ipv6 addressing - non-routable equivalents?

[Jonathan Guthrie]

On Sat, 30 Sep 2000, Antonio Querubin wrote:

> On Sat, 30 Sep 2000, Bill Manning wrote:
 
> > 	  If you have:  201:0600:0004:80cf::/48 and (remember) the
> > 	  bits from 65-128 are "reserved" for your MAC or e164 address,
> > 	  then you have /49 to /64 to carve up as subnets.
> > 	  16 delegation points, e.g. the functional equivalant of an
> > 	  IPv4 /16.  Does that help?
 
> Is it really required that we use the MAC address in bits 64-128?  Ie.
> what prevents someone from just starting with some arbitrary number in the
> subnet field?  Or for that matter what really prevents subnetting beyond a
> /64?

You need to read the rfc that talks about constructing an IPv6 address
from an Ethernet address.  Basically, what I understand is that as long as
the global bit is not set, you can generate any address you want for
bits 64-127.  You use such addresses for things like tunnel endpoints,
which aren't associated with Ethernet adapters and so the technique for
converting Ethernet adapters to IPv6 addresses doesn't apply.

It is also my understanding that tunnels (and, presumably, point-to-point
IPv6 links like PPP or HDLC WAN sessions although I've never seen it done
because I'm still new to this IPv6 thing) are usually set up as /127's.
I do it this way for my downstream tunnels and it works.  Those addresses
are primarily of local interest, so you reset the global bit for them and
pick them in pairs.  It works because nobody expects bits 64-127 to be
unique if the global bit is reset.

What I don't understand is what to do if you want multiple global
addresses on a single computer.  Is there some way of generating multiple
IPv6 addresses from a single Ethernet address or am I supposed to generate
random global addresses and do a collision detection or do I have to buy a
bunch of old, dead Ethernet cards and use their addresses?  With the large
address space available in IPv6, it makes sense to use address-based
virtual hosting and server addresses should be global, or so I understand.
-- 
Jonathan Guthrie (jguthrie@brokersys.com)
Brokersys  +281-580-3358   http://www.brokersys.com/
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