using "reserved" IPv6 space

Karl Auer kauer at
Tue Jul 17 02:35:36 UTC 2012

On Mon, 2012-07-16 at 22:04 -0400, Lee wrote:
> Each site gets a /48.  Even the ones with less than 200 people.
> [...]
> Which is *boring*.  Nothing novel, no breaking out of "IPv4 think"
> aside from massively wasting address space.

It's only a waste if you get nothing for it. By using /64 everywhere you
get a more homogeneous network, easier to administer, manage, document,
maintain... There are similar advantages, writ larger, to using /48 for
every site.

Whether you have 2, 20, 200, 2000 or 20,000 hosts in a /64 subnet, you
have still only used 0% of it, to a dozen or more decimal places.
IPv4-think says that's a waste. IPv6-think says "great - all my subnets
are large enough". Resizing IPv4 subnets is common; resizing IPv6
subnets will be rare.

IPv4-think is conserving addresses. IPv6-think is conserving subnets. We
don't buy dining chairs based on the number of atoms in them - we buy
enough to seat the people who need seating.

Regards, K.

Karl Auer (kauer at

GPG fingerprint: AE1D 4868 6420 AD9A A698 5251 1699 7B78 4EEE 6017
Old fingerprint: DA41 51B1 1481 16E1 F7E2 B2E9 3007 14ED 5736 F687
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 230 bytes
Desc: This is a digitally signed message part
URL: <>

More information about the NANOG mailing list