如何设置静默登录Web应用程序？

I am creating a small business web application. All my clients access their application from their office. To make their life easy, I have put a code that will look where the request is coming from. if the request is coming from IP-address AAA then it is my customer A. I would automatically log in (on the server side) and present the customer logged in page, removing the need to supply the user and password. I am creating a small business web application.