[ipv6-wg] SLAAC and Broadcast RA

Dear WG,

Apologies if this mail is off topic here. I have a question about BCOP-690 wrt SLAAC

BCOP-690 says:

Using a /64 prefix from a dedicated pool of IPv6 prefixes is the most common scenario and currently the best practice. A separate block of IPv6 space is allocated for the WAN links to the end customer CPEs, so that when CPE connects to the network and performs router discovery, a /64 prefix is used to number both ends of the connection.

My understanding of this recommendation is that in an ISP scenario, each RG will be assigned a seperate /64 prefix for CPE WAN. The ISP BRAS or BNG is also expected to send periodic multicast RA.

My question is how a multicast RA can be sent to a VLAN, in which each RG is expected to have a different /64 prefix?

R-43 of TR-177 says:

The BNG MUST be configurable to send multicast RA messages that do not contain
a Prefix Information Option (PIO), in order to advertise the default router address.

R-44 says:

The BNG SHOULD support sending periodic and solicited multicast RA messages
having the unicast MAC address of the RG or of the hosts behind a bridged RG (see
RFC 6085 [26]).

Reading these two together, is it correct to say that BNG should be sending out periodic multicast RA without PIO, but RA with PIO should be sent only as a reply to an RS message from RG, with multicast IPv6 destination address but with unicast link-layer address of RG.

Thanks and Regards,

X.
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