Ole Troan <otroan@employees.org> wrote in <2bbba3c10911030123t66c2d4adi2d8f0fe83a6fbfb7@mail.gmail.com>: ot> Hiroki, ot> ot> > (Section 4.1) ot> > | When the router is attached to the WAN interface link it must act as ot> > | an IPv6 host for the purposes of IPv6 interface initialisation, ND ot> > | Router Discovery, Prefix Discovery and interface address assignment ot> > | ([RFC4861]/[RFC4862]). The router acts as a requesting router for ot> > | the purposes of DHCP prefix delegation ([RFC3633]). ot> > ot> > I think this description is unclear whether the router must "act as ot> > an IPv6 host" on WAN side even after interface initialization or not. ot> > More specifically, 1) we should set or not the R-bit in Neighbor ot> > Advertisement messages on WAN side, and 2) the WAN interface can ot> > respond to Router Solicitation messages or not. ot> ot> for the purposes of SLAAC, router discovery etc it should always act ot> as a host on the WAN interface. it should not reply to RS messages nor ot> set the R-bit in NAs. Thank you for the clarification. Correct me if I am wrong, but in my understanding, for router discovery and SLAAC the node must accept/process RAs and must discard received RSes. This means "acting as a host", but is there a technical reason to always set R-bit in NAs zero? A CE router has a moment of transition from a host to a router (after provisioning, for example) and vice versa as viewed from the PE router, so making R-bit depend on whether IP forwarding is enabled or not still seems reasonable to me. Even if doing so the R-bit should not prevent the CE router from router discovery or SLAAC. While pretending a host by always setting the R-bit zero would work certainly, to me there is no strong reason to disable the functionality. So, I think acting as a host with regard to RS/RA is needed on WAN interface, but NS/NA do not always need to do so. Is this a wrong idea? What I mean in writing is something like the following: | When the router is attached to the WAN interface link it must act as | an IPv6 host for the purposes of IPv6 interface initialisation, ND | Router Discovery, Prefix Discovery and interface address assignment | ([RFC4861]/[RFC4862]) except that the Router flag in Solicited | Neighbor Advertisement messages MUST be set to one if IP forwarding | is enabled; otherwise it MUST be set to zero ([RFC4861] Section 7.2.4). -- Hiroki
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