Re: dual stack & IPv6 on by default

[Tim Chown <tjc@ecs.soton.ac.uk>]

On Mon, Mar 17, 2003 at 08:37:46PM -0800, Fred L. Templin wrote:
> I'm just dropping into this thread, and maybe this idea has already come up.
> But, when the DNS returns both A and AAAA records for a destination and
> when there is no v6 route, why can't the source just do automatic v6-in-v4
> tunneling using an address from an AAAA record as the v6dst and an address
> from an A record as the v4dst? Gives you a decision tree of sorts, i.e.:

In principle reasonable, but many things may still cause failure, e.g.
- the tunnelling fails due to firewall blocks
- the IPv4 connectivity is down
- the A and AAAA records may point to different hosts

Tim