Date: Sun, 27 Jun 2021 10:36:33 -0600 From: Kurt Buff <kurt.buff@gmail.com> To: Doug Hardie <bc979@lafn.org> Cc: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Re: IPv6 Sub Nets Message-ID: <CADy1Ce5ceBL3Vh2=CKf9y_DyjhMi4GbSeGnht5wq-Mkh02NxjA@mail.gmail.com> In-Reply-To: <5B552F4B-0BA3-4962-A131-AB352A88980C@sermon-archive.info> References: <056639D1-32A2-4DAF-A6F8-C8743F691EAD@sermon-archive.info> <B707A230-78B3-4BF8-B7C0-350E48EAEF04@cryptomonkeys.org> <5B552F4B-0BA3-4962-A131-AB352A88980C@sermon-archive.info>
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On Sat, Jun 26, 2021 at 8:19 PM Doug Hardie <bc979@lafn.org> wrote: > > > -- Doug > > > On 26 June 2021, at 19:02, Louis Kowolowski <louisk@cryptomonkeys.org> = wrote: > > > > On Jun 26, 2021, at 8:25 PM, Doug Hardie <bc979@lafn.org <mailto:bc979@= lafn.org>> wrote: > >> > >> I am trying to setup an IPv6 environment. There is a primary router (= A) that receives a /48 prefix via DHCP6 from the ISP. That router configur= es itself properly via dhcp6c. It also creates 2 LAN /64 prefixes and crea= tes EUI-64 addresses on the two LAN interfaces. One of those interfaces is= connected to a second router (B), among other devices. The B router recei= ves the prefix via SLAAC and creates its own EUI-64 address. However, that= router needs to create a smaller subnet, /72, and distribute it to the dev= ices on that LAN. I have not been able to figure out how to make that happ= en. > >> > >> Clearly, manual configuration would work, but the prefix received from= the ISP can change which would raise havoc with the network. I suspect th= at dhcp6s needto be run alongside dhcp6c on router B and then the other dev= ices run dhcp6c. However, I don't see how to get the prefix that dhcp6c re= ceives on router B to the dhcp6s process on router B. I believe I am missi= ng something, but haven't been able to find it. Thanks, > >> > > Speaking generally > > > > First: I believe you=E2=80=99re looking to do DHCP prefix delegation (d= hcp-pd) where you designate a prefix to be used further down the line. > > That is what is being used between the ISP and router A. However, router= Bs dhcp6s needs to find that prefix. About all I have come up with is som= e sort of script which monitors the network addresses and then updates dhcp= 6s.conf and restarts dhcp6s. Not very elegant though. > > > Second: There are valid use cases for prefixes smaller than /64, but th= ey are not best practice, and you will likely find software that doesn=E2= =80=99t work for them (examples I=E2=80=99ve found include PDUs hardcoding = /64, dhcp not working on prefixes smaller than /64. examples of things I=E2= =80=99ve seen that do work: point-to-point links on network equipment using= /126 or /127). > > > > -- > > Louis Kowolowski louisk@cryptomonkeys.or= g <mailto:louisk@cryptomonkeys.org> > > Cryptomonkeys: http://www.cryptomonke= ys.com/ <http://www.cryptomonkeys.com/>; On one of the ipv6 lists to which I subscribe (ipv6-ops), there have been discussions of renumbering by ISP and the difficulties it's posing. I don't have a link handy, and I don't think the discussion reached a conclusion, but you might glean some useful insights from it. Kurt
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