Sorry for the double post. From re-reading the thread it doesn't sound like you might want ULA at all. The mindset of using RFC1918 space, throwing everything behind a NAT box, and not having to re-configure systems when you change ISP doesn't exist in IPv6. There is no IPv6 NAT (yet). If you wanted to setup an "island" of IPv6 that would never talk to the Internet, then you could use ULA, but that would only be needed if you plan on routing between LANs. Remember that by default every IPv6 host has a link-local address allowing it to talk to any directly connected hosts without configuration. So if you're simply looking for some sort of ad-hoc network, it's likely already there. As much as I hate NAT and want to see it go away. I think the biggest transition mechanism for people to get online with IPv6 will be some sort of appliance that does NAT of global IPv6 addresses to private IPv4 addresses to keep all the people living in the NAT world from having to redesign their networks. It's ugly, but its the path of least resistance and that's likely what will happen when we see IPv6 become required to do business... at least as a stepping stone. The idea to use multiple PA IPv6 allocations and have multiple GUAs for each host wasn't a bad one. It would certainly make the Internet routing table a lot more stable to not have everyone touching BGP... But they failed to fix DNS in a way that would make it possible. We already have priority for MX records. If we had priority for all records, and resolvers would remember when one was unreachable for a short time, then yes, you could have www.yourdomain.com point to multiple PA GUAs and if one was down users would nicely fail-over to the other. Unfortunately, if you have a host record with multiple AAAAs and one of them is unreachable, it will just mean that for some users the request will time out (as its just doing a round-robin and not trying others when things don't respond). In theory, you could try to get around the limitation by having a TTL of 30 seconds or something on your records, and have a system that would update DNS records when a connection dropped, but that's assuming people aren't deciding to set minimum cache times of their own. I think the best model possible with existing technology that's available is to separate L2 and L3 and use provider redundancy at L2 (multiple ME transport providers to your single, redundant, L3 transit provider). If you need more redundancy that that, you're likely using BGP for IPv4 already, anyway. The real problem never goes away, though. People like the operational control and simplicity that they get with NAT. If the provider goes down, they still work internally, if they have multiple providers, the internal network doesn't care which is active, and if they need to host services, they usually go with a hosting company off-site. I really don't think it will be long before we see some magic IPv6 NAT boxes start to pop up, whether or not standards exist for them, and it will be and ugly nightmare. IPv6 is simple enough for larger networks (like universities and governments) but very little attention has been giving to the SMB community and their needs with IPv6. On Thu, Oct 21, 2010 at 7:33 AM, Ray Soucy <rps@maine.edu> 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.
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.
On Wed, Oct 20, 2010 at 5:48 PM, Jeroen van Aart <jeroen@mompl.net> 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).[12] 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.
Thanks, Jeroen
-- http://goldmark.org/jeff/stupid-disclaimers/ http://linuxmafia.com/~rick/faq/plural-of-virus.html
-- Ray Soucy
Epic Communications Specialist
Phone: +1 (207) 561-3526
Networkmaine, a Unit of the University of Maine System http://www.networkmaine.net/
-- Ray Soucy Epic Communications Specialist Phone: +1 (207) 561-3526 Networkmaine, a Unit of the University of Maine System http://www.networkmaine.net/