Re: Additional Documentation Prefixes (was Re: AD Evaluation : draft-ietf-6man-ra-pref64-06)

Michael Richardson <> Sun, 03 November 2019 17:18 UTC

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From: Michael Richardson <>
To: Suresh Krishnan <>
cc: Lorenzo Colitti <>, IETF IPv6 Mailing List <>
Subject: Re: Additional Documentation Prefixes (was Re: AD Evaluation : draft-ietf-6man-ra-pref64-06)
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Date: Sun, 03 Nov 2019 12:18:27 -0500
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Suresh Krishnan <> wrote:
    >> I agree with you.
    >>> Is there a larger documentation prefix than
    >> I wish that there was.

    > Me too. I also think a larger prefix could be useful. Similarly a block
    > that would differentiate it as an example of private space to be used.

    >> Maybe we could carve out of class E space as a /20 of documentation space.

    > Sounds like a plan. If you write something up, I would be willing to AD
    > sponsor something like this. The biggest issue with repurposing E space
    > was that it would hit a lot of bogon filters. In this case that is a
    > desirable feature.

Okay, I will write something if there is further support.
Should it update or replace RFC5737?

    >> I'd also like to have three or four additional IPv6 documentation prefixes,
    >> plus some documentation space from ULA-R and ULA-C.

    > What is ULA-R? Did you mean ULA-L? If so, it would be a pain to reserve
    > something now since we also need to update RFC4193 to make sure that
    > the Random “Global ID”s will not collide with the reserved prefixes. If
    > ULA-C does take off, this would be a good idea to do something like
    > this.

I guess L=1 is why you call it ULA-L. I have known it as ULA-Random.
We are both talking about RFC4193 though.  So such a document would need to
update RFC4193.

    >> I'd like the IPv6 documentation prefixes to have a pretty high Hamming
    >> Distance from each other to maximize the visual distinction.

    > We have a /32 for this. Plenty of ways to be visually distinct
    > including some of the common ones I have used :-)

    > 2001:db8:abba::/48
    > 2001:db8:beef::/48
    > 2001:db8:cafe::/48
    > 2001:db8:dead::/48
    > 2001:db8:face::/48
    > 2001:db8:c001::/48

I'm not sure that I agree.
I don't see why we need to be so stingy about Documentation Prefixes in IPv6.
Using part of 3ffe::/16 would appeal to me.

Michael Richardson <>ca>, Sandelman Software Works
 -= IPv6 IoT consulting =-