Network Working Group S. Krishnan
Request for Comments: 5453 Ericsson
Category: Standards Track February 2009
Reserved IPv6 Interface Identifiers
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RFC 5453 Reserved IPv6 Interface Identifiers February 2009
Table of Contents
1. Introduction
An IPv6 unicast address is composed of two parts: a subnet prefix and an interface identifier (IID) that identifies a unique interface within the subnet prefix. The structure of an IPv6 unicast address is depicted in "IPv6 Addressing Architecture" [RFC4291] and is replicated here for clarity.| n bits | 128-n bits | +-------------------------------+---------------------------------+ | subnet prefix | interface ID | +-------------------------------+---------------------------------+Figure 1: IPv6 Unicast Address Format
1.1. Applicability
This document applies only to interface identifiers that are formed in the modified EUI-64 format as defined in Appendix A of [RFC4291]. All other types of interface identifiers are out of its scope.
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RFC 5453 Reserved IPv6 Interface Identifiers February 2009 1.2. Requirements NotationThe key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
2. Issues with Reusing Reserved Interface Identifiers
Let us assume a node comes up with an interface identifier that has been reserved for use in some other capacity, e.g., an IPv6 node that uses temporary IPv6 addresses [RFC4941] comes up with an IID of fdff:ffff:ffff:ffff. This node will receive requests from all nodes that are requesting a service from a Mobile IPv6 home agent since the above-mentioned interface identifier has been reserved in [RFC2526] to serve as a MIPv6 home agent's anycast address. At best, this is an annoyance to the node that came up with this address. At worst, another node on the link would be denied service and may not look for other methods of acquiring a home agent. Thus, such reserved interface identifiers MUST NOT be used for autonomous autoconfiguration or for managed address configuration.
2.1. Possible Solutions
There are two possible ways to go about avoiding usage of these reserved interface identifiers. One of them would be to add a normative reference to each specification that reserves an interface identifier. The other would be to create an IANA registry for such interface identifiers. There are two disadvantages to the normative reference approach. Firstly, this approach does not scale well because the number of such specifications that would need to be updated is large. Secondly, the maturity level of the document reserving the IID might be lower than the one prohibited from using it; this will cause a downward reference problem. Therefore, the better solution is to create an IANA registry for this purpose.
3. IANA Considerations
This document creates an IANA registry for reserved IPv6 interface identifiers. Initial values for the reserved IPv6 interface identifiers are given below.
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RFC 5453 Reserved IPv6 Interface Identifiers February 2009
+-----------------------------------------+-------------------------+
| Interface Identifier Range | Description |
+-----------------------------------------+-------------------------+
| 0000:0000:0000:0000 | Subnet-Router Anycast |
| | [RFC4291] |
| | |
| FDFF:FFFF:FFFF:FF80-FDFF:FFFF:FFFF:FFFF | Reserved Subnet Anycast |
| | Addresses[RFC2526] |
+-----------------------------------------+-------------------------+
Table 1: Current Assignments
4. Acknowledgements
The author would like to thank Alain Durand, Alex Petrescu, Bernie Volz, Bob Hinden, Christian Huitema, Fred Templin, Jordi Palet Martinez, Pekka Savola, Remi Denis-Courmount, Tim Enos, Ed Jankiewicz, Brian Carpenter, Alfred Hoenes, Jari Arkko, Pasi Eronen, Tim Polk, Lars Eggert, Derek Atkins, and Robert Sparks for reviewing this document and suggesting changes.
5. Security Considerations
By utilizing one of the reserved interface identifiers, an IPv6 node might receive requests that it is not authorized to receive. Information that creates or updates a registration in this registry needs to be authenticated and authorized by the IANA based on the instructions set forth by [RFC5226].
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RFC 5453 Reserved IPv6 Interface Identifiers February 2009 6. References 6.1. Normative References[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
6.2. Informative References
[HBA] Bagnulo, M., "Hash Based Addresses (HBA)", Work in
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RFC 5453 Reserved IPv6 Interface Identifiers February 2009 Appendix A. List of Potentially Affected RFCsImplementations of the following RFCs need to be aware of the reserved interface identifier ranges when they allocate new addresses. Future revisions of these RFCs should ensure that this is either already sufficiently clear or that the text is amended to take this into account.
