Hi Andrew,
one more update:
It’s not working when changing the 40 to 80!
I changed the loopback prefix to /128 (FC00:2:2:2::A/128 instead of FC00:2:2:2::A/64) and joined the following MCAST ipv6 group on receiver (ipv6 mld join-group FF78:A80:FC00:2:2:2:0:1) but RP wasn’t learned on any node and therefore the traffic didn’t flow as well.
(*, FF78:A80:FC00:2:2:2:0:1), 00:00:03/never, RP ::, flags: SCLJ
Incoming interface: Null
RPF nbr: ::
Immediate Outgoing interface list:
GigabitEthernet1.37, Forward, 00:00:03/never
But if i was using the following group (ipv6 mld join-group FF78:A40:FC00:2:2:2:0:1) even if loopback is still configured with /128 then RP was learned properly and even traffic flowed without any problem, so i think that 40 is a fixed value and it doesn’t matter what prefix subnet is actually used for the RP itself.
(*, FF78:A40:FC00:2:2:2:0:1), 00:02:30/never, RP FC00:2:2:2::A, flags: SCLJ
Incoming interface: GigabitEthernet1.37
RPF nbr: FE80::250:56FF:FE92:3
Outgoing interface list: Null
And in addition, it doesn’t matter what i put in the 4 bits after the scope (0 is not must at all, in my example i put A), just look on the following example:
ipv6 mld join-group FF78:AA40:FC00:2:2:2:0:1
(*, FF78:AA40:FC00:2:2:2:0:1), 00:00:03/never, RP FC00:2:2:2::A, flags: SCLJ
Incoming interface: GigabitEthernet1.37
RPF nbr: FE80::250:56FF:FE92:3
Outgoing interface list: Null
And the traffic is flowing properly:
R1#ping FF78:AA40:FC00:2:2:2:0:1
Output Interface: GigabitEthernet1.12
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to FF78:AA40:FC00:2:2:2:0:1, timeout is 2 seconds:
Packet sent with a source address of 2001:1:2::1
Reply to request 0 received from 2001:3:7::7, 39 ms
Reply to request 0 received from 2001:3:7::7, 39 ms
Reply to request 0 received from 2001:3:7::7, 76 ms
Reply to request 0 received from 2001:3:7::7, 76 ms
FYI
Vladimir