A technique implements an administrative user interface of a backend service used to manage and administer on-premises resources, such as storage nodes of a cluster, within a private customer network. The backend service includes a browser configured to issue cross-origin resource sharing (CORS) requests among target storage nodes and a publicly-hosted web application on remote computing systems accessed via a public computer network (i.e., internet) that can be loaded on the browser within the customer network to manage and administer the on-prem resources on the private network. The technique involves the use of CORS over HyperText Transfer Protocol to access an origin that is not reachable via the public internet from a predetermined location of the browser, e.g., within the same customer network as the target storage nodes, particularly to facilitate management of the nodes.