Techniques are described for a cloud provider to provide a managed experience related to the use of virtual networks and subnets to logically group user computing resources deployed at provider substrate extensions. A cloud provider enables users to create virtual network templates used when deploying computing resources at provider substrate extensions, where such virtual network templates may include various networking, security, and other configurations to be applied to network traffic and other activity of resources deployed within an associated virtual network. Once a virtual network template is defined, a user can use the template as the basis to launch resources into the virtual network and, by extension, into provider substrate extensions associated with the virtual network. Upon receiving such a request, the provider network can manage the creation and configuration of underlying subnets, route tables, and other resource, as needed, at each of the relevant provider substrate extensions.