interesting about OSX, NAT64 prefix discovery

[Mikael Abrahamsson]

On Mon, 14 Oct 2013, Gert Doering wrote:

> Hi,
>
> On Mon, Oct 14, 2013 at 08:30:05AM +0200, Mikael Abrahamsson wrote:
>> Well, I don't *know* this is what was happening, but I see no other
>> mechanism that would explain the behaviour I was seeing. Anyone else seen
>> this or know more?
>
> My guess would be more like "resolver queries for IPv4 and IPv6.  IPv4 is
> serviced from /etc/hosts, while IPv6 is serviced from DNS = DNS64".

Nope, there were no DNS queries on the wire for this host at all.

SSH would try to connect to the IPv4 address, fail, then would connect to 
the NAT64 prefixed IPv4 address. So I'd say that when there was an entry 
in /etc/hosts, no DNS queries were done at all for this name.

> An IPv4-only entry in /etc/hosts will not result in "IPv6 resolver lookups
> will return NXDOMAIN".

This magic only seems to kick in when there is no real IPv4 connectivity 
at all. I encourage others to verify what I saw!

-- 
Mikael Abrahamsson    email: swmike at swm.pp.se