The router can be set to factory default by pressing the Reset button of the router and resetting through the router's web-based setup page.
Reset the Router Using the Reset Button
Press the Reset button on the back of the router for 30 seconds in order to reset your router to its factory default settings. Any settings on the router will be erased and the router's IP address will become "192.168.15.1". Further, the username and password will be "admin" after you reset.
Note: Note the current settings of the device before resetting.
In order to reset the router via its web-based setup page, complete the steps in the next section.
Reset the Router Using the Web-Based Setup Page
Step 1: Access the router's web-based setup page. For instructions, click here.
Step 2: When the router's web-based setup page appears, click Administration > Factory Defaults.
Step 3: Select Yes on the Restore Factory Defaults option.