How to change the router's MAC address

TheEther, thanks for the explanation. I appreciate that. Just to verify what you are saying...I think I understand now that since my Nighthawk is an all-in-one cable modem and router device, there is only one WAN facing MAC address and that, therefore, the software hasn't been programmed to allow MAC cloning since it would be disruptive to the ISP. Also, I think I understand from what you said, if I had a cable modem and a router as two separate devices, the router would have it's own MAC and the cable modem would also have it's own MAC. And, therefore, the feature to allow MAC spoofing would be enabled for the router since doing so wouldn't interfere with the cable modem's MAC. Now I have another question (assuming what I said above is correct)...if I did go ahead and get a separate router and a separate cable modem, would cloning the MAC of the router work to get a new IP lease even though the MAC of the cable modem would stay the same? I'm not familiar with how DHCP operates with ISP's and their cable modems, but it seems to me that, regardless of the router's MAC address, if the MAC of the cable modem does not change then the leased IP would stay the same. Thoughts?