Hi Owen.
The downside is that it doesn't provide enough bits for certain kinds of auto-topology management that are being considered by CE vendors. I highly recommend /48 instead.
I've seen this claim (you need a /48) from your side several times, but never seen any explanation why a /56 won't work. Is there any requirement that sub-delegations must happen on 8-bit boundaries? AFAICS there is at least nothing in the RFC. Wouldn't for example a nibble boundary work equally well (splitting a /56 into 16 /60s, each containing 16 /64s)? I don't challenge the claim, I'm just trying to understand the rationale behind it. -- Pelle RFC1925, truth 11: Every old idea will be proposed again with a different name and a different presentation, regardless of whether it works.