What to Do If I Forget the Login Password of an AR Router

Hi . User and password admin admin does not work for me. I Have a ar129cgvw.

Please help-

Thanks

Hi, I fogot the logging details

Dear, I don't have any(console, telnet,ssh) passwords for my AR6120 router, if i use the rommon mode method and clear console passsword through that method i will lost my configurations or not?