John,
On Jul 11, 2006, at 12:11 PM, ext John Spence wrote:
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?
They must be zero.
The prefix that identifies IPv6 link local addresses is FE80::/10 as
defined in Section 2.4. All of the addresses under this prefix have
link-scope.
The format of link local addresses is defined in Section 2.5.6 and it
requires that there be 54 bits of zeros between the prefix and the
Interface ID.
In the future we could define some other types of address that have
link-scope and these would also be in the FE80::/10 prefix, but now
there is only one type.
Bob
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