Re: More CPE

[Mark Smith <ipng@69706e6720323030352d30312d31340a.nosense.org>]

On Fri, 11 Jan 2008 09:34:24 +1300
Brian E Carpenter <brian.e.carpenter@gmail.com> wrote:

> On 2008-01-10 23:52, Mark Smith wrote:
> > On Thu, 10 Jan 2008 10:54:22 +0100
> > "Miguel A. Diaz" <miguelangel.diaz@consulintel.es> wrote:
> > 
> >> If both RA and DHPCPv6 are setup in the WAN port, the ISP has to
> >> manage two prefix pools: one for the point-to-point link (RA) and the
> >> other one for the delegated prefix (usually /48).
> >>
> >> That can be avoided by getting one /64 for the point-to-point link
> >> (RA) from the delegated prefix (/48) as explained at
> >> http://www.consulintel.euro6ix.org/ietf/draft-palet-v6ops-point2point-
> >> 01.txt
> >>
> >> This approach has benefits from both operational and routing
> >> aggregation perspectives and it may be taken into account by both ISPs
> >> and CPEs manufacturers.
> > 
> > I'm personally not against this addressing method, however I'm not all
> > that sure that might be a good idea for the customers. "Stealing" a /64
> > out of the customer's /48 creates opportunities for the customer to
> > accidently use it on their side of the CPE, breaking their external
> > connectivity. This probably would only happen occasionally (although as
> > an ISP you'd probably want to avoid the first 5, 20 or 100 /64s),
> > however when you have 10 000s or 100 000s customers, those occasions
> > can start to occur quite often, and those are calls your helpdesk has
> > to receive and deal with.
> > 
> > IOW, I think it's easier for all customers to remember, "this /48 is
> > mine", verses "this /48 is mine, except that one which my ISP assigns,
> > that I'll always have to remember to avoid."
> 
> Surely it should be the CPE itself that does the remembering? I don't
> envisage that SOHO users will be assigning IPv6 prefixes manually.
> And even if they did, a simple instruction like "start numbering your
> subnets at 1, because subnet 0 is used internally" should work.
> 

Possibly. OTOH, it could be the CPE vendors that pre-configure subnet
numbers to the one or more downstream interfaces for use with DHCP-PD,
and they might be in the habit of using the first 3 subnets, possibly
including zero.

If we were to recommend a /64 to "steal", I'd be suggesting 0xffff or
maybe 0x00ff (for /56 case) (although people like me tend to use those
specifically *because* they don't conflict with what other people
commonly choose :-) ).

Regards,
Mark.