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

Mon Nov 28 22:33:41 UTC 2011

On 11/28/11 10:29 AM, "Ray Soucy" <rps at maine.edu> wrote:

>It's a good practice to reserve a 64-bit prefix for each network.
>That's a good general rule.  For point to point or link networks you
>can use something as small as a 126-bit prefix (we do).
[jjmb] for point to point I agree with this point.  If a /64 is reserved
one has greater flexibility as far as what is configured on the interfaces.
>
>When it comes to implementation, though, it's not as simple as a yes
>or no answer.
>
>The actual use of 64-bit prefixes is not something I would currently
>recommend for large-scale deployments due to the denial of service
>attack vector it opens up (neighbor table exhaustion).
[jjmb] not sure I agree, this depends on where the prefix is being
installed in the network.
>
>Not using 64-bit prefixes tosses SLAAC out the window; but for many
>networks SLAAC may not be desirable anyway due to the lack of control
>it presents.
>
>Once vendors come out with routers that are able to protect against
>neighbor table exhaustion, moving to a 64-bit prefix (which you
>hopefully reserved) will allow you to be more flexible in what
>addressing methods are used.
>
>On Mon, Nov 28, 2011 at 6:37 AM, Dmitry Cherkasov <doctorchd at gmail.com>
>wrote:
>> Hello everybody,
>>
>> It is commonly agreed that /64 is maximal length for LANs because if
>> we use longer prefix we introduce conflict with stateless address
>> autoconfiguration (SLAAC) based on EUI-64 spec. But  SLAAC is not used
>> in DOCSIS networks. So there seems to be no objections to use smaller
>> networks per cable interfaces of CMTS. I was not able to find any
>> recommendations anywhere including Cable Labs specs for using
>> prefixes not greater then /64 in DOCSIS networks. Some tech from ISP
>> assumed that DHCPv6 server may generate interface ID part of IPv6
>> address similarly to EUI-64 so MAC address of the device can easily be
>> obtained from its IPv6 address, but this does not seem like convincing
>> argument. What do you think?
>>
>>
>> Dmitry Cherkasov
>>
>>
>
>
>
>-- 
>Ray Soucy
>
>Epic Communications Specialist
>
>Phone: +1 (207) 561-3526
>
>Networkmaine, a Unit of the University of Maine System
>http://www.networkmaine.net/
>