On Wed, Jun 16, 2021 at 11:43:36AM +0300, Andrei Borzenkov wrote:
It is explicitly prohibited to assign any IA_PD prefix to the same
interface via which this was obtained.
the requesting router MUST
NOT assign any delegated prefixes or subnets from the delegated
prefix(es) to the link through which it received the DHCP message
from the delegating router.
You are right, RFC 3633 forbids it. However, if I understand correctly this approach is the one mentioned in [1], which refers to an expired IETF draft [2] saying: As stated in [RFC 3633], "the requesting router MUST NOT assign any delegated prefixes or subnets from the delegated prefix(es) to the link through which is received the DHCP message from the delegating router", however the approach described in this document may still be useful in other DHCPv6 scenarios or non-DHCPv6 scenarios. Moreover, [RFC 3769] has no explicit requirement that avoids the approach described in this document. Furthermore, this has been tested in DHCPv6-PD implementations and worked well, so we must say that it may be implementation-dependent.
From [1], it seems that some ISPs are using this method. It would be
interesting to research what e.g OpenWRT or other OSes do. Beniamino [1] https://www.ripe.net/publications/docs/ripe-690#4-1-4---64-prefix-out-of-the-ipv6-prefix-assigned-to-the-end-user [2] https://datatracker.ietf.org/doc/html/draft-palet-v6ops-point2point-01
Attachment:
signature.asc
Description: PGP signature