Linux and ULA support and default route

[Brian E Carpenter]

On 14/10/2016 23:32, Gert Doering 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 Of course the default route should *not* be withdrawn.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"?

Correct. When there's only one router, it doesn't matter too much (no default
route gives a prompt fail and a broken default route turns the Internet
into a black hole). But when there are multiple exits...

I really should have figured this out without help. S***, it's exactly the
problem that https://tools.ietf.org/html/draft-ietf-6man-multi-homed-host
is aimed at.

    Brian