Few cable internet providers requires you to clone PC Mac address in order to go online through the router.
Note: It is recommended to clone MAC address from last computer which was able to go online when connected to modem.

Please launch your browser and enter http://dlinkrouter.local or http://192.168.0.1 into the address bar. Then login and follow the steps below:
Step 1: Click Setting -> Internet


Step 2: Click Advanced Setting



Step 3: Find Mac address clone field, then select one Mac address from the drop-down menu and click Save