say you have a broken low memory device that only accept 512 byte packets) > and it will stay the way you set it.. Ordinarily, I would expect that since the MTU setting is in the ifconfig_em0 configuration line, this was sufficient. However, I realize now that this is not the case. Putting the MTU into the ipv6_ifconfig line did the trick. This is a rather serious violation of POLA --- I would suggest that some thought should be given to how this is configured and documented.
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