Slashdot: UK ISP PlusNet Testing Carrier-Grade NAT Instead of IPv6

Wed Jan 16 20:15:21 UTC 2013

Hi,

> If I have calculated the netmasks right that would mean to set aside:
> 
> 2001:0DB8:6440::/42
> 
> for the use of 6rd service:
> 
> 2001:0DB8:6440:0000::/64 = 100.64.0.0
> ....
> 2001:0DB8:647F:FFFF::/64 = 100.127.255.255

You probably should add a few extra bits for subnetting behind the 6rd CPE. Delegating one /64 would be annoying as more and more CPEs have separate home/office/guest networks. Giving a /56 to each customer would be good and would only take an IPv6 /34 to map from 100.64.0.0/10. That is a quarter of the smallest IPv6 allocation an ISP can get.

ISPs can get plenty of IPv6 address space these days if they need it. Smaller ISPs don't need to map the whole 100.64.0.0/10, they could just start with 100.64.0.0/16 for example, which would only take a /40 to give every customer a /56. More blocks can always be added to the 6rd setup later.

Cheers,
Sander