[AusNOG] another ipv6 Q

[Tony]

On Thu, 03 Jul 2014 14:30:07 +1000, Jeroen Massar <jeroen at massar.ch> wrote:
>
> Oh and yes, it will be a lot of fun when some large company is going to
> split and then have to split up their IPv6 address space, somebody will
> be renumbering a lot of hosts... ;)

Which raises a question I've been wondering about (and pardon my ignorance  
if it's obvious, I'm still coming to grips with IPv6).

In the IPv4 world the following happens:
* as an SP we have IPv4 address space from APNIC
* a customer of ours is using IPv4
* customer uses RFC1918 space on their internal/private network
* we allocate a /29 to customer firewall that is globally routable
* customer does NAT for traffic in/out the firewall for global  
reachability (via the /29)

All pretty standard and fairly well understood.

My understanding of one of the design principles of IPv6 is that NAT will  
go (hooray !) and every device will have a globally unique IP address. I  
assume this is still correct ?

That being the case in the scenario I've outlined above the customer needs  
to get IPv6 space from "somewhere". The suggestion is that they would get  
it from their SP (ie. us) which I have no problem with. So it then looks  
like:
* We allocate a /48 (out of our /32 that we have from APNIC) to customer
* customer splits this up as they see fit (hopefully following some rules  
as to how they allocate subnets)
* customer gives devices an IPv6 address out of this /48 on all their  
devices
* all customer devices are now globally addressable

So what happens when said customer changes to another SP ? Do they then  
have to renumber everything ? The alternative could be the customer  
approaches the LIR and gains a /48 from the LIR, but wouldn't you then  
just have every company in the world with their own /48 which would just  
cause issues with aggregation and routing table size ?

I know there is SLAAC & DHCPv6, so would it simply be the case of what  
would happen now if a customer needed to change the RFC1918 subnet they  
were using internally ? In the IPv4 world, this would mean changing DHCP  
scopes, then changing anything that is manually set ?

I'm just curious as for anyone who isn't able to get their own globally  
unique space from a LIR then does the IPv6 world force them to renumber  
their entire network every time they change providers and have new IPv6  
addressing ? Right now changing providers means getting a new IPv4/29 for  
the outside of the firewall and perhaps changing a few NAT rules (and  
updating DNS), all of the internal IP's on devices get to stay the same  
(due to the NAT).


Thanks,
Tony.