Assigning IPv6 /48's to CPE's?

michael.dillon at bt.com michael.dillon at bt.com
Thu Jan 3 14:59:05 UTC 2008


> > I'd rather push for /48 and have people settle on /56 than push for 
> > /56 and have people settle on /64.
> 
> Again, why the hang-up on 8 bit boundaries?

Look, why are we arguing about this? Why not split
the difference? If /48 is too big and /64 is too small,
let's go halfway and use /56, OK?

This has the advantage that it is on a 4 bit nibble 
boundary which makes it the boundary between network
and interface much clearer in writing
2001:3ff3:effe:1200::0/56 
If you wrote 2001:3ff3:effe:12a0::0/56 then I would 
immediately see that there are too many bits in the network
portion. It also avoids a messy situation with reverse
DNS delegations.

In the end, the decision had to be made to but the boundary
somewhere, and with 16 bits to be divided plus the need to
use 4-bit boundaries, the choices were (4,12), (8,8), and
(12,4). Split the difference was the least objectionable.

ARIN's decision on this boundary point has since been accepted
by two other RIRs, so it seems to be community consensus now.

--Michael Dillon



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