> I can find many reasons to remove the magic from the U and G bits. I > personally ran into the U/G bit issues in RFC 4380 (Teredo) and RFC 6052 > (IPv4-embedded IPv6 addresses). In both cases, the design would have been > simpler if we had not try to maintain the fiction of the U and G bits. And > CGA could definitely benefit from 2 additional bits of entropy. So this is > not a change "just because."
Fully agreed. Another point in favor of removing the magic: RFC 4291 explicitly says "For all unicast addresses, except those that start with the binary value 000, Interface IDs are required to be 64 bits long and to be constructed in Modified EUI-64 format." but later in the same chapter says "IPv6 nodes are not required to validate that interface identifiers created with modified EUI-64 tokens with the "u" bit set to universal are unique." And indeed, on the routers where I have tried, I am able to configure static IPv6 addresses with no regard to the u/g bits. In other words, any special meaning of the u/g bits is just fiction - there is no enforcement or guarantee of any kind. Steinar Haug, AS 2116 -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
