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

["Brzozowski, John" <John_Brzozowski () Cable Comcast com>]

On 11/28/11 10:29 AM, "Ray Soucy" <rps () 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 () 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/