On Mar 5, 2011 9:50 AM, "Scott Schmit" <i.g...@comcast.net> wrote: > > On Sat, Mar 05, 2011 at 10:59:25AM +0800, Yu Hua bing wrote ipv6: > > >RFC4291 > > > 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 | > > +----------+-------------------------+----------------------------+ > > > > I have a question: If the front 10 bits of one IPv6 address is FE80 and the middle 54 bits is not zero, is it link-local address? > > Increasing the puzzle, while the text above would imply that if the > middle 54 bits are not zero, it's not link-local, but if you look at > http://www.iana.org/assignments/ipv6-address-space/ipv6-address-space.xml, > you will see that IANA has allocated fe80::/10 to "Link Local Unicast". > This lends weight to the interpretation that it's the 10 bits that makes > it a link-local address. Otherwise, they should only have allocated > fe80::/64 for that purpose. > > I'm leaning toward the interpretation being "if you're in fe80::/10, > you're link local, but addresses outside fe80::/64 are reserved."
Exactly right, IMHO. Link local unicast (generic, that is - any link-scoped uni) vs link local addresses (specific, the ones required* to be on an interface) /TJ
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