Mac OS X 10.7, still no DHCPv6

Tore Anderson tore.anderson at
Sun Feb 27 17:41:34 CST 2011

* Owen DeLong

> On Feb 27, 2011, at 4:21 AM, Randy Bush wrote:
>> NOC: are you running a macintosh?
>> User: yes, how did you guess?
>> NOC: because it is broken.  get vista.
> While I'm as big a fan of IPv6 as anybody, I think in a comparison of
> relative brokenness, Mac comes out quite favorably compared to
> Vista in spite of their DHCPv6 deficiencies.

Absolutely not. Mac OS X does not do proper source address selection
according to RFC 3484. That makes it do things like preferring the use
of link-local IPv6 addresses when connecting to global dual-stacked
destinations, which of course won't work - as a result a 75 second long
timeout is incurred for every single outgoing TCP connection. Versions
earlier than 10.6.5, still in use by a considerable amount of users,
will also prefer the use of 6to4 to IPv4, again something which is
causing lots of brokenness. (Windows ICS is responsible for causing lots
of OS X hosts to have 6to4 addresses in the first place, though.)

OS X also has a bug that will make it interpret a router lifetime of 0
in a RA as infinite, causing more troubles when found behind IPv6 CE
routers using ULAs in compliance with I-D.ietf-v6ops-ipv6-cpe-router,
one example of which is the AVM FritzBox as far as I understand.

See also:

My guess is that about 70-80% of the users calling Randy and others to
report problems on «World IPv6 Day» will be running Mac OS X.

Ray: Do you know if RFC 3484 has been implemented in OS X 10.7?

Tore Anderson
Redpill Linpro AS -
Tel: +47 21 54 41 27

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