nanog mailing list archives
Re: subnet prefix length > 64 breaks IPv6?
From: Owen DeLong <owen () delong com>
Date: Tue, 3 Jan 2012 14:36:54 -0800
On Dec 24, 2011, at 6:48 AM, Glen Kent wrote:
SLAAC only works with /64 - yes - but only if it runs on Ethernet-like Interface ID's of 64bit length (RFC2464).Ok, the last 64 bits of the 128 bit address identifies an Interface ID which is uniquely derived from the 48bit MAC address (which exists only in ethernet).
Not exactly. Most media have some form of link-layer addressing. For Firewire, it's native EUI-64. For Ethernet, it's EUI-48 MAC addresses. For token ring, I believe there are also EUI-48 addresses. For FDDI (Remember FDDI?) I believe it was EUI-48 addresses. ATM and Frame Relay also have EUI addresses built in to their interfaces (though I don't remember the exact format and am too lazy to look it up at the moment).
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.If we can do this for a p2p link, then why cant the same be done for an ethernet link?
I'm not so sure the statement above is actually true. Owen
GlenOther 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. AlexRegards, K.
Current thread:
- Re: subnet prefix length > 64 breaks IPv6? Owen DeLong (Jan 03)
- Re: subnet prefix length > 64 breaks IPv6? Alexandru Petrescu (Jan 04)
- <Possible follow-ups>
- Re: subnet prefix length > 64 breaks IPv6? Owen DeLong (Jan 03)
- Re: subnet prefix length > 64 breaks IPv6? Karl Auer (Jan 03)
- Re: subnet prefix length > 64 breaks IPv6? Joel jaeggli (Jan 04)
- Re: subnet prefix length > 64 breaks IPv6? Bjørn Mork (Jan 07)
- Re: subnet prefix length > 64 breaks IPv6? sthaug (Jan 07)