On 13/01/13 20:05, Tony Langdon wrote:
> A /64 should do most home networks.

Where “most” doesn’t include power users. A /64 cannot be divided any
further without breaking router advertisement (which you REALLY do not
want to do). In fact, using anything other than a /64 on a direct
interface (i.e. not a route) is officially deprecated.

In addition, operating systems such as iOS or Android do not allow
static configuration of IPv6 and thus completely depend on router
advertisement.

A fair few non-power users use multiple subnets without realising it —
all the time I come across people who have purchased a wired-only ADSL
modem, and put a wireless router behind it. That’s two (currently IPv4,
could become IPv6 if CPE one day supports sub-DHCPv6-PD) subnets right
there.

(If you’ve ever wondered why most ADSL modem/routers default to
192.168.1.0/24, and most non-ADSL routers default to 192.168.2.0/24,
this is the precise use case in mind.)

I’m a power user, and have used 5 × /64’s out of my /56 at various
stages. So a /60 would do me nicely, but I can think of a couple of my
own clients who are approaching 16 separate subnets. A /56 would be
needed for them.

It’s easier to estimate IP allocation growth when you have to deal with
x number of customers, rather than needing to separately deal with
business/residential trends if you are delegating different sized
subnets to each demographic.

In other words, it’s much easier to just give a /56 to everyone. You’ve
gotta pick your battles. Squeezing 100% efficiency out of your IP
allocations isn’t one I want to fight.

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