Re: [vserver] assigning less than /64 to individual guests

FYI

----- Forwarded message from Michael Richardson <mcr@sandelman.ca> -----

From: Michael Richardson <mcr@sandelman.ca>
Date: Tue, 17 May 2011 13:10:40 -0400
To: Eugen Leitl <eugen@leitl.org>
cc: debian-ipv6@lists.debian.org
Subject: Re: [vserver] assigning less than /64 to individual guests
X-Mailer: MH-E 8.1; nmh 1.1; XEmacs 21.4 (patch 22)

>>>>> "Eugen" == Eugen Leitl <eugen@leitl.org> writes:
    Eugen> Just sent that to the vserver list, but figured this is at
    Eugen> least as relevant.

    Eugen> So am I in the clear to parcel out a /64 in /80s, as long as
    Eugen> all the /80 are all on the same LAN or VLAN? No autoconfig
    Eugen> breakage ensues? Is 48 bits really enough for anybody?

If you are saying that you will allocate /80s to each vserver, but
actually they will not be layer-2 isolated from each other, this is just
an administrative partition, then I think it's a good idea.

You can't use autoconfig for the parts that are in the /80s.
You can arrange for your /80s to never overlap the autoconfigured stuff.
OUI-64s, when generated from OUI-48s (i.e. mac addresses) always have
ff:fe as the middle 16 bits.

In addition, bit 6 in the OUI-64 (which is bit 1 in little bit-endian,
the bit after the "broadcast" bit) will be set if the OUI-64 is believed
to be globally unique. Note that if you have IPv6 Privacy Extensions
on, then autoconfig will not necessarily set bit 6.
I would have to lookup to determine in fact privacy extensions will set
the middle 16 bits in any predictable fashion.

Permitting autoconfig to work seems like a nice thing to retain.

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