IPv6 end user addressing

Doug Barton dougb at dougbarton.us
Fri Aug 5 14:18:28 CDT 2011

On 08/05/2011 09:17, Brian Mengel wrote:
> In reviewing IPv6 end user allocation policies, I can find little
> agreement on what prefix length is appropriate for residential end
> users.  /64 and /56 seem to be the favorite candidates, with /56 being
> slightly preferred.
> I am most curious as to why a /60 prefix is not considered when trying
> to address this problem.  It provides 16 /64 subnetworks, which seems
> like an adequate amount for an end user.
> Does anyone have opinions on the BCP for end user addressing in IPv6?

You've had a lot of good opinions already, but here's one more vote for
/56 being the absolute minimum.

That said, the strategy I've suggested in the past is to reserve for
each customer the largest block that your RIR will recognize as
reasonable (note, that's reasonable, not theoretically justifiable) for
end user assignment. Then if down the road it turns out that you need
more space and for some unimaginable reason you can't get more from the
RIR you can go back and start bifurcating the blocks you've reserved.

For example, if you reserve a /48 per customer but actually use the
first /56 out of it, you are safe if _you_ need the other /56 for some
reason, or if the customer needs to expand into the full /48.




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