I would like to restrict access to a cloud service based on the network where the requests are coming from. I have control over both the network, and the cloud service receiving requests from within the network. The network is behind a router, i.e. all users have the same outgoing (dynamic) IP address.
I'll provide an example: company A buys a service from company B. The service by B is hosted in the cloud. Now, A wants users to be able to use this service if and only if users are in the corporate network of A. Thus, B needs to make sure the requests from A's users originate from A's corporate network.
So what I want to do is: let company A restrict access to company B's services by requiring that all users accessing the services are within company A's network.
This would be easy if it were one network only, and I wanted to prevent outside access.