Re: On consistency and 192.0.0.0/24

["Jakob Heitz \(jheitz\) via NANOG" <nanog () nanog org>]

RFC 5736 was obsoleted by RFC 6890.
It says in part:

2.2.1.  Information Requirements

   The IPv4 and IPv6 Special-Purpose Address Registries maintain the
   following information regarding each entry:
…
   o  Forwardable - A boolean value indicating whether a router may
      forward an IP datagram whose destination address is drawn from the
      allocated special-purpose address block between external
      interfaces.
…

That means that some IP addresses in the block 192.0.0.0/24 may be routable.
So, I would not make this a bogon.

A better way to filter IP routes is by policy, for example based upon
IRR and RPKI records.

Kind Regards,
Jakob

---------- Original message ----------
Date: Tue, 14 May 2024 12:00:15 +0200 (CEST)
From: borg () uu3 net


[10] 192.0.0.0/24 reserved for IANA IPv4 Special Purpose Address Registry
[RFC5736]. Complete registration details for 192.0.0.0/24 are found in
[IANA registry iana-ipv4-special-registry].

Was RFC5736 obsoleted? I think not, so I would treat it as bogon.

Its a nice tiny subnet for special purposes. I personaly use it
as my Internal VM Net on my desktop for example.


---------- Original message ----------

From: John Kristoff <jtk () dataplane org>
To: NANOG <nanog () nanog org>
Subject: On consistency and 192.0.0.0/24
Date: Mon, 13 May 2024 16:18:47 -0500

As one to never let a good academic question go unasked... what is it
about 192.0.0.0/24 that is or isn't a bogon. This doesn't seem so
straightforward an answer to me, at least in theory.  Although in
practice it may already be decided whether one likes the answer or not.

192.0.0.0/24 was originally assigned to IANA for "protocol assignments"
in IETF RFC 5736, and later added to the list of reserved / special use
addresses in IETF RFC 6890 (aka BCP 153).   There is a corresponding
IPv6 block (2001::/23), but it has a significantly different history.

Team Cymru's bogon list includes the v4 prefix.  NLNOG's bogon
filtering guide does not.  When I asked Job about NLNOG's position he
said:

  "I was unsure what this prefix??s future plans would be and erred on
  the side of caution and didn??t include this prefix in the NLNOG bogon
  list recommendations."

The /24 as specified is not for "global" use, but some of the more
specific assignments are or can be.  See:
<https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml>.

> From my cursory examination I can't find cases where the v4 prefix or
more specifics have been publicly announced to any significant degree.
This however is not the case for the IPv6 prefix (e.g., the AS112
project, Teredo).

Maybe you'd say the /24 should be filtered, but not the more specifics
that are deemed available for global use.  That might be reasonable,
except many reasonable people will filter small prefixes.

IANA's language may have put any "do not filter" camp in a relatively
weak position:

  "Address prefixes listed in the Special-Purpose Address Registry are
  not guaranteed routability in any particular local or global context."

I can't remember hearing anyone complaining about bogon-related
reachability problems with the aggregate IANA prefixes generally.  Is
there a strong case to make that ops should not bogon filter any
addresses in these prefixes?  At least with IPv4?  What about for IPv6?

John