On 22/09/2011 9:43 PM, Per Johansson wrote:
22 sep 2011 kl. 12:14 skrev Michael Stefaniuc:
Wow! /66? And that works? While the standard allows for that you "should use /64" which everybody and his dog read it as that is the only thing that needs to work and the only thing that get tested. IPv6 brings back the class-full thinking which everybody has to painfully unlearn once IPv6 catches on...
"Safe" prefix length (especially if involving client devices) are: /64 - LAN /126 and /127 - point to point /128 - host routes
RFC3513 is quite more strict than "should":
All global unicast addresses other than those that start with binary 000 have a 64-bit interface ID field (i.e., n + m = 64), formatted as described in section 2.5.1. Global unicast addresses that start with binary 000 have no such constraint on the size or structure of the interface ID field.
(2001:: has the binary prefix 001). So this might very well be the problem.
If I understand that correctly, if the interface has a hardware address (48-bit MAC or 64-bit EUI), then the interface ID should be constructed from that address.
Of course, if you are the administrator of the 2001:888:2000:38::/64 block, then you can assign Scope-Local Interface IDs as you see fit, just as everyone else does, and as allowed in RFC3513 2.5.1 - however, the RFCs say the subnet mask needs to be /64.