Where 2803:1920:0:1::/64 is the WAN ONU, then the network connection ONU and OLT.

/etc/dhcp/dhcpd.conf
subnet6 2803:1920:0:1::/64 {
    option dhcp6.name-servers 2803:1920:0:1::1, 2001:4860:4860::8888;

    host test{
        hardware ethernet 80:14:a8:5f:32:e4;
        fixed-address6 2803:1920:0:1::3;
        fixed-prefix6 2803:1920:0:2ff::/64;
    }

    host test2{
        hardware ethernet 80:14:a8:87:d2:15;
        fixed-address6 2803:1920:0:1::4;
        fixed-prefix6 2803:1920:0:1ff::/64;
    }
}
/etc/radvd.conf
interface eth1
{
    AdvSendAdvert on;
    AdvDefaultPreference medium;
    AdvSourceLLAddress on;
    # Advertise at least every 30 seconds
    MaxRtrAdvInterval 30;
    AdvLinkMTU 1280;
    AdvManagedFlag on;
    AdvLinkMTU 1480;
    AdvOtherConfigFlag on;
    MinRtrAdvInterval 3;
    
    prefix 2803:1920:0:1:0:0:0:0/112
    {
      AdvOnLink on;
      AdvAutonomous on;
      AdvRouterAddr on;
    };
};