Re: Proposal to further clarify prefix length issues in I-D.ietf-6man-rfc4291bis

james woodyatt <> Thu, 09 March 2017 19:31 UTC

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From: james woodyatt <>
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Subject: Re: Proposal to further clarify prefix length issues in I-D.ietf-6man-rfc4291bis
Date: Thu, 9 Mar 2017 11:31:30 -0800
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To: Philip Homburg <>
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Hi Philip,

This is just a brief response that I believe goes straight to your argument.

On Mar 9, 2017, at 10:30, Philip Homburg <> wrote:
> Currently RFC 4291 says (and this is still in rfc4291bis-07):
> "Interface identifiers in IPv6 unicast addresses are used to identify
> "interfaces on a link.  They are required to be unique within a subnet prefix.
> It doesn't say anything that the concept of interface identifier is only
> related to stateless address configuration.

That’s because interface identifiers are not just for stateless address configuration. They’re for all forms of address configuration, whether SLAAC, DHCPv6 or manual. In all cases, they are required by RFC 4291 and predecessors to have the uniqueness properties first introduced in RFC 2513 and carried forward into I-D.ietf-6man-rfc4291bis today. The bits following any other form of routing prefix, including on-link prefixes, are not required to have any such uniqueness properties, and they never have been.

--james woodyatt < <>>