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

[Mohacsi Janos <mohacsi at niif.hu>]

On Wed, 1 Oct 2008, Alexandru Petrescu wrote:

> michael.dillon at bt.com wrote:
> > > In a typical IPv6 ADSL household landscape...
> > >
> > > An ADSL IPv6 operational deployment offers a /64 prefix at home.
> > > With that, I can't subnet _and_ use IPv6 stateless auto-configuration.
> >
> > In a typical IPv6 ADSL household landscape the ISP will assign you a
> > /48 with plenty of subnetting space.
>
> Not sure, FWIW, in the IPv6 ADSL household I live in gives me a /64 and not 
> /48 (see draft-despres-v6ops-6rd-ipv6-rapid-deployment-01.txt).
>
> That's typical for me but I don't know about the other deployed IPv6 ADSL, do 
> they give /64 or shorter prefixes?


The draft-despres-v6ops-6rd-ipv6-rapid-deployment-01.txt is largely 
irrelevant in this discussion, This draft describing a particular solution 
that can be implemented by the ISPs if:
1. they have complete operational control over the CPEs installed users
2. They want to implement IPv6 quickly
3. They users are using only one subnets which is the allocated /64.


In general - my recommendation when I giving tutorials about IPv6:

- /48 to /128 is delegated to end users
- /48 general case, /47 if justified for bigger networks
- /64 if one and only one network is required
- /128 if it is sure that one and only one device is going to be connected

between /48 - /64 up to you if you are cautious about address conservation:
- but use nibble boundary for easier reverse DNS delegation.

Regards,
		Janos Mohacsi:


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