Router default passwords and usernames

Always try using a blank username or a blank password, in combination with all the possible usernames / passwords.

Try using the full MAC address of the device as a password.

Try using the same password as that of the Wi-Fi.

If you have physical access to the router, look for any stickers with passwords on them: anything labeled key, wireless key, WPA Key, password, etc.

Try using the serial number found on bottom of the router as a password.