Solution required to access an ERP server in a client on-premise in a highly secured approach

Objective​ : ​ To access an ERP server in a client-on premise in a highly secured approach, once the client side user enters the ERP system credentials in a web application from one of the desktops/laptops of the respective client network which has access to the ERP server​ ​Scenario​ :​ 1. Client side user opens the website '[login to view URL]' (hosted on GCP/AWS) in a web browser in one of the desktops/laptops of the respective client network which has access to the ERP server.​ 2. Client side user enters the ERP system credentials (ERP IP, username, password) in the website.​ 3. The request is now made to the ERP Server accessible via port 3300 in client network.​ 4. As the request comes from a client side user's desktop belonging to client network, the ERP server acknowledges the same and allows access after which the ERP system data is extracted and sent back to the website server 'abc' for processing.​ How the same scenario is performed now​ : As the client side network is highly secured, the client's VPN appliance(like Fortigate) is installed & connected on the GCP/AWS instance of '[login to view URL]' and after which the above 3 steps are performed to extract the system data.​