2013-02-11  23:51, Usman Latif <osma...@yahoo.com> :

> Hi Remi,
> 
> 
> 
> On 11/02/2013, at 9:13 PM, Rémi Després <despres.r...@laposte.net> 
>> ...
>>> So if I understand it correctly, if a PE-CE link already has a /127 prefix 
>>> assigned to it- and we wanted to use the CE as a 4rd CE, we'll have to 
>>> assign an additional IPv6 prefix to the CE with 64-bit IIDs?
>>> 
>>> Pls share little detail with me in a scenario where a SP already has /127 
>>> with CEs and 4rd is needed from the CE
>> 
>> According to RFC 6164, /127 prefixes are used ONLY on inter-router link. 
>> They cannot be used as customer-site IPv6 prefixes which, to comply with 
>> https://tools.ietf.org/html/rfc4291#section-2.5.1, MUST permit 64-bit IIDs. 
>> 
>> Each 4rd CE MUST therefore be delegated at least one IPv6 prefix having at 
>> most 64 bits (this doesn't depend on its WAN link having or not a /127). 
>> 
>> RD
> 
> 
> Yes 6164 is only for inter-router links
> I was under the impression that 4rd CE might use the WAN IPv6 address for 
> stateless tunnelling of IPv4 inside IPv6
> Maybe this was a misunderstanding(?)

In the 4rd specification, CE IPv6 prefixes are at most /64.
See Figure 5 in particular:

   +----------+---+-+-+------+---+     +--------------+-+-+------+---+
   |CE v6 prfx| 0 |V|0|v4 add|CNP|     |BR IPv6 prefix|V|0|v4 add|CNP|
   +----------+-|-+-+-|+-----+---+     +--------------+-+-+------+---+
   :   =<64   : | :8:8:  32  :16 :     :      64      :8:8:  32  :16 :
                |
          Padding to /64

RD



 
> Or is it really upto the operator whether he wants to leverage the CE WAN 
> IPv6 prefix or the allocated IPv6 prefix routed to the CE site
> If the CE WAN happens to be a /64 prefix, could the 4rd leverage that?
> What is the recommendation there
> 
> 
> Regards,
> Usman
> 
> 
> 

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