I had some MAC address before when I changed it to mac address of my router the IP addresses are now provided which relates to my locationI checked my account and it 1 MAC address registered, but this not of the WAN port on my Netgate PfSense firewall/router box. It probably belongs to one of the ONU ports (this is FTTC connection) that my home is connected to. I have switched to other routers (including home Wi-Fi routers like the Asus AC3200 that can handle multiple WANs) with this connection and there's no authentication done on MAC address. CG NAT IP addresses in the 100.xxx.xxx.xxx range are assigned randomly.
I know that YOU Broadband provides CGNAT my point is when I entered external IP addressYou Broadband does not provide public IP addresses. Your router's WAN IP assignments is a CG NAT address.
Routing to other IP addresses or domains whether internal or external (as seen when doing trace route) is done in via static or dynamic route tables in the carrier's routers and using one or more Routing Protocols like BGP, OSPF, RIP etc.
According to what I could see in my account, changing the MAC addresses registered there didn't make a difference. Also they restrict changes to once in 30 days.
In my router/firewall I can update static routes through to WAN or within LAN if required on this page.