Re: what problem is solved by proscribing non-64 bit prefixes?

[Brian E Carpenter <brian.e.carpenter at gmail.com>]

On 2008-10-01 08:26, Brian Dickson wrote:
...
> we would ideally also have corresponding IPv6 subnets that are
> algorithmically derived from the IPv4 subnets.

I used to think that was a good way to design an initial
IPv6 addressing plan. But from helping people design a real
addressing plan for a real campus with many years of IPv4
history, I've reached the conclusion that it's a really bad idea.
It's much better to design a clean IPv6 plan from the ground up,
rather than sweeping up the messy history of the IPv4 plan.

If you design a clean IPv6 plan that way, there doesn't seem to be
any incentive whatever to use anything other than /64 as
subnet prefixes (except for the router-router links, as Pekka
mentioned). There's a strong incentive in favour of /64,
i.e. the ability to use SLAAC, privacy addresses, and CGAs.

    Brian C

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