Re: dual stack & IPv6 on by default

[Erik Nordmark <Erik.Nordmark@sun.com>]

> > A possible way to approach this problem would be to make
> > the choice between A and AAAA be a function of whether there
> > is one or more IPv6 route off-link (or at least one IPv6 router sending RAs).
> 
> Note this cuts both ways.  I've been in dual-protocol networks where IPv4
> has been down and IPv6 up, so we ought to consider the general case of
> availability of connectivity off-link for either protocol.

Good point and I agree in principle.
But the rules for detecting the lack of connectivity are likely to
be different in the IPv6 and IPv4 cases.
In IPv6 either RAs or some routing protocol provides routes to the node.
Thus the existence of (non manually configured) off-link routes indicate
the at least the first hop IPv6 routing is working.
In IPv4 in addition to dynamic schemes, the DHCP server can hand out a default 
route. But that router itself might not be working. Thus would it make sense
to be more "suspecious" about IPv4 default routes than in the IPv6 case
somehow?

  Erik