Re: [homenet] draft-boutier-homenet-source-specific-routing-00

[Juliusz Chroboczek <[e-mail]>]

> > You're assuming that non-source-specific routers drop source-specific
> > routes, right?
> 
> Doesn't really matter, at least for the routes to the gateways.

Hmm...

Consider the following topology:


  -- A -- X -- B --
       \     /
        - Y -

A is announcing (::/0, alpha), B is announcing (::/0, beta).  X is
source-specific.  Y is a legacy router.

Suppose now that rather than dropping the source-specific routes, Y is
casting them into non-specific default routes, and that it has
selected A as its next hop for the default route.

Now X crashes:

  -- A         B --
       \     /
        - Y -

A's routing table is now just (::/0, alpha) and (::/0, ::/0), with the
latter pointing at Y.  But Y is still pointing its default route at A,
so you're in trouble.

If legacy routers just drop specific routes -- you get a blackhole
instead of a routing loop.

-- Juliusz