Addressing plan exercise for our IPv6 course

Joe Maimon jmaimon at
Thu Jul 22 23:09:09 CDT 2010

Owen DeLong wrote:
> On Jul 22, 2010, at 5:37 PM, Matthew Kaufman wrote:
>> Valdis.Kletnieks at wrote:
>>> If it doesn't make sense for IPv4, why would you want to do it for IPv6?
>> "Home wifi router" vendors will do whatever it takes to make this work, so of course in your scenario they simply implement NAT66 (whether or not IETF folks think it is a good idea) however they see fit and nobody calls.
>> Matthew Kaufman
> Well, wouldn't it be better if the provider simply issued enough space to
> make NAT66 unnecessary?
> Owen

If the only reason the common denominator of internet service has not 
and does not come with more than minimum sufficient supply of IPv4 is 
due to scarcity, then it may be reasonable to hope that in the future 
the common denominator of internet service will include near limitless 
IPv6 addresses for its end users. Very likely, that is better.

However, even then, there is no guarantee that the common denominator 
CPE for this service wont have NAT66 features, maybe even turned on by 

And if those CPE do have the feature on by default, then there is no 
reason for vendors to do more than supply the single /128 or even /64.

Perhaps CPE will respond to a market condition of that nature by 
throwing out /64 subnetting rules and implementing their own 
divide-and-consume addressing scheme. And so it may go on and on. Action 
by action, reaction by reaction, the common scenario evolves, constantly.

Automatic extension of dynamic routing protocols deep into the customers 
network may not be as sound a notion and as universally adoptable as is 
currently viewed.

I believe it is way too early to predict with any confidence how this 
will play out. NAT44 did not become the method-du-jour until well after 
the scarcity was felt by the actual end users of the IPv4 network. Its 
increasing effect on network design and engineering came later yet.

So any addressing plan that does not leave a hefty chunk of space 
reserved to be available for unknown future uses, a la IANA's other /3s, 
strikes me as unable or unwilling to withstand the test of time, by design.

It would be an epic tragedy if down the road those other /3's were 
deemed as unusable as 240/4, maybe even for similar reasons.

I suspect the perfect address plan is the holy grail of networking and 
just as locatable.


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