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Re: IPv6 fc00::/7 — Unique local addresses
- From: Ray Soucy
- Date: Thu Oct 21 08:23:38 2010
I guess my point is that as soon as you introduced the human element
into ULA with no accountability, it became a lost cause. People can't
be trusted to respect the RFC once they know it's non-routed address
space, and I suspect most won't. Just like countless vendors still
use 18.104.22.168 as a baked-in management address even though there was
never a time when that was allowed. It was a nice idea, but as soon
as you let people "choose" the "random" number, well... there you go.
At least if you stay within the FD space we have a chance at using FC
On Thu, Oct 21, 2010 at 7:47 AM, Owen DeLong <email@example.com> wrote:
> On Oct 21, 2010, at 4:33 AM, Ray Soucy wrote:
>> For for all intents and purposes if you're looking for RFC1918 style
>> space in IPv6 you should consider the block FD00::/8 not FC00::/7 as
>> the FC00::/8 space is reserved in ULA for assignment by a central
>> authority (who knows why, but with that much address space nobody
>> really cares).
>> People may throw a fit at this, but as far as I'm concerned FD00::/8
>> will never leave the edge of our network (we null route ULA space
>> before it can leak out, just like you would with RFC1918 space). So
>> you can pretty much use it has you see fit. If you want to keep your
>> ULA space short there is nothing stopping you from using something
>> like FD00::1 as a valid address.
> I have no problem with that. My concern is that people will use FD00::/8
> space in OTHER ways, and, since it has potential uniqueness if you
> follow the RFC, it has greater potential for undesired success than
>> You could embed your ASN into it or some other identifier if you want
>> to avoid conflicts with other non-routed address space which should
>> never enter or leave your network from the outside, but I'm just not
>> seeing the practical application for this.
> That only avoids conflicts if everyone within the networks to which
> you may communicate uses the same system of uniqueness.
> Think beyond today to the future possibility of M&A of other companies
> also using ULA, etc.
>> On Wed, Oct 20, 2010 at 5:48 PM, Jeroen van Aart <firstname.lastname@example.org> wrote:
>>> <IPv6 newbie>
>>> According to http://en.wikipedia.org/wiki/IPv6_address#Special_addresses an
>>> fc00::/7 address includes a 40-bit pseudo random number:
>>> "fc00::/7 — Unique local addresses (ULA's) are intended for local
>>> communication. They are routable only within a set of cooperating sites
>>> (analogous to the private address ranges 10/8, 172.16/12, and 192.168/16 of
>>> IPv4). The addresses include a 40-bit pseudorandom number in the routing
>>> prefix intended to minimize the risk of conflicts if sites merge or packets
>>> are misrouted into the Internet. Despite the restricted, local usage of
>>> these addresses, their address scope is global, i.e. they are expected to be
>>> globally unique."
>>> I am trying to set up a local IPv6 network and am curious why all the
>>> examples I come accross do not seem to use the 40-bit pseudorandom number?
>>> What should I do? Use something like fd00::1234, or incorporate something
>>> like the interface's MAC address into the address? It'd make the address
>>> quite unreadable though.
>> Ray Soucy
>> Epic Communications Specialist
>> Phone: +1 (207) 561-3526
>> Networkmaine, a Unit of the University of Maine System
Epic Communications Specialist
Phone: +1 (207) 561-3526
Networkmaine, a Unit of the University of Maine System