On Tue, Nov 24, 2015 at 6:34 PM, Baldur Norddahl <baldur.nordd...@gmail.com> wrote: > > DHCPv6-PD allows multiple PD requests. But did anyone actually implement > that? I am not aware of any device that will hand out sub delegations on > one interface, notice that it is out of address space and then go request > more space from the upstream router (*). > > DHCPv6-PD allows size hints, but it is often ignored. Also there is no > guidance for what prefix sizes you should ask for. Many CPEs will ask for > /48. If you got a /48 you will give out that /48 and then not honor any > further requests, because only one /48 per site is allowed. If you are an > ISP that gives out /48 and your customers CPE asks for a /56 you will still > ignore his size hint and give him /48.
Or, worse, the ISP's DHCPv6 server honors the new request and issues the larger prefix, but refuses to route it. Ran into that myself when I replaced my home CPE router, and changed the prefix hint to ask for a /60 block (expanded from /64) at the same time. That made for a frustrating few days without IPv6 service, waiting for my original delegation to expire. (Tech support, of course, had no clue and blamed my router.) In retrospect I should have perhaps had my original CPE generate a DHCP release message for that prefix before disconnecting it. But I won't be the last person to fail to generate that. -Brian