Hi John,The specification reserves FE80::/10 for any link-local address format. The only currently used instantiation is the FE80::/64 prefix. In other words, a new RFC could define alternative formats for the internal 54 bits underneath the FE80::/10 prefix.
Regards, Brian On Jul 11, 2006, at 12:11, John Spence wrote:
Reading RFC 4291, I am not 100% clear on the format for link-local addresses. In some places the document specifies “fe80::/10”, which I read as “the first ten bits must be 1111 1110 10, the remaining 54 bits can be anything, up to the /64 bit boundary . Later in the document I see this:2.5.6. Link-Local IPv6 Unicast Addresses Link-Local addresses are for use on a single link. Link-Local addresses have the following format: | 10 | | bits | 54 bits | 64 bits | +----------+-------------------------+----------------------------+ |1111111010| 0 | interface ID |Which I read as “the first 64 bits are always fe80::”, but then I would think we’d write that as “fe80::/64”.So, do those middle 54 bits have to be zero, or can they be anything? Thanks for any insight. John Spence, Command Information [EMAIL PROTECTED] -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
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