ipv6 route ignores MTU.

[Zaphod Beeblebrox]

On Thu, Dec 13, 2012 at 2:31 PM, John-Mark Gurney <jmg at 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.