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Using IPv6 with prefixes shorter than a /64 on a LAN

In message <4D4CA1B1.5060002 at brightok.net>, Jack Bates writes:
> On 2/4/2011 6:45 PM, Mark Andrews wrote:
> >
> > I used to work for CSIRO.  Their /16's which were got back in the
> > late 80's will now be /48's.
> That's why I didn't try doing any adjustments of X is the new /32. The 
> whole paradigm changes.

So why the ~!#! are you insisting on comparing IPv4 allocations with IPv6

>  Many ISPs devote large amounts of space to 
> single corporate network sites. Those sites will now have a single /48. 
> On the other hand, we currently give /32 to residential customers. They 
> also are getting a /48.
> Which is why the only way to consider address usage from an ISP and RIR 
> perspective is by how it is handed to a standard ISP of a given size. 

There are two sizes.  Those that fit into a /32 and those that don't.
The latter ones have to justify their allocations.

> Originally, ARIN was being overly restrictive and it was "/32 for every 
> ISP". They have loosened up, and will continue to do so (including ISP 
> to ISP) as future proposals come to fruition. So from an ISP 
> perspective, you have to consider your total IPv6 allocation size 
> (within the first 32 bits of IPv6) in comparison to your total IPv4 
> allocations summed.

No.  You need to compare it to the number of customer sites.  If you
have 1 customer with wires going to two locations thats two /48's.
> From what I can tell, on average, all ISPs are shifting between 8 and 
> 16 bits to the right from their total IPv4 size depending on their 
> primary customer type (residential ISPs shift less than ISPs that 
> primarily only service corporations).

Residential ISPs shift 16 bits (48-32=16).  You shift less if you
have less than 64000 customers sites and don't get address space
from a larger ISP.  Commercial ISPs shift more as what was multiple
address at one sites becomes 1 /48.

Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117,
Australia PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org