I've been using IPv6 for many years now, but it wasn't until I switched ISP recently (and with that, from 6to4 to 6rd) that I found out that stateless autoconfiguration only works on /64 subnets. I had always assumed that it worked on subnets of arbitrary prefix length.
This took me quite a bit by surprise, and I must admit I don't quite understand the further implications of it. In particular, the following questions arise for me:
- Is stateless autoconfiguration supposed to be the default method for interface initialization, or is DHCPv6 supposed to be used in most places?
- If the latter, then what is stateless autoconfiguration supposed to be used for?
- If the former, does that mean that "all" subnets are supposed to be /64? Why would one want to waste all that address space on "terminal" subnets? Is a network administrator not supposed to be able to subdivide his networks further?
In my particular case, I have a few different physical subnets beyond my router, so when I had my /48 6to4 prefix, I divided it in a couple of /64 subnets, which is why autoconfiguration always worked for me. Now, with 6rd, I just get a /64 prefix instead, which I then have to divide into something small than /64, clearly (I use /48 in practice). Am I not "supposed" to be able to further subdivide a 6rd prefix, or what is the matter here?
If this question looks confrontational, rest assured that is not the intention. I'm just a bit confused and I'd like to understand the intentions.