Re: IPv6 address assignment for strictly point-to-point links and Device Loopbacks

TJ <trejrco@gmail.com> Fri, 21 September 2012 14:30 UTC

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From: TJ <trejrco@gmail.com>
Date: Fri, 21 Sep 2012 10:29:44 -0400
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Subject: Re: IPv6 address assignment for strictly point-to-point links and Device Loopbacks
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On Fri, Sep 21, 2012 at 10:16 AM, Usman Latif <osmankh@yahoo.com> wrote:

> Thanks for the feedback.
> I just want to confirm something.
>
> You wrote:
> "If you choose to do this, it is further recommended that you reserve the
> entire /64 so that - if needed in the future - you can expand this
> configuration _without_ a major renumbering event."
>
> This is the essence of what I want the IETF to put in one of its address
> recommendation RFCs because I have yet to see an RFC that says when you
> assign a /127 to a p2p link, you should/must reserve the whole parent /64
> for that p2p link also.
>
> Without this stated clearly there is likely to be some instances where
> readers interpret it the wrong way and end up assigning multiple p2p links
> with /127 subnets from a single given /64 and end up having to re-address
> their network in future when/if future standards use lower order 64 bits
> for special purposes.
>

Right, each PtP link should have it's own /64 assigned.
It should also be so-configured, but if you choose to alter that something
else (e.g. - a /127) may be configured.
But with that specific /64 still reserved per PtP link!



> Also you didn't talk about loopbacks at all.
>
> IMO any single loopback although a /128 should also have the whole parent
> /64 assigned to it because the issues with not doing that are pretty much
> the same as for p2p links
>

Correct, in fact - I intentionally excluded them :).
I would say a single /64 per site (or whatever demarcation / term you
choose to use) should be reserved for the purpose of assigning /128s to
loopbacks.  Not a /64 per loopback, a /64 per ~site to cover all of the
loopbacks within that ~site.
*I presume 18BB loopback addresses per ~site is sufficient? ;)*


/TJ