subnet prefix length > 64 breaks IPv6?

Alexandru Petrescu alexandru.petrescu at
Sat Dec 24 11:16:07 UTC 2011

Le 24/12/2011 11:58, Karl Auer a écrit :
> On Sat, 2011-12-24 at 15:37 +0530, Glen Kent wrote:
>> Ok. So does SLAAC break with masks>  64?
> "Break" is not the right word. SLAAC only works with /64, But that is
> by design.

SLAAC only works with /64 - yes - but only if it runs on Ethernet-like
Interface ID's of 64bit length (RFC2464).

SLAAC could work ok with /65 on non-Ethernet media, like a
point-to-point link whose Interface ID's length be negotiated during the
setup phase.

Other non-64 Interface IDs could be constructed for 802.15.4 links, for
example a 16bit MAC address could be converted into a 32bit Interface
ID.  SLAAC would thus use a /96 prefix in the RA and a 32bit IID.

IP-over-USB misses an Interface ID altogether, so one is free to define
its length.


> Regards, K.

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