nanog mailing list archives

Re: Mac OS X 10.7, still no DHCPv6


From: Karl Auer <kauer () biplane com au>
Date: Mon, 28 Feb 2011 18:49:36 +1100

On Mon, 2011-02-28 at 12:57 +1100, Mark Andrews wrote:
Except in the senarios being described they are also blocking the
other addresses.  I would also think setting the "M" bit would
prelude the host from generating such addresses as they are unmanaged.

I think the M flag says "you can get an address via DHCP" - it doesn't
say "and don't get an address via any other means".

From RFC 4861:

    M              1-bit "Managed address configuration" flag.  When
                   set, it indicates that addresses are available via
                   Dynamic Host Configuration Protocol [DHCPv6].

If you want to disable SLAAC, you instead use the AdvAutonomousFlag in
the Prefix Information option included for the given prefix in the
link's Prefix List.

DHCP has a couple of hundred defined options.  Vendors have tried
adding ONE to the RA protocol (DNS servers) as replacement
functionality.  That leaves them a few hundred options short, in
my book.

Which is what the O bit was for.

Welll - the number of options defined so far for DHCPv6 is very small
compared to the number of options defined for DHCPv4. I think that's
what Leo meant. The "O" bit will avail you naught if you want, for
example, a boot server address.

I do think though, that assuming DHCP is the way to get some of these
things might be shooting from the hip. Perhaps there is a better way,
with IPv6?

The difficulty is that now everyone is in a tearing hurry; they just
want everything to work the exact same way, and they want it NOW. There
is "suddenly" no time to work out better ways. And goodness knows there
must be a better way to boot a remote image than delivering an address
via DHCP!

With apologies to the musical "Keating":

   "Give us back our comfy little network
    Take us back to safer days of yore
    Nothing alien or scary, la-di-da or airy-fairy
    Just put it back the way it was before..."

Regards, K.

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Karl Auer (kauer () biplane com au)                   +61-2-64957160 (h)
http://www.biplane.com.au/kauer/                   +61-428-957160 (mob)

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