[128070] in North American Network Operators' Group
Re: Addressing plan exercise for our IPv6 course
daemon@ATHENA.MIT.EDU (Fred Baker)
Sat Jul 24 02:34:42 2010
From: Fred Baker <fred@cisco.com>
In-Reply-To: <20100724152046.6df037f7@opy.nosense.org>
Date: Sat, 24 Jul 2010 08:34:13 +0200
To: Mark Smith <nanog@85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
I tend to think a /60 is a reasonable allocation for a residential user. =
In my home I have two subnets and will in time likely add two more:=20
- general network access
- my office (required to be separate by Cisco Information Security =
policy)
- (future) would likely want routable separate bandwidth for A/V at =
some point
- (future) Smart Grid HAN will likely be its own subnet
If my wife went to work for a company with an infosec policy like =
Cisco's, that becomes a fifth subnet. Yes, 16 to choose from seems =
reasonable.
/56 seems appropriate to a small company, /48 for a larger company, and =
I could see a market for a /52. A company that needs more than a /48 is =
likely to also be using ULAs for some of its areas, which is an =
automatic extension, and could always justify another /48 (or one per =
continent) if it really needed them.
Could I do all this within a /64? Of course, with some thought, and by =
getting the Smart Grid and office prefixes from other sources (Cisco, my =
utility) and running them over a VPN (which I do anyway). The question =
is why I should have to.=20
Why four bit boundaries? Because we're using hexadecimal, and each =
character identifies four bits. It makes tracking numbers simple - no =
"remember to count by N" as in IPv4. It's not magic, but to my small =
mind - and especially for of non-technical residential customers - it =
seems reasonable.
And yes, I think the logic behind a 48 bit MAC address is reasonable =
too.
On Jul 24, 2010, at 7:50 AM, Mark Smith wrote:
> On Fri, 23 Jul 2010 13:26:43 -0700
> Matthew Kaufman <matthew@matthew.at> wrote:
>=20
>> sthaug@nethelp.no wrote:
>>>> It is not about how many devices, it is about how many subnets, =
because you
>>>> may want to keep them isolated, for many reasons.
>>>>=20
>>>> It is not just about devices consuming lots of bandwidth, it is =
also about
>>>> many small sensors, actuators and so.
>>>>=20
>>>=20
>>> I have no problems with giving the customer several subnets. /56 is
>>> just fine for that.
>> /56? How about /62? That certainly covers "several"... and if you're=20=
>> really worried they might have too many subnets for that to work, how=20=
>> about /60?
>>> I haven't seen any kind of realistic scenarios
>>> which require /48 for residential users *and* will actually use lots
>>> and lots of subnets - without requiring a similar amount of manual
>>> configuration on the part of the customer.
>>>=20
>>> So we end up with /56 for residential users.
>>>=20
>> Only because people think that the boundaries need to happen at=20
>> easy-to-type points given the textual representation. /56 is still=20
>> overkill for a house. And there's several billion houses in the world =
to=20
>> hook up.
>>=20
>=20
> So you're also strongly against 48 bit Ethernet MAC addresses? =
Dropping
> the two bits for group and local addresses, that's 70 368 744 177 664
> nodes per LAN. How ridiculous! What were those idiots+ thinking!
>=20
> "48-bit Absolute Internet and Ethernet Host Numbers", by Yogan K. =
Dalal,
> Robert S. Printis, *July 1981*
>=20
> http://ethernethistory.typepad.com/papers/HostNumbers.pdf
>=20
>=20
>=20
>=20
> + not actually idiots
>=20
>=20
http://www.ipinc.net/IPv4.GIF
