[121725] in North American Network Operators' Group
Re: Using /126 for IPv6 router links
daemon@ATHENA.MIT.EDU (Owen DeLong)
Mon Jan 25 20:06:45 2010
From: Owen DeLong <owen@delong.com>
In-Reply-To: <9e246b4d1001251102u2b6ca6b1le4b7f259ea2d505b@mail.gmail.com>
Date: Mon, 25 Jan 2010 17:01:29 -0800
To: Tim Durack <tdurack@gmail.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
>=20
> 2^128 is a "very big number." However, from a network engineering
> perspective, IPv6 is really only 64bits of network address space. 2^64
> is still a "very big number."
>=20
> An end-user assignment /48 is really only 2^16 networks. That's not
> very big once you start planning a human-friendly repeatable number
> plan.
>=20
An end-user MINIMUM assignment (assignment for a single "site") is
a /48. (with the possible exception of /56s for residential customers
that don't ask for a /48).
I have worked in lots of different enterprises and have yet to see one =
that
had more than 65,536 networks in a single site. I'm not saying they =
don't
exist, but, I will say that they are extremely rare. Multiple sites are =
a different
issue. There are still enough /48s to issue one per site.
> An ISP allocation is /32, which is only 2^16 /48s. Again, not that =
big.
>=20
That's just the starting minimum. Many ISPs have already gotten much =
larger
IPv6 allocations.
> Once you start planning a practical address plan, IPv6 isn't as big as
> everybody keeps saying...
It's more than big enough for any deployment I've seen so far with =
plenty
of room to spare.
Owen
