I believe this was discussed and clarified before, but I could not find any pointer, so let me ask here...
It's regarding the "magic number" of 0xFFFE used in the modified EUI-64 format for the interface identifier of an IPv6 address. According to draft-ietf-ipv6-addr-arch-v4-04.txt (or already-published RFCs), we insert 0xFFFE in the middle of the interface identifier in order to convert an 48-bit MAC address to the modified EUI-64 format: [EUI64] defines a method to create a IEEE EUI-64 identifier from an IEEE 48bit MAC identifier. This is to insert two octets, with hexadecimal values of 0xFF and 0xFE, in the middle of the 48 bit MAC (between the company_id and vendor supplied id). (in APPENDIX A) However, according to [EUI64], we use 0xFFFF (not 0xFFFE) "to create an EUI-64 identifier from a 48bit MAC identifier" for network devices (i.e., MAC-48): To support encapsulation of EUI-48 and MAC-48 values within small subsets of the EUI-64 values, the first four digits of the manufacturer's extension identifier shall not be FFFF16 or FFFE16. Thus, the 64-bit values of the following form are never-assigned EUI-64 values: ccccccFFFEeeeeee(16) (an EUI-48 extension) ccccccFFFFeeeeee(16) (a MAC-48 extension) <==== this one (from http://standards.ieee.org/regauth/oui/tutorials/EUI64.html) My question is whether there was any special reason why the IPv6 addr-arch document specified 0xFFFE. I googled and found a web page saying this is "an error": Confusingly IPv6 -- one of the most prominent standards that uses EUI-64 -- applies these rules inconsistenly. Due to an error in the appendix to the specification of IPv6 addressing, it is currently standard practice in IPv6 to extend MAC-48 addresses (such as IEEE 802 MAC address) to EUI-64 using 'FF-FE' rather than 'FF-FF'; it remains to be seen how this inconsistency will be resolved in the future. (http://www.kingj.com/articles/MAC_address) Is this true, or was there any particular reason for the "confusing" choice? I appreciate any clarification in advance, JINMEI, Tatuya Communication Platform Lab. Corporate R&D Center, Toshiba Corp. [EMAIL PROTECTED] -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
