@Clive_A I set up a port mirror of the LAN port of the Festa and capture the traffic. I see packets going out from the clients towards any internet destination IPv6 address, but nothing makes it back. I set up a port mirror on the WAN interface and I see packets going in and coming back. Inbound they are being stopped at the Festa.
LAN mirror capture:
22:47:02.989540 IP6 2604:2d80:9b03:8300:b2b9:8aff:fe43:98e9 > 2607:f8b0:4002:c11::12: ICMP6, echo request, id 35134, seq 255, length 64
22:47:03.992600 IP6 2604:2d80:9b03:8300:b2b9:8aff:fe43:98e9 > 2607:f8b0:4002:c11::12: ICMP6, echo request, id 35134, seq 256, length 64
22:47:04.995842 IP6 2604:2d80:9b03:8300:b2b9:8aff:fe43:98e9 > 2607:f8b0:4002:c11::12: ICMP6, echo request, id 35134, seq 257, length 64
22:47:05.993762 IP6 2604:2d80:9b03:8300:b2b9:8aff:fe43:98e9 > 2607:f8b0:4002:c11::12: ICMP6, echo request, id 35134, seq 258, length 64
22:47:06.991367 IP6 2604:2d80:9b03:8300:b2b9:8aff:fe43:98e9 > 2607:f8b0:4002:c11::12: ICMP6, echo request, id 35134, seq 259, length 64
WAN mirror capture:
22:42:55.969669 IP6 2604:2d80:9b03:8300:b2b9:8aff:fe43:98e9 > 2607:f8b0:4002:c11::12: ICMP6, echo request, id 35134, seq 8, length 64
22:42:55.969733 IP6 2607:f8b0:4002:c11::12 > 2604:2d80:9b03:8300:b2b9:8aff:fe43:98e9: ICMP6, echo reply, id 35134, seq 8, length 64
22:42:56.967601 IP6 2604:2d80:9b03:8300:b2b9:8aff:fe43:98e9 > 2607:f8b0:4002:c11::12: ICMP6, echo request, id 35134, seq 9, length 64
22:42:56.967630 IP6 2607:f8b0:4002:c11::12 > 2604:2d80:9b03:8300:b2b9:8aff:fe43:98e9: ICMP6, echo reply, id 35134, seq 9, length 64
22:42:57.965690 IP6 2604:2d80:9b03:8300:b2b9:8aff:fe43:98e9 > 2607:f8b0:4002:c11::12: ICMP6, echo request, id 35134, seq 10, length 64
22:42:57.965717 IP6 2607:f8b0:4002:c11::12 > 2604:2d80:9b03:8300:b2b9:8aff:fe43:98e9: ICMP6, echo reply, id 35134, seq 10, length 64
22:42:58.968812 IP6 2604:2d80:9b03:8300:b2b9:8aff:fe43:98e9 > 2607:f8b0:4002:c11::12: ICMP6, echo request, id 35134, seq 11, length 64
22:42:58.968837 IP6 2607:f8b0:4002:c11::12 > 2604:2d80:9b03:8300:b2b9:8aff:fe43:98e9: ICMP6, echo reply, id 35134, seq 11, length 64
I'm not sure how the switch ACL would be useful. I can't even add anything on that screen. Probably because i don't have a Festa switch.