Subject: IPv6 addresses with embedded private IPv4 addresses

From: "Dave Thaler" <[email-masked]>
Date: Thu, 15 Feb 2001 14:32:07 -0800

I'd like to ask for some general consensus on the following questions:

1) Are "::10.1.1.1" and "::169.254.1.1" legal IPv6 addresses?
   (They look like global IPv6 addresses, but aren't globally unique.)
   RFC 2373 does not mention any such restriction, and so
   implies "yes".

2) Similarly, is "2002:0A01:0101:..." a legal IPv6 address?
   The current 6to4 draft implies "no".
   
3) Is it reasonable that the answers to the above two questions
   could be different?

(I'd personally rather the answer be the same for both, that
answer probably being "no", as this avoids a lot of ugly problems.)

And before anyone responds saying that "::10.1.1.1" should be
allowed so that you can talk between two hosts in a private IPv4
network, keep in mind that draft-templin-ngtrans-v6v4compat-*.txt
allows you to do the same thing with "fe80::200:5efe:10.1.1.1", which
is clearly a link-local address (on an encapsulation link covering the
private area) and so avoids the ugly problems "::10.1.1.1" has.

-Dave
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From: Francis Dupont <[email-masked]>
Date: Fri, 16 Feb 2001 09:23:16 +0100

In your previous mail you wrote:

   
=> no

=> no

=> no

The argument is: even if these addresses seem legal in an internet
*NOT* connected to the Internet, IPv6 provides local scoped and
not ambiguous addresses which have none of RFC 1918 problems.

Regards

[email-masked]

PS: what is your purpose? Add this in BCP filters?

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From: Brian E Carpenter <[email-masked]>
Date: Fri, 16 Feb 2001 08:04:55 -0600

6to4 is meant to do more than imply it:

>    The V4ADDR MUST be
>    a duly allocated global IPv4 address, which MUST be unique within the
>    private network.  The Intranet thereby obtains globally unique IPv6
>    addresses even if it is internally using private IPv4 addresses [RFC
>    1918].

And BTW it isn't a draft; it's an RFC. I don't know if the announcement is
out, because I don't seem to be able to receive email this morning, only
send it, but the authors' 48 hour check on the RFC just finished.

Personally I think the answer should be to insist on global addresses
in IPv4-compatible addresses too. The scenarios using NAT addresses here
are too horrible to contemplate.

  Brian

-- 
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Brian E Carpenter 
Program Director, Internet Standards & Technology, IBM 
On assignment for IBM at http://www.iCAIR.org 
Board Chairman, Internet Society http://www.isoc.org
Non-IBM email: [email-masked]
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From: Brian E Carpenter <[email-masked]>
Date: Fri, 16 Feb 2001 08:04:55 -0600

Brian