Chris Siebenmann
Current status: reading about IPv6 address allocation plans and wondering if there are reasons to give any of our existing IPv4 subnets something larger than a /64.
(Our subnet firewalls don't run routing protocols so it's hard to see how multiple interior IPv6 networks on a subnet would work, even if people wanted to give, eg, their VM cluster an entire /64 for itself. Maybe it'd all work out?)
The Janx Devil
@cks That “give each customer a /64 prefix” thing was the first big IPv6 fight I remember breaking out in V6OPS, because the address architecture originally said “give each customer a whole /48, so they basically never ever need to renumber until they become a transit provider” and CableLabs / Broadband Forum / et al basically said, “Why do we have to give them a whole /48 when we’re just going to renumber them at will and never let them run their own routing domains anyway?”
Some of them compromised and said “okay we’ll give them a /60 or maybe even a /56 if we’re especially generous” and then sabotaged every possible effort to make it possible for their customers to have anything other than a single /64.
Chris Siebenmann
@janxdevil IPv6 scarcity thinking is nowhere near dead, sadly. Our local central networking people started out by suggesting that my entire department would have a /60. I had to break the news to them that we already had more (IPv4) subnets than that.
Chris Siebenmann
@janxdevil DHCP-PD does seem to be close to ideal for the sort of consumer ISP environment descriptions of it make it sound like it was designed for. You delegate the prefix to your customer router cloud, you give each customer a /64 PD delegation, and if the customer gets renumbered some day, well, tough, you never promised them static global IPv6, they should be used to it from IPv4.
The Janx Devil
@cks Reason people use DHCP-PD instead of a real routing protocol is it’s mostly zero human knowledge required for deploying a router for the delegated prefixes. You just plug it into the network, and it gets a prefix and routes for it. All the headaches are with the integration of the DHCP server with the actual routing protocol. This is why CableLabs and other insisted on building it that way, and it’s also why it’s a giant headache and doesn’t work well in any kind of generalized way. (We tried to fix it in the HOMENET working group in IETF, but the effort exploded in the worst kind of IETF stupidity that I still can’t discuss without anesthesia and muscle relaxants.)
Chris Siebenmann
@janxdevil I think we could sort of do that but it'd be a bit awkward and I don't think we'd save anything. We do have one firewall that has a lot of subnets behind it, so in theory it would be a good candidate for a big prefix, but in practice we want to preserve our freedom to move some subnets to their own firewall if necessary (without renumbering things on them).
I guess we could use a prefix for the general firewall plus more specific routes for some.
The Janx Devil
@cks So a reason to hand out more than /64 to a subnet is you plan to delegate prefixes to routers that connect to they subnet. Typically not with a routing protocol, but with DHCP-PD.
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