Date: Fri, 14 Jun 2002 09:31:53 -0700 (PDT)
From: Michael Thomas <[EMAIL PROTECTED]>
Message-ID: <[EMAIL PROTECTED]>
| In the good old days, wasn't it rather common
| for clueless newbies to slavishly number their
| networks 192.6 or somesuch which was what they
| found in the network administrator manual examples?
Yes (that wasn't the number, it used to be imprinted on my
brain, but fortunately these days it is seen so rarely that
I have forgotten the value - I think it had a 200 in it though,
not that it matters - 192.9.200 ??).
It was this kind of thing that led to 1918 addresses - the IETF
invented (allocated) them precisely because of the problems that
this (and other number "borrowing") caused.
| They worked just great up until the time they
| wanted to connect to the real net, right?
yes.
| Assuming that you _never_ want to globally
| advertise that prefix -- which is what site
| locals are intended for -- does it actually
| make any difference which prefix you choose?
Yes. Because if you happen to choose a prefix that is someone
else's globally allocated prefix, you can never talk to them.
Or more likely, you find you have to renumber because you want
to talk to them (if you're lucky, and never do, there's no issue).
If you're ever going to be in the position of having to renumber
then the address you have isn't stable.
Of course, if "you" happen to be a large ISP, instead of an end-site,
then not only can "you" not communicate with the true assignee of the
address, but nor can anyone else who uses you for connectivity.
| Why does IETF have to sanction one?
One, as distinct from two or three or ... it doesn't. One as
distinct from zero, so you know the address that you're going to
be using will never be one that someone else uses (and you might
need to use to communicate with them - their using it as a private
address is harmless of course).
| Why not just let people make their own decisions?
They don't have enough information to make a good decision.
Allocate several prefixes (like was done in 1918) and allow
people to choose which they want to use if you like, that's
fine - but they need to be prefixes reserved for the purpose.
| BTW: isn't there already an implicit "site local"
| address space for v6 with net 10 v4 mapped
| address?
If you mean the ::/80 address space (::/96 and ::FFFF:/96) then
if there's any addresses that it would be nice to see vanish,
it would be those (and one hopes that they will do so once v4
has finally departed - sometime in the far future). In any case
these ones don't work, because you don't get a /48 prefix out
of them,
If you mean 2002:0A00::/24 (which aren't usually called v4 mapped
addresses I thought) then that's certainly a possibility,
but it is also just a bit pattern variation on fec0::/10, and
I thought we'd all agreed that bit patterns cannot possibly be
what's important here. I don't care what the bit pattern is,
just as long as it exists (but since fec0::/10 already exists,
I'd want to see a good justification to alter it). I would also
expect 2002::/16 to vanish, sometime in the far future, as well
of course, that one may even happen before the other as 2002
remains viable only while the IPv4 global routing system works,
::/80 (the two sub-groups of that of relevance) is still usable
while there's any IPv4 left anywhere.
kre
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