Asus RT-AC68R - Manual (Page 66)

MAC Address: MAC (Media Access Control) address is a
unique identifier for your networking device. Some ISPs
monitor the MAC address of networking devices that connect
to their service and reject any unrecognized device that
attempt to connect. To avoid connection issues due to an
unregistered MAC address, you can:
• Contact your ISP and update the MAC address associated
with your ISP service.
• Clone or change the MAC address of the ASUS wireless router
to match the MAC address of the previous networking device
recognized by the ISP.
•