it only breaks the auto configure crap which you don't want to use anyway. (unless you want to have any computer on your network be able to tell any other computer "oh hai i'm a router, please route all your packets through me so i can intercept them" and/or flood its route table ;) we use all kinds of things from /126'es to /112 (but hardly any /64 crap) works perfectly fine. as long as its nibble aligned (for other reasons ;) -- Greetings, Sven Olaf Kamphuis, CB3ROB Ltd. & Co. KG ========================================================================= Address: Koloniestrasse 34 VAT Tax ID: DE267268209 D-13359 Registration: HRA 42834 B BERLIN Phone: +31/(0)87-8747479 Germany GSM: +49/(0)152-26410799 RIPE: CBSK1-RIPE e-Mail: sven@cb3rob.net ========================================================================= <penpen> C3P0, der elektrische Westerwelle http://www.facebook.com/cb3rob ========================================================================= Confidential: Please be advised that the information contained in this email message, including all attached documents or files, is privileged and confidential and is intended only for the use of the individual or individuals addressed. Any other use, dissemination, distribution or copying of this communication is strictly prohibited. On Sat, 24 Dec 2011, Glen Kent wrote:
Hi,
I am trying to understand why standards say that "using a subnet prefix length other than a /64 will break many features of IPv6, including Neighbor Discovery (ND), Secure Neighbor Discovery (SEND) [RFC3971], .. " [reference RFC 5375]
Or "A number of other features currently in development, or being proposed, also rely on /64 subnet prefixes."
Is it because the 128 bits are divided into two 64 bit halves, where the latter identifies an Interface ID which is uniquely derived from the 48bit MAC address.
I am not sure if this is the reason as this only applies to the link local IP address. One could still assign a global IPv6 address. So, why does basic IPv6 (ND process, etc) break if i use a netmask of say /120?
I know that several operators use /120 as a /64 can be quite risky in terms of ND attacks. So, how does that work? I tried googling but couldnt find any references that explain how IPv6 breaks with using a netmask other than 64.
Glen