I have never seen a password written under or on back of the router, The name brand routers which we all know i already told you the username and password of the ROUTER ONLY - Admin Admin and all that does id get you in the router even if you use the URL. It has nothing to do with what the OP forgot. If he set up in order to secure what he hooked up to it it is a passphrase that you would make up using numbers and letters and the longer the stronger. All you have to do is get back into the router unless like most people you also changed the password. The username will not change and stay as admin and you make up the password and then the one for the say your WIFI Passphrase for your iPhone and that is the way it works and everyone knows it, if you can't get past this, Junk the router. But a new one and start over keeping all this in mind...and a password app.