nanog mailing list archives

Re: Private use of non-RFC1918 IP space (IPv6-MW)


From: Seth Mattinen <sethm () rollernet us>
Date: Wed, 04 Feb 2009 16:08:13 -0800

Patrick W. Gilmore wrote:
On Feb 4, 2009, at 6:56 PM, Scott Howard wrote:
On Mon, Feb 2, 2009 at 9:35 PM, Patrick W. Gilmore
<patrick () ianai net>wrote:

Except the RIRs won't give you another /48 when you have only used one
trillion IP addresses.

Of course they will!  A /48 is only the equivalent of 65536 "networks"
(each
network being a /64).  Presuming that ISPs allocate /64 networks to each
connected subscriber, then a /48 is only 65k subscribers, or say around a
maximum of 200k IP addresses in use at any one time (presuming no NAT
and an
average of 3-4 IP-based devices per subscriber)

IPv4-style utilization ratios do make some sense under IPv6, but not
at the
address level - only at the network level.

First, it was (mostly) a joke.

Second, where did you get 4 users per /64?  Are you planning to hand
each cable modem a /64?



That was the generally accepted subnet practice last time I had a
discussion about it on the ipv6-ops list. I'm not an ISP, but I have a
/48 and each subnet is a /64. Some devices will refuse to work if you
subnet smaller than a /64. (Yes, poorly designed, etc.)

~Seth


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