Besides options @ Tools/MAC Server, is there a way to stop MT’s from advertising their MAC addresses when connected on the ISP modem? In other words, for their MAC addresses not to show on a DHCP ISP modem/router.

Let me make sure I understand what you want. A MT router gets an IP address from a ISP's modem (or the ISP itself) via DHCP, and you don't want the ISP or ISP modem to know what the MAC of the router is. Did I get that right?
If I understand your request correctly, maybe you could convince the ISP modem manufacturer not to display the MAC, but without knowing what the MAC is, there would be no communication. BTW, it does not make any difference if the router got the IP from the modem/ISP or it is static. The communication between connected devices is via the MAC. Suggest that you look up ARP.

If I did not understand your request, can you restate it?

Thank you k6ccc, no you got it right was trying to figure out if there is a way to avoid cloning of the mac address (by not knowing it ) but you are right in what you 're saying ...

All is takes is a packet sniffer on a LAN and you will quickly find every MAC on that LAN. That's the nature of Ethernet communications.

Correct ! Let me ask you this :

If a wireless device is connected to a MT which in turn is connected vie Ethernet on the ISP modem. Is there any way for this wireless device NOT to show it's MAC address in the LAN? Is there some setting on the MT that will accomplish that ? The MT receives local address from modem via DHCP on eth1 and hands out (on a different subnet) via wifi and DHCP an address to the device .

Thank you mkx!