Using /126 for IPv6 router links

Nathan Ward nanog at
Wed Jan 27 21:29:03 UTC 2010

On 28/01/2010, at 1:51 AM, Randy Bush wrote:

>>>> the general intent of a class B allocation is that it is large enough
>>>> for nearly everybody, with nearly everybody including all but the
>>>> largest of organisations.
>>> That would, indeed, work if we weren't short of class B networks
>>> to assign.
>> Would you clarify? Seriously?
> we used to think we were not short of class B networks

We also used to have a protocol with less total addresses than the population of the planet, let alone subnets.

In 2000::/3, assuming we can use 1 in every 4 /48s because, well, I'm being nice to your point, we still have 1300 /48s per person.

And that's /48s.
What if say 50% of the address space is /48s and 50% of the address space is /56s?
Then we have 675,000 networks per person.

If we botch that up then we've done amazingly badly.
Then we'll move on to 4000::/3.

Nathan Ward

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