Re: Running code (Was: I-D Action: draft-ietf-6man-ipv6only-flag-03.txt)

[Brian Haberman <[e-mail]>]

Hi Bert,

On 10/26/18 8:05 PM, Manfredi (US), Albert E wrote:
> -----Original Message-----
> From: ipv6 <[e-mail]> On Behalf Of Simon Hobson
> 
>> You've missed the fact that most nodes these days will autoconfigure a link-local IPv4 address. So "no address = no protocol" doesn't work. "no address (other than link-local) = no protocol" doesn't work either as it would break any network using link-local addressing - they do exist.
> 
> No problem, right? With the IPv6-ony flag set, what would a host do? If it does autoconfigure an IPv4 address, maybe to talk to some old printer, it can do so also with the new heuristic. What the host will know is that it can’t route anything outside. There is nothing here that the flag changes. And besides, who knows what hosts will do when they receive that IPv6-onky flag. We are simply speculating. Whether the better heuristics, or this new flag, makes little difference.

I think your observation is key for everyone. The flag only indicates
that the router(s) will not route IPv4 off the link. There is nothing
stopping devices from using IPv4 locally on the link to communicate with
other such devices.

The same thing occurs today with devices using IPv6 link-locals on
IPv4-only links.

Brian