Please don't look at ancient drafts. Look at the homenet architecture RFC: https://www.rfc-editor.org/info/rfc7368
Definitively, using any prefix longer than /64 *will not work*. The /64 has been carved in stone for many years; that's *why* you get a /48 or /56 from the ISP. > The B router receives the prefix via SLAAC and creates its own EUI-64 > address. However, that router needs to create a smaller subnet... That doesn't work. B needs to get its own /64 prefix(es) from A via DHCPv6-PD (https://www.rfc-editor.org/info/rfc8415). That's what DHCPv6-PD is for. So A will indeed need to be a DHCPv6 server on its downstream interfaces. If you run OpenWrt on A, this is apparently supported. See https://openwrt.org/docs/guide-user/network/ipv6/dhcp6c#example. But I have no experience with that. Regards Brian Carpenter On 28-Jun-21 08:32, Doug Hardie wrote: > > -- Doug > >> On 27 June 2021, at 12:41, Michael Chang <[email protected] >> <mailto:[email protected]>> wrote: >> >> If you actually want that topology, I think in practice the downstream router (B) must be at least a /64; if you got a /48 then I think you can set up A with /56s, which it can use to sub-allocate a /64 to B. >> >> https://tools.ietf.org/id/draft-ietf-homenet-arch-01.html >> <https://tools.ietf.org/id/draft-ietf-homenet-arch-01.html> >> >> The config in section 7.2 of >> https://wiki.archlinux.org/title/IPv6#Prefix_delegation_(DHCPv6-PD) >> <https://wiki.archlinux.org/title/IPv6#Prefix_delegation_(DHCPv6-PD)> might >> be what you're looking for? (See the note about `sla-len`.) > > The addresses could be done that way. However, the issue still remains, how > does router B distribute the prefix? Is using a dual dhcp6c - dhcp6s the way > to go and how does dhcp6s get the prefix from dhcp6c? > >> >> >> On Sun, Jun 27, 2021 at 12:05 PM Kristian McColm >> <[email protected] <mailto:[email protected]>> >> wrote: >> >> RFC 5375 advises against prefixes longer than /64. >> >> https://datatracker.ietf.org/doc/html/rfc5375#appendix-B.2 >> <https://datatracker.ietf.org/doc/html/rfc5375#appendix-B.2> >> >> A /48 gives you 65535 /64’s, why not use some of them? >> >> >> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ >> *From:* [email protected] >> <mailto:[email protected]> >> <[email protected] >> <mailto:[email protected]>> on behalf of Doug Hardie >> <[email protected] <mailto:[email protected]>> >> *Sent:* Sunday, June 27, 2021 2:54:01 PM >> *To:* [email protected] <mailto:[email protected]> <[email protected] <mailto:[email protected]>> >> *Subject:* Prefix delegation to sub nets >> >> 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. >> >> 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, >> >> -- Doug >> >> >> >> >> >> >> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ >> This communication is confidential. We only send and receive email on the basis of the terms set out at www.rogers.com/web/content/emailnotice <http://www.rogers.com/web/content/emailnotice> >> >> >> >> Ce message est confidentiel. Notre transmission et réception de >> courriels se fait strictement suivant les modalités énoncées dans l’avis >> publié à www.rogers.com/aviscourriel <http://www.rogers.com/aviscourriel> >> >> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ >> >> >> >> -- >> Michael Chang >
