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Re: IPv6 end user addressing
From: Owen DeLong <owen () delong com>
Date: Mon, 8 Aug 2011 13:56:00 -0700


On Aug 8, 2011, at 5:43 AM, Valdis.Kletnieks () vt edu wrote:

On Mon, 08 Aug 2011 10:15:17 +0200, Mohacsi Janos said:

- Home users - they usually don't know what is subnet. Setting up 
different subnets in their SOHO router can be difficult. Usually the 
simple 1 subnet for every device is enough for them. Separating some 
devices into  a separate subnets is usually enough for the most 
sophisticated home users. If  not then he can opt for business service....

You don't want to make the assumption that just because Joe Sixpack doesn't
know what a subnet is, that Joe Sixpack's CPE doesn't know either.

And remember that if it's 3 hops from one end of Joe Sixpack's internal net to
the other, you're gonna burn a few bits to support heirarchical routing so you
don't need a routing protocol. So if Joe's exterior-facing CPU gets handed a
/56 by the provider, and it hands each device it sees a /60 in case it's a
device that routes too, it can only support 14 devices.  And if one of the
things that got handed a /60 is a wireless access point or something, it's only
going to be able to support 15 or so subnets. So a simple topology of only a
half dozen devices can burn up 8 bits of subnet addressing real fast. Yes, you
can conserve bits by being more clever, but then you probably need an IGP of
some sort....



YOu lost a /60 somewhere in thereā€¦

I understand 1 /60 for the primary device.
You accounted for 14 /60s to other subordinate devices.
Presumably the /64(s) that connect the other subordinate devices to the
primary router are from within that first /60, so, where did the 16th /60 go?

Finally, for things that are building automatic hierarchical topologies, it
seems only sane to me that they would implement some form of OSPF
to facilitate the routing. There's no reason that can't be equally automated.

Owen

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