Date: Sat, 26 Jun 2021 19:18:59 -0700 From: Doug Hardie <bc979@lafn.org> To: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Re: IPv6 Sub Nets Message-ID: <5B552F4B-0BA3-4962-A131-AB352A88980C@sermon-archive.info> In-Reply-To: <B707A230-78B3-4BF8-B7C0-350E48EAEF04@cryptomonkeys.org> References: <056639D1-32A2-4DAF-A6F8-C8743F691EAD@sermon-archive.info> <B707A230-78B3-4BF8-B7C0-350E48EAEF04@cryptomonkeys.org>
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-- Doug > On 26 June 2021, at 19:02, Louis Kowolowski <louisk@cryptomonkeys.org> = wrote: >=20 > On Jun 26, 2021, at 8:25 PM, Doug Hardie <bc979@lafn.org = <mailto:bc979@lafn.org>> wrote: >>=20 >> 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 = configures itself properly via dhcp6c. It also creates 2 LAN /64 = prefixes and creates 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 receives 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 devices on that LAN. I have not been able = to figure out how to make that happen. =20 >>=20 >> Clearly, manual configuration would work, but the prefix received = from the ISP can change which would raise havoc with the network. I = suspect that dhcp6s needto be run alongside dhcp6c on router B and then = the other devices run dhcp6c. However, I don't see how to get the = prefix that dhcp6c receives on router B to the dhcp6s process on router = B. I believe I am missing something, but haven't been able to find it. = Thanks, >>=20 > Speaking generally >=20 > First: I believe you=E2=80=99re looking to do DHCP prefix delegation = (dhcp-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 some sort of script which monitors the network addresses and = then updates dhcp6s.conf and restarts dhcp6s. Not very elegant though. > Second: There are valid use cases for prefixes smaller than /64, but = they 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). >=20 > -- > Louis Kowolowski = louisk@cryptomonkeys.org <mailto:louisk@cryptomonkeys.org> > Cryptomonkeys: = http://www.cryptomonkeys.com/ <http://www.cryptomonkeys.com/>; >=20 > Making life more interesting for people since 1977 >=20
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