v6 subnet size for DSL & leased line customers

Mark Smith nanog at 85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org
Fri Dec 21 21:16:25 UTC 2007

On Fri, 21 Dec 2007 08:31:07 -0800
Owen DeLong <owen at delong.com> wrote:

> > The primary reasons I see for separate networks on v6 would include
> > firewall policy (DMZ, separate departmental networks, etc)...
> >
> This is certainly one reason for such things.
> > And I'm having some trouble envisioning a residential end user that
> > honestly has a need for 256 networks with sufficiently differently
> > policies.  Or that a firewall device can't reasonably deal with those
> > policies even on a single network, since you mainly need to protect
> > devices from external access.
> >
> Perhaps this is a lack of imagination.
> Imagine that your ethernet->bluetooth gateway wants to treat the  
> bluetooth
> and ethernet segments as separate routed segments.

I think this is also showing a bit of a lack of imagination:

> I think it makes sense to assign as follows:
> /64 for the average current home user.
> /56 for any home user that wants more than one subnet
> /48 for any home user that can show need.

Well, it doesn't really make sense to me - I think it's far more
conservative than it has to be. Even spending time on considering and
evaluating the checkboxes for the last two options is time that could
be better spent on something else, and probably costs more than the
IPv6 address space (and associated costs) saved by being conservative
with the allocations.

I'd be interested to know *why* that makes sense to you - the justifications.

I'd also be interested to know what you'd *want* if you were asked how
you'd like to structure IPv6 addressing, if you didn't have any history
of having to be conservative with IPv4 addressing. IOW, imagine IPv4
didn't exist, and therefore your thinking about IPv6 isn't influenced
by your history with IPv4.



        "Sheep are slow and tasty, and therefore must remain constantly
                                   - Bruce Schneier, "Beyond Fear"

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