The default userid and password is most times printed on the device. If not check the user doc. Most times it is admin/admin or such. If you changed and lost the user id/password, then you must do a factory reset of the router. See your manual to perform. Most routers you push and hold a button for 5-10 seconds on the router (may require a paper clip). Once done, the default userid/password is used and then you must reenter all of your settings as the settings are reset to the factory settings. Do change the user id and password of your router to help secure it. You may want to write the user id and password on a small piece of paper and tape it to the router (do not block any of the air vents).