IPv6 prefixes longer then /64: are they possible in DOCSIS networks?

Tue Nov 29 12:58:15 UTC 2011

Thanks to everybody participating in the discussion.
I try to summarize.

1) There is no any obvious benefit of using longer prefixes then /64
in DOCSIS networks yet there are no definite objections to use them
except that it violates best practices and may lead to some problems
in the future

2) DHCPv6 server can use any algorithm to generate interface ID part
of the address, and EUI-64 may be just one of them that can be useful
for keeping correspondence between MAC and IPv6 addresses. Yet if we
use EUI-64 we definitely need to use /64 prefix

3) Using /64 networks possesses potential security threat related to
neighbor tables overflow. This is wide IPv6 problem and not related to
DOCSIS only

There were also notes about address usage on link networks. Though
this was out of the scope of original question it is agreed that using
/64 is not reasonable here. BTW, RFC6164 (Using 127-Bit IPv6 Prefixes
on Inter-Router Links) can be mentioned here.

Dmitry Cherkasov

2011/11/29 Dmitry Cherkasov <doctorchd at gmail.com>:
> Tore,
>
> To comply with this policy we delegate at least /64 to end-users
> gateways. But this policy does not cover the network between WAN
> interfaces of CPE and ISP access gateway.
>
> Dmitry Cherkasov
>
>
>
> 2011/11/29 Tore Anderson <tore.anderson at redpill-linpro.com>:
>> * Dmitry Cherkasov
>>
>>> I am determining technical requirements to IPv6 provisioning system
>>> for DOCSIS networks and I am deciding if it is worth to restrict user
>>> to use not less then /64 networks on cable interface. It is obvious
>>> that no true economy of IP addresses can be achieved with increasing
>>> prefix length above 64 bits.
>>
>> I am not familiar with DOCSIS networks, but I thought I'd note that in
>> order to comply with the RIPE policies, you must assign at least a /64
>> or shorter to each end user:
>>
>> http://www.ripe.net/ripe/docs/ripe-523#assignment_size
>>
>> --
>> Tore Anderson
>> Redpill Linpro AS - http://www.redpill-linpro.com