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/