IPv6 Addressing Help

TJ trejrco at gmail.com
Fri Aug 14 12:06:06 CDT 2009

>-----Original Message-----
>From: Roland Dobbins [mailto:rdobbins at arbor.net]
>On Aug 14, 2009, at 10:31 PM, Chris Gotstein wrote:
>> I'm just not able to wrap my brain around the subnetting that needs to
>> be done on the router.
>One of the things which has struck me as being fairly insane about current
>recommended 'best practices' for IPv6 addressing is the practice of wasting
>huge blocks of addresses on p2p links; even given the gigantic address
>in a world in which every soda-can, every window-blind, and swarms of
>nanobots injected into one's bloodstream will potentially become spimes,
>just seems grossly short-sighted.

It is all a matter of perspective.
If you want to use /126s (or whatever longer-than-64bit-prefix-you-like)
that is ~OK - it certainly works! - but you may be complicating your life in
the future.
It is "your network" - build it however you wish, just be sure of the
benefits and drawbacks associated with those choices.

(Purely an off-the-top-of-my-head hypothetical: What if PtP links become
drastically less common, and you need to re-address your network from ~/126s
to /64s because of that?  You are causing yourself pain, and for what gain?
To conserve a resource that is not (and according to some, will effectively
never be) in short supply?)   

A great counter-point to this is that if you do use /64s (or for that matter
- anything shorter than the currently-not-recommended /127s, AFAIK), you
should apply ACLs to them to prevent ping-pong.

((FWIW - counting the number of individual address being used is a
non-starter ... ~18,000,000,000,000,000,000 addresses on each segment is
more than enough for any solution I expect in the relevant future.  I am not
saying the goal of conservation is bad (e.g. - I like /56s to homes instead
of /48s), just trying to keep things in perspective.))

Pick your flavor of answer, and drink heavily.  I prefer coffee ... or

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