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Re: subnet prefix length > 64 breaks IPv6?
From: Ray Soucy <rps () maine edu>
Date: Wed, 28 Dec 2011 07:13:30 -0500

On Wed, Dec 28, 2011 at 6:23 AM, Iljitsch van Beijnum
<iljitsch () muada com> wrote:
Also somehow the rule that all normal address space must use 64-bit interface
identifiers found its way into the specs for no reason that I have ever been able
to uncover. On the other hand there's also the rule that IPv6 is classless and
therefore routing on any prefix length must be supported, although for some
implementations forwarding based on > /64 is > somewhat less efficient.

This ambiguity has always bothered me.  The address architecture RFC
requires a 64-bit interface identifier, but it's required to be
unenforced by implementation, which makes it more of a suggestion at
best.  I think the wording should be updated to changed MUST to
SHOULD.  That said, and despite my own use of prefix lengths other
than 64-bit, I do believe that a 64-bit prefix for each host network
is in our long-term interest.  Not having to size networks based on
the number of hosts is a good thing.  Features made possible by a
64-bit address space is a good thing.

Ray Soucy

Epic Communications Specialist

Phone: +1 (207) 561-3526

Networkmaine, a Unit of the University of Maine System

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