Linux and ULA support and default route

[otroan at employees.org]

> On 14 Oct 2016, at 12:32, Gert Doering <gert at space.net> wrote:
> 
> Hi,
> 
> On Fri, Oct 14, 2016 at 12:00:04PM +0200, Holger Zuleger wrote:
>> Of course the default route should *not* be withdrawn.
>> The RA default router announcement says just, "Hey hosts, I'm the way
>> out of your local subnet", and not "Hey host, I have a upstream
>> connection to the rest of the internet".
> 
> If the router has no default route, it should not announce one - this
> is why PIO exists for more specific info.
> 
> Imagine a setup with *two* routers.  One of them has broken Internet,
> the other is working.  How can the hosts decide if both keep announcing
> themselves as "I can reach anything"?

in the general case the host still has to take the 'I can reach anything' announcement with a pinch of salt.
and it should be able to try both (or more) connections and react accordingly when one fails.
the first hop router has a very limited view of the end to end path.

cheers,
Ole