using "reserved" IPv6 space

Owen DeLong owen at
Sun Jul 15 19:22:14 UTC 2012

On Jul 15, 2012, at 8:58 AM, Grzegorz Janoszka wrote:

> On 2012-07-15 15:30, Scott Morris wrote:
>>> There was also in the past fec0::/10. For BGP updates you should be safe
>>> to filter out FC00::/6.
>> Unless I've missed something, RFC4193 lays out FC00::/7, not the /6.  So
>> while FE00::/7 may yet be unallocated, I don't think I'd set filters in
>> that fashion.
>> Reasonably, wouldn't it be more likely to permit BGP advertisements
>> within the 2000::/3 range as that's the "active" space currently?
> FF00::/8 are multicast, FE80::/10 are reserved for link-local. In the
> past you had FEC0::/10 as a kind of private addresses.
> Allowing 2000::/3 is fine as well. Btw - what are the estimates - how
> long are we going to be within 2000::/3?

Quite probably longer than anyone now reading this message will be alive.

So far, I believe IANA has allocated 6 or 7 of the /12s from 2000::/3 to RIRs.

That leaves at least 500+ /12s still to go.

Even with ARIN's extremely liberal policies, I expect ARIN will be able to number all of their service region in its current state from 3 or 4 /12s. Assuming this somewhat follows world population, APNIC should require <=12 /12s, RIPE should need <= 6 /12s, AfriNIC should require <= 6 /12s, and LACNIC should require <= 4 /12s.

Adding that up, I get 4+12+6+6+4 = 32 /12s if the entire world were to adopt ARIN's extremely liberal (which I think is a good thing) IPv6 allocation policies.

Assuming that the world population (and thus address need) continues on a 1.5% per year growth trajectory, that would double the population every 46+ years. With a lifespan of ~100 years and assuming that everyone reading this is now over the age of 10, that's 4*32 = 128 /12s in the next 92 years, leaving us with 384 /12s still sitting on the shelf after the last of us now reading this message is dead.

So, even if I'm wrong and it's 3 times what I anticipate, we still won't use up 2000::/3 in any of our lifetimes.


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