European ISP enables IPv6 for all?

Iljitsch van Beijnum iljitsch at
Wed Dec 19 11:11:58 UTC 2007

On 19 dec 2007, at 10:16, Mikael Abrahamsson wrote:

> I am actually more concerned with the CPE problem and how to make  
> autoconfiguration work for end users.

> For instance, should we assign /64 to end users and have them do  
> whatever they need (subnet to /80 if they need more than one network)?

Subnets that aren't /64 don't support autonegotiation so you can't  
really subnet a /64 in practice. This means that you should probably  
give your customers something bigger, like a /64, a /56 or even a /48.  
(Yes, we have enough address space for a /48 per customer.)

The tricky part is provisioning a subnet to a customer. There is a  
good protocol for that: DHCPv6 prefix delegation. But there aren't any  
CPEs on the market that support this. (If it wasn't for Apple's  
Airport Extreme base station and a few somewhat expensive and hard to  
configure Cisco boxes you could argue that there aren't any IPv6- 
capable CPEs commercially available in the first place.)

> We need to provision routes in whatever routers connect to  
> customers, which I guess is the FIB/RIB-problem mentioned above?

Don't think so. As long as you don't let your customers take their  
address space with them when they move you can aggregate customer  
space in your network (you can even waste some address space for that  
without complaints from ARIN) so in practice your IPv6 routing tables  
will probably be smaller than their IPv4 counterparts.

> Is there general agreement that IPv6 requires a router at the  
> customer prem to scale (ISP doesn't want to know what the end user  
> devices are)?

The alternative is having your device act as the default gateway in  
your customer's LAN, which more or less means you need to have a  
separate subnet/VLAN per customer, which is usually not the best way  
to go in larger setups. Don't expect to be doing much with DHCP for  
IPv6, though, most stuff that's out there today doesn't support it and  
you still need router advertisements because DHCPv6 doesn't tell you  
your default gateway.

> Also, is it ok to statically assign /64 to end user or should end  
> user be able to switch addresses (some like dynamic IPs because it's  
> not persistant over time and like the "privacy" you get by changing  
> IP all the time).

Customers can already randomize the lower 64 bits of their address so  
there is some level of privacy. In a prefix delegation system I would  
probably make things such that customers get the same addresses for  
some time (a few months) but I get to change their prefix if/when I  
want to.

> I haven't been able to find a BCP regarding the end user equipment  
> and how to configure it, does anyone have any pointers?

Unfortunately, there is no industry-wide consensus on how CPEs and ISP  
equipment should interact for IPv6, so it's probably not possible at  
this point in time to make a CPE that will completely autoconfigure  
unless you stick to 6to4 tunneling which gets the job done but is less  
than optimal because it needs public gateways.

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