Block outside network access to Oracle ERP modules but allow Oracle HCM access

Summary:

We initially setup Oracle ERP with CIDR block Access Control Rules for each pod that restricts access to our Oracle instance for only users in our Network.
We are now implementing Oracle HCM and have the need to allow access to certain modules of HCM from outside of our network (Recruiting, Benefits, OTA, etc).
I need assistance on how to allow HCM access from outside the network while still restricting network access to our financial modules.

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